NSLU2-Linux
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HowTo.AddASerialPort History

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February 11, 2014, at 04:15 PM by tester12 --
Changed lines 313-316 from:

The password is "serialport". Let's see if that stops the automated wiki spam.

- justtesting

to:

The password is "serialport". Let's see if that stops the automated wiki spam.

February 11, 2014, at 04:14 PM by tester12 -- just tetsing
Added lines 314-316:

- justtesting

October 06, 2013, at 01:48 PM by Piero -- URL updated
Changed lines 293-294 from:

You can find yet another example of serial port h/w implementation at http://digilander.libero.it/marcopierpaoli/NSLU2/232_on_slug.htm

to:

You can find yet another example of serial port h/w implementation at http://p13r0.no-ip.info/g604t/RS232_howto.zip

July 13, 2012, at 02:28 AM by groost --
Changed lines 218-219 from:

\# when it's powered on, look for ': Ctrl-C to interrupt as soon as you see the ' or sit back and watch it boot and see why it fails
\# (in my case: "no /dev/sda2" wtf???) \\

to:
  1. when it's powered on, look for \'+\': Ctrl-C to interrupt as soon as you see the \'+\' or sit back and watch it boot and see why it fails
    # (in my case: "no /dev/sda2" wtf???) \\
July 13, 2012, at 02:27 AM by groost -- formatting
Changed lines 215-219 from:

To tie a bow in this: dmesg | grep tty # to find out what tty pops up when your slug shows up on your USB: in my case, /dev/ttyUSB0 sudo picocom -s 115200 -d 8 -p n /dev/ttyUSB0 # note much non-printable gibberish until the NSLU2 is powered on;

  1. when it's powered on, look for ': Ctrl-C to interrupt as soon as you see the ' or sit back and watch it boot and see why it fails
  2. (in my case: "no /dev/sda2" wtf???)
to:

To tie a bow in this:
dmesg | grep tty \# to find out what tty pops up when your slug shows up on your USB: in my case, /dev/ttyUSB0
sudo picocom -s 115200 -d 8 -p n /dev/ttyUSB0 # note much non-printable gibberish until the NSLU2 is powered on;
\# when it's powered on, look for ': Ctrl-C to interrupt as soon as you see the ' or sit back and watch it boot and see why it fails
\# (in my case: "no /dev/sda2" wtf???) \\

Changed lines 221-222 from:
  1. Solder three wires from a ribbon cable to J2, pins 2, 3, 4. On the cell phone cable, cut off all but the three wires above. If you can open the cover at the USB, snip them inside and replace the cover.
to:
  1. Solder three wires from a ribbon cable to J2, pins 2, 3, 4. On the cell phone cable, cut off all but the three wires above. \[If you can open the cover at the USB, snip them inside and replace the cover.\]
July 13, 2012, at 02:24 AM by groost -- add info about the terminal I used
Changed lines 3-4 from:

Because you can!!

to:

Because you can!! [IF you're careful at tight-space soldering around surface-mount components, and a lot of non-experts have been.]

Changed lines 212-214 from:

FWIW, I found a discussion in a webforum using this (CA-42) class of cable as a hack for yetanother device. One of their number ("Tom") had taken it upon himself to buy many different samples from many sources with a goal of understanding why some cost $1.99 and some $19.99. What he found shocked him. While the most expensive (but not always) could be argued to be over-engineering, the crappiest (and not always the least expensive) were found to have 1/5 the number of components of even the "ordinary" cable. He concluded: avoid those with injection-molded USB ends (tell-tale sign is four small "holes" where the injection took place). Prefer instead those with the "snap-over" case on the USB end, which can be pried open with a small X-acto or screwdriver. His opinion was that if it's found on ebay, it's likely to be an injection-molded, read, inferior, version. I ordered a $6 one from YallStore? (through amazon, I think) which quite accidentally proved to be one of his "good" variety. The beauty of being able to pry open the cover is that you most likely, as in my case, see the circuit board connections, the colors of the conductors, and the labels: GND, Tx, Rx, Vcc. BTW, I paid for my good luck by having Our Fine Postal Service take upwards of 3 weeks to get it to me. Remember to Tip your Postal Employees.

to:


FWIW, I found a discussion in a webforum using this (CA-42) class of cable as a hack for yetanother device. One of their number ("Tom") had taken it upon himself to buy many different samples from many sources with a goal of understanding why some cost $1.99 and some $19.99. What he found shocked him. While the most expensive (but not always) could be argued to be over-engineering, the crappiest (and not always the least expensive) were found to have 1/5 the number of components of even the "ordinary" cable. He concluded: avoid those with injection-molded USB ends (tell-tale sign is four small "holes" where the injection took place). Prefer instead those with the "snap-over" case on the USB end, which can be pried open with a small X-acto or screwdriver. His opinion was that if it's found on ebay, it's likely to be an injection-molded, read, inferior, version. I ordered a $6 one from YallStore? (through amazon, I think) which quite accidentally proved to be one of his "good" variety. The beauty of being able to pry open the cover is that you most likely, as in my case, see the circuit board connections, the colors of the conductors, and the labels: GND, Tx, Rx, Vcc. BTW, I paid for my good luck by having Our Fine Postal Service take upwards of 3 weeks to get it to me. Remember to Tip your Postal Employees.

To tie a bow in this: dmesg | grep tty # to find out what tty pops up when your slug shows up on your USB: in my case, /dev/ttyUSB0 sudo picocom -s 115200 -d 8 -p n /dev/ttyUSB0 # note much non-printable gibberish until the NSLU2 is powered on;

  1. when it's powered on, look for ': Ctrl-C to interrupt as soon as you see the ' or sit back and watch it boot and see why it fails
  2. (in my case: "no /dev/sda2" wtf???)

\\

July 13, 2012, at 01:41 AM by groost -- Add another case for CA-42, and warn about their different construction values.
Changed lines 207-211 from:
  1. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  2. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
to:

Me three: Pin 1 - NC
Pin 2 - White
Pin 3 - Green
Pin 4 - Blue
FWIW, I found a discussion in a webforum using this (CA-42) class of cable as a hack for yetanother device. One of their number ("Tom") had taken it upon himself to buy many different samples from many sources with a goal of understanding why some cost $1.99 and some $19.99. What he found shocked him. While the most expensive (but not always) could be argued to be over-engineering, the crappiest (and not always the least expensive) were found to have 1/5 the number of components of even the "ordinary" cable. He concluded: avoid those with injection-molded USB ends (tell-tale sign is four small "holes" where the injection took place). Prefer instead those with the "snap-over" case on the USB end, which can be pried open with a small X-acto or screwdriver. His opinion was that if it's found on ebay, it's likely to be an injection-molded, read, inferior, version. I ordered a $6 one from YallStore? (through amazon, I think) which quite accidentally proved to be one of his "good" variety. The beauty of being able to pry open the cover is that you most likely, as in my case, see the circuit board connections, the colors of the conductors, and the labels: GND, Tx, Rx, Vcc. BTW, I paid for my good luck by having Our Fine Postal Service take upwards of 3 weeks to get it to me. Remember to Tip your Postal Employees.

  1. Solder three wires from a ribbon cable to J2, pins 2, 3, 4. On the cell phone cable, cut off all but the three wires above. If you can open the cover at the USB, snip them inside and replace the cover.
  2. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place. [An alternative is to NOT run an exterior cable, but instead to take the case apart and connect the cable to the header only when things are so bad it's worth this effort to troubleshoot.]
May 02, 2011, at 06:07 AM by Piero --
Changed lines 280-281 from:

You can find yet another example of serial port h/w implementation at http://home.tele2.it/p13r0w3b/NSLU2/232_on_slug.htm

to:

You can find yet another example of serial port h/w implementation at http://digilander.libero.it/marcopierpaoli/NSLU2/232_on_slug.htm

Changed lines 284-294 from:

mv /dev/console /dev/console_original mv /dev/ttyS0 /dev/ttyS0_original mknod /dev/console c 1 3 (same maj/min of /dev/null) mknod /dev/ttyS0 c 4 65 (same maj/min of /dev/ttyS1) mknod /dev/COM1? c 4 64 (same maj/min of /dev/ttyS0_original) chmod 644 /dev/console chmod 644 /dev/ttyS0 chmod 644 /dev/COM1?

The "free" port is now /dev/COM1? :)

to:
  • mv /dev/console /dev/console_original
  • mv /dev/ttyS0 /dev/ttyS0_original
  • mknod /dev/console c 1 3 (same maj/min of /dev/null)
  • mknod /dev/ttyS0 c 4 65 (same maj/min of /dev/ttyS1)
  • mknod /dev/COM1? c 4 64 (same maj/min of /dev/ttyS0_original)
  • chmod 644 /dev/console
  • chmod 644 /dev/ttyS0
  • chmod 644 /dev/COM1?

The "free" port is now /dev/COM1?

November 16, 2009, at 06:38 PM by compn -- add a similar cable that worked for me
Changed lines 105-106 from:

For a no-name cable for Siemens labelled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

to:

For a no-name cable for Siemens labelled "880880-84501" "A801-2" "Made in China", (also S30880-S4501 A801-2 ) the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

June 13, 2009, at 03:11 PM by Nathan Zadoks -- Added archive.org link
June 13, 2009, at 03:11 PM by Nathan Zadoks -- Added archive.org link
Changed lines 100-101 from:

This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

to:

This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable (Dead link, use http://web.archive.org/web/20070820095200/http://www.meshcube.org/meshwiki/ModifiedMobileSerCable )

January 21, 2009, at 09:34 PM by Mike --
Added lines 199-207:

I had something a little different:

Pin 1 - NC
Pin 2 - white
Pin 3 - Green
Pin 4 - Red

December 26, 2008, at 01:23 PM by a -- a
Changed lines 239-240 from:

If you run a windows box, you can use the HyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features. Or [http://www.chiark.greenend.org.uk/~sgtatham/putty/ putty] for its all-around goodie-ness.

to:

If you run a windows box, you can use the HyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features. Or putty for its all-around goodie-ness.

December 26, 2008, at 01:22 PM by a -- a
Changed lines 239-240 from:

If you run a windows box, you can use the HyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

to:

If you run a windows box, you can use the HyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features. Or [http://www.chiark.greenend.org.uk/~sgtatham/putty/ putty] for its all-around goodie-ness.

October 25, 2008, at 11:16 PM by MXL -- typo \"of\" -> \"off\"
Changed lines 243-244 from:

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

to:

Loose wires hanging off the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

July 21, 2008, at 07:09 PM by ByronT -- Thorbjörn\'s changes
Changed lines 69-70 from:

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in Swedish but specs in english).

to:

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in Swedish but specs in english). Note that this converter is Max232-based and requires +5V to do it's magic, has points on board for adding external power. Connect TX on your board to "In" and RX to "Out" on the RS-Link.

June 16, 2008, at 01:16 PM by TimSmall -- Fix unintentional extra wiki links + a couple of spelling corrections.
Changed lines 69-70 from:

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

to:

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in Swedish but specs in english).

Changed lines 73-74 from:

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

to:

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pin-out for the NSLU2 connector.

Changed lines 76-77 from:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pinout is as follows below. Note that the DB9 connectors are assumed to be female (DTE), as opposed to male (DCE). Please see RS-232 Wiki for more details.

to:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pin-out is as follows below. Note that the DB9 connectors are assumed to be female (DTE), as opposed to male (DCE). Please see RS-232 Wiki for more details.

Changed lines 95-98 from:

Using a mobile phone data cable (DB9? serial port types)

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

to:

Using a mobile phone data cable (DB9 serial port types)

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pick-up has been reported more often with these cables.

Changed lines 105-106 from:

For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

to:

For a no-name cable for Siemens labelled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

Changed lines 113-118 from:

Nokia DKU-5 and CA-42 clone cables are available widely, and cheaply (from US$4.00 or UK£2.50 inc postage on EBay? at time of writing). Instructions for identifying each pin are available at http://buffalo.nas-central.org/index.php/Use_a_Nokia_Serial_Cable_on_an_ARM9_Linkstation

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

to:

Nokia DKU-5 and CA-42 clone cables are available widely, and cheaply (from US$4.00 or UK£2.50 including postage on EBay at time of writing). Instructions for identifying each pin are available at http://buffalo.nas-central.org/index.php/Use_a_Nokia_Serial_Cable_on_an_ARM9_Linkstation

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are available from the FTDI Online Store.

Using a USB to TTL converter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

Changed line 185 from:

Based on the picture above, it's easy to find RX and TX. Pin 7 of pl-2303 is GND, measure the resistence between pin 7 and GND can help identify GND.\\

to:

Based on the picture above, it's easy to find RX and TX. Pin 7 of pl-2303 is GND, measure the resistance between pin 7 and GND can help identify GND.\\

Changed lines 213-214 from:

Lemo, a swiss company specialized on connectors, offers tiny, yet professional, connectors that can easily be added to the back panel of the slug, right below the power connector.

to:

Lemo, a Swiss company specialized in connectors, offers tiny, yet professional, connectors that can easily be added to the back panel of the slug, right below the power connector.

Changed lines 223-225 from:

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

to:

The NSLU2 configure his serial port at 115200 baud, with 8 bits of data, no parity (8N1) If you run a Linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

Changed lines 239-240 from:

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

to:

If you run a windows box, you can use the HyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Changed lines 258-260 from:

Connect a 3K resistor between pins one and two of the serial port pads on the SLUG and the problem will go away. Any TTL level driver can drive into 3K yet the resistance is low enough to prevent AC pickup.

to:

Connect a 3K resistor between pins one and two of the serial port pads on the SLUG and the problem will go away. Any TTL level driver can drive into 3K yet the resistance is low enough to prevent AC pick-up.

June 16, 2008, at 11:58 AM by TimSmall -- Add more Nokia USB-Serial adaptor related information.
Changed lines 95-96 from:

Using a mobile phone data cable

to:

Using a mobile phone data cable (DB9? serial port types)

Changed lines 109-110 from:

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

to:

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US.

Added lines 113-114:

Nokia DKU-5 and CA-42 clone cables are available widely, and cheaply (from US$4.00 or UK£2.50 inc postage on EBay? at time of writing). Instructions for identifying each pin are available at http://buffalo.nas-central.org/index.php/Use_a_Nokia_Serial_Cable_on_an_ARM9_Linkstation

Changed lines 211-212 from:

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

to:

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, or this similar document with photos for the Buffalo NAS devices, and you can easily figure out which wire is connected to which pin.

June 10, 2008, at 08:04 AM by Christoph Pegel -- Added a section for a read only connection without level conversion
Added lines 213-218:

Read only connection without level conversion

When I bought an USB to RS232? TTL converter running with 5V by mistake, I didn't want to buy another one just to adjust the voltage. So I read about TTL and the specs said that even 5V TTL circuits would recognize voltage greater than 2.2V as a logic one. So the 3.3V on the NSLU2s? TXD will still be enough to allow the 5V TTL chip to read the signals. What I did was connecting the 5V VCC provided by USB to the VCC pin of the converter, both GNDs? (The one of the NSLU2 and the one of USB) to the GND pin and the NSLU2s? TXD pin directly to the converters RXD pin.

With this connection I can read all the output of the NSLU2, but of course I can't write anything. Maybe I will add a little circuit to convert the 5V TXD of the converter to 3.3V so the connection will be bidirectional. But for now read only is fairly enough to debug things.

May 13, 2008, at 05:23 PM by Piero --
Changed lines 261-277 from:
to:

---

You can find yet another example of serial port h/w implementation at http://home.tele2.it/p13r0w3b/NSLU2/232_on_slug.htm

To set the port free from the Linux prompt (in other words: to let my application use that serial port), I did this (tested on Unslung 6.10 only):

mv /dev/console /dev/console_original mv /dev/ttyS0 /dev/ttyS0_original mknod /dev/console c 1 3 (same maj/min of /dev/null) mknod /dev/ttyS0 c 4 65 (same maj/min of /dev/ttyS1) mknod /dev/COM1? c 4 64 (same maj/min of /dev/ttyS0_original) chmod 644 /dev/console chmod 644 /dev/ttyS0 chmod 644 /dev/COM1?

The "free" port is now /dev/COM1? :)

Added lines 279-280:
May 04, 2008, at 03:00 AM by Rob Lockhart -- cosmetic again
Changed line 90 from:
pin
to:
pin
May 04, 2008, at 02:59 AM by Rob Lockhart -- cosmetic again
Changed lines 79-89 from:
NSLU2 J2Futurlec TTL-sideRS232-sideDB9
to:
NSLU2 J2Futurlec TTL-side RS232-sideDB9
pin
1+VCC n/an/a
2RX0 RS232-0-RXD3
3TX0 RS232-0-TXD2
4GND RS232-0-GND5

Finally, NSLU2 RHS R128 (as viewing silk screen) is RX data only (TX is not present), connect this as follows:

NSLU2 R128Futurlec TTL-side RS232-sideDB9
Changed lines 91-104 from:
1+VCCn/an/a
2RX0RS232-0-RXD3
3TX0RS232-0-TXD2
4GNDRS232-0-GND5

Finally, NSLU2 RHS R128 (as viewing silk screen) is RX data only (TX is not present), connect this as follows:

NSLU2 R128Futurlec TTL-sideRS232-sideDB9
pin
2RX1RS232-1-RXD3
n/an/aRS232-1-GND5
to:
2RX1 RS232-1-RXD3
n/an/a RS232-1-GND5
May 04, 2008, at 02:58 AM by Rob Lockhart -- cosmetic again
Changed lines 79-85 from:
NSLU2 J2Futurlec TTL-sideRS232-sideDB9
pin
1+VCCn/an/a
2RX0RS232-0-RXD3
3TX0RS232-0-TXD2
4GNDRS232-0-GND5
to:
NSLU2 J2Futurlec TTL-sideRS232-sideDB9
pin
1+VCCn/an/a
2RX0RS232-0-RXD3
3TX0RS232-0-TXD2
4GNDRS232-0-GND5
Changed lines 89-94 from:
NSLU2 R128Futurlec TTL-sideRS232-sideDB9
pin
2RX1RS232-1-RXD3
n/an/aRS232-1-GND5
to:
NSLU2 R128Futurlec TTL-sideRS232-sideDB9
pin
2RX1RS232-1-RXD3
n/an/aRS232-1-GND5
May 04, 2008, at 02:33 AM by Rob Lockhart -- cosmetic
Changed lines 76-77 from:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pinout is as follows:

to:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pinout is as follows below. Note that the DB9 connectors are assumed to be female (DTE), as opposed to male (DCE). Please see RS-232 Wiki for more details.

Changed lines 79-80 from:
NSLU2 J2Futurlec TTL-sideRS232?-sideDB9?
pin
to:
NSLU2 J2Futurlec TTL-sideRS232-sideDB9
pin
Changed lines 82-85 from:
2RX0?RS232?-0-RXD3
3TX0?RS232?-0-TXD2
4GNDRS232?-0-GND5
to:
2RX0RS232-0-RXD3
3TX0RS232-0-TXD2
4GNDRS232-0-GND5
Changed lines 89-94 from:
NSLU2 R128Futurlec TTL-sideRS232?-sideDB9?
pin
2RX0?RS232?-0-RXD3
n/an/aRS232?-0-GND5
to:
NSLU2 R128Futurlec TTL-sideRS232-sideDB9
pin
2RX1RS232-1-RXD3
n/an/aRS232-1-GND5
May 04, 2008, at 02:26 AM by Rob Lockhart -- trying formatting b/c WikiSandbox is broken
Changed lines 76-78 from:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pin-out is as follows:

to:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pinout is as follows:

Changed line 88 from:
to:
May 04, 2008, at 02:25 AM by Rob Lockhart -- Added details about Futurlec serial board
Changed lines 76-77 from:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

to:

http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap. If you have access to 0.1" female headers and male test pins, this is probably the cheapest approach. This board will have two serial ports, so you can use the other one for your serial port APC UPS (if one of the not-so-smart variety). The pin-out is as follows:

NSLU2 J2Futurlec TTL-sideRS232?-sideDB9?
pin
1+VCCn/an/a
2RX0?RS232?-0-RXD3
3TX0?RS232?-0-TXD2
4GNDRS232?-0-GND5

Finally, NSLU2 RHS R128 (as viewing silk screen) is RX data only (TX is not present), connect this as follows:

NSLU2 R128Futurlec TTL-sideRS232?-sideDB9?
pin
2RX0?RS232?-0-RXD3
n/an/aRS232?-0-GND5
Changed lines 100-101 from:

This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

to:

This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

April 11, 2008, at 02:04 AM by LJR -- Elimination of AC pickup on SLUG RX line
Changed lines 233-235 from:
to:

Connect a 3K resistor between pins one and two of the serial port pads on the SLUG and the problem will go away. Any TTL level driver can drive into 3K yet the resistance is low enough to prevent AC pickup.

March 28, 2008, at 09:03 AM by nilsandreasdreicsystemsde -- There are no ttl levels on the serial port. these are LVTTL levels 5V could kill your nslu2
Changed lines 34-35 from:

RXD and TXD are TTL signals (0V/5V), not RS-232 signals (+/-12V). This means that they cannot be connected directly to a PC serial port. Converters are discussed below.

to:

RXD and TXD are (LV)TTL signals (0V/3.3V), not RS-232 signals (+/-12V). This means that they cannot be connected directly to a PC serial port. Converters are discussed below.

March 21, 2008, at 05:20 PM by Bas Wijnen -- minor fix
Added lines 34-35:

RXD and TXD are TTL signals (0V/5V), not RS-232 signals (+/-12V). This means that they cannot be connected directly to a PC serial port. Converters are discussed below.

Deleted lines 39-40:

RXD and TXD are TTL signals (0V/5V), not RS232? signals (+/-12V). This means that they cannot be connected directly to a PC serial port. Converters are discussed below.

March 21, 2008, at 05:18 PM by Bas Wijnen -- Explain how to properly add a header to the board.
Added lines 38-39:

RXD and TXD are TTL signals (0V/5V), not RS232? signals (+/-12V). This means that they cannot be connected directly to a PC serial port. Converters are discussed below.

Added lines 42-45:

Before soldering a header to the board (as opposed to separate wires), you should remove the solder from the holes. If you try to insert the header while the solder is still there, you would need to heat all holes simultaneously in order to push it through the board. Removing the solder can be done by soldering a wire to the hole (without adding extra solder) and removing it again, and possibly repeating this several times.

If you want to put the board back in the case after you connected the header, take care that it doesn't go too far through the board. If it does, it will push a bit at the case. This is enough to lock the power button in a way that prevents it being pushed.

Changed lines 60-61 from:

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

to:

(Note that there are actually 2 level converters on this chip. Don't get the wiring wrong, or you put high voltages (+/-12V) on the board!

January 23, 2008, at 11:59 AM by me -- You need 5 capacitors, not 4
Changed lines 48-49 from:

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

to:

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need five 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

October 02, 2007, at 03:24 AM by BrianZhou -- added nas-central link and hint on identifying GND
Changed lines 108-109 from:

See this hack-treo page.

to:

See this hack-treo page, and nas-central.

Added lines 160-161:

Based on the picture above, it's easy to find RX and TX. Pin 7 of pl-2303 is GND, measure the resistence between pin 7 and GND can help identify GND.
\\

September 30, 2007, at 09:31 AM by bwalle -- Added my schematics
Changed lines 58-60 from:
to:

A more friendly schematics can be found at http://www.bwalle.de/docs/nslu2-rs232.sch (EAGLE format, if you would like to edit) and http://www.bwalle.de/docs/nslu2-rs232.pdf (PDF format).

September 14, 2007, at 03:19 AM by ByronT --
Changed line 236 from:

The password is "serialport". Let's see if that stops the automated wiki spam - it has for the most part!

to:

The password is "serialport". Let's see if that stops the automated wiki spam.

September 14, 2007, at 03:08 AM by ByronT --
Changed line 236 from:

The password is "serialport". Let's see if that stops the automated wiki spam.

to:

The password is "serialport". Let's see if that stops the automated wiki spam - it has for the most part!

September 14, 2007, at 03:05 AM by ByronT -- Revise back
Deleted lines 236-237:
  • test
September 14, 2007, at 03:04 AM by ByronT -- Test
Changed line 238 from:

test

to:
  • test
September 14, 2007, at 03:01 AM by dyoung --
Changed lines 236-238 from:

The password is "serialport". Let's see if that stops the automated wiki spam.

to:

The password is "serialport". Let's see if that stops the automated wiki spam.

test

August 16, 2007, at 12:37 AM by Chris --
August 16, 2007, at 12:37 AM by Chris --
Added lines 3-4:

Because you can!!

June 07, 2007, at 05:31 PM by mhx -- Mention Lemo connectors
Added lines 182-183:

Lemo, a swiss company specialized on connectors, offers tiny, yet professional, connectors that can easily be added to the back panel of the slug, right below the power connector.

April 25, 2007, at 10:01 PM by fcarolo -- fixed links to driver download
Changed lines 178-179 from:
  1. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site
to:
  1. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Download Site
March 23, 2007, at 04:28 PM by fcarolo -- page is now password protected
Added lines 227-232:

This page is password protected.

The password is "serialport". Let's see if that stops the automated wiki spam.

March 23, 2007, at 09:37 AM by Peter Taylor -- Restored - Spam again. PLEASE PASSWORD.
Changed lines 1-3 from:

<a href=" http://www.vg.edu/title/Buy-Viagra.html ">Buy Viagra</a> <a href=" http://www.vg.edu/title/Buy-Cialis.html ">Buy Cialis</a> <a href=" http://www.vg.edu/title/Buy-Levitra.html ">Buy Levitra</a>

to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 23, 2007, at 12:35 AM by bekuul -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 21, 2007, at 12:07 AM by rvczbx -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 18, 2007, at 07:06 PM by trbdcg -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
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Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 18, 2007, at 02:12 AM by uwouto -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 17, 2007, at 03:52 AM by suampk -- Unknown
Changed lines 1-225 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html the current link for uCon is http://www.microcross.com/ucon_install.zip. It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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March 15, 2007, at 11:30 AM by Peter Taylor -- added link for uCon
Deleted line 13:
Changed lines 199-200 from:

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

to:

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html the current link for uCon is http://www.microcross.com/ucon_install.zip. It's supposed to have better logging and more features.

March 11, 2007, at 09:30 PM by PatrickSchneider -- DeSpam
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 11, 2007, at 06:19 PM by analoav -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
March 09, 2007, at 06:36 PM by analxii -- Unknown
Changed lines 1-226 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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February 21, 2007, at 06:39 PM by mhx -- Nokia CA-42 pinout
Added lines 180-181:

If the phone connector can easily be opened (as in the case of my connector which I got from ebay), then you can probably even do without a multimeter. Just have a look at the pinout of the Nokia Pop-port, and you can easily figure out which wire is connected to which pin.

February 20, 2007, at 05:49 AM by rwhitby --
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 20, 2007, at 04:39 AM by xhqofm -- Unknown
Changed lines 1-224 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 19, 2007, at 08:26 AM by aqeikw -- Unknown
Changed lines 1-224 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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February 18, 2007, at 03:58 PM by restorer -- spam removed third time
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 18, 2007, at 03:05 PM by xxlhnu -- Unknown
Changed lines 1-224 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

<a href=" http://volny.cz/spalilhost/Buy-Hydrocodone.html ">Buy Hydrocodone</a> <a href=" http://volny.cz/spalilhost/Buy-Soma.html ">Buy Soma</a>

February 18, 2007, at 08:49 AM by ismo -- spam change reverted
Changed lines 1-3 from:

<a href=" http://volny.cz/spalilhost/Buy-Hydrocodone.html ">Buy Hydrocodone</a> <a href=" http://volny.cz/spalilhost/Buy-Soma.html ">Buy Soma</a>

to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 18, 2007, at 12:13 AM by tqhxzv -- Unknown
Changed lines 1-224 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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February 17, 2007, at 01:40 AM by restorer -- Restored
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to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 16, 2007, at 10:54 PM by xsvumr -- Unknown
Changed lines 1-224 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

RS232 connection with a level-converter kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://i1.tinypic.com/2vwyzog.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

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February 03, 2007, at 11:29 PM by Phil Endecott -- Link to yet another serial voltage converter board
Changed lines 65-67 from:
to:

Yet another board is this one: http://www.futurlec.com/Mini_RS232_TTL_3V.shtml. The connectors aren't particularly convenient, but it's very cheap.

February 01, 2007, at 11:33 AM by Phil Endecott --
Changed lines 36-37 from:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cabel header can be used.

to:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cable header can be used.

Changed lines 46-47 from:

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You can safely omit the capacitor between Vcc and GND.

to:

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You may be able to omit the capacitor between Vcc and GND, though doing so could increase noise.

Changed lines 56-57 from:

RS232 connection with a kit

to:

RS232 connection with a level-converter kit

Added lines 65-69:

Using a mobile phone data cable

Some mobile phone data cables are just level converters, and may be a good choice if you can get one more cheaply than the level converter kits described above. However, note that noise pickup has been reported more often with these cables.

February 01, 2007, at 11:10 AM by Phil Endecott -- APEX also uses 115200
Changed lines 38-39 from:

By default, both RedBoot and the Linux kernel use 115200,8,N,1 settings.

to:

By default, RedBoot, APEX and the Linux kernel all use 115200,8,N,1 settings.

January 20, 2007, at 04:44 PM by flipflip --
Deleted lines 55-58:

http://helgen.oinkzwurgl.org/diskstation/rs232/

January 20, 2007, at 04:43 PM by flipflip -- Added link to detailed fotos of a level converter board for a DS-106
Changed lines 54-59 from:
to:

Photos of the steps to build such a level converter can be found here (in this case its built into a Diskstation 106): http://helgen.oinkzwurgl.org/diskstation/rs232/

http://helgen.oinkzwurgl.org/diskstation/rs232/

January 15, 2007, at 11:05 PM by davidc -- resized, sharpened and rehosted i-hacked treo cable image
Changed lines 93-94 from:

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

to:

http://i1.tinypic.com/2vwyzog.jpg

January 06, 2007, at 07:09 PM by dumfrac -- Center doesn\'t work with images that are links
Changed lines 50-51 from:

center http://isl3893.sourceforge.net/serial-max3232.gif

to:

http://isl3893.sourceforge.net/serial-max3232.gif

Changed lines 93-94 from:

center http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

to:

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

January 06, 2007, at 07:07 PM by dumfrac -- Center pictures
January 06, 2007, at 07:07 PM by dumfrac -- Center pictures
Changed lines 32-33 from:
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http://isl3893.sourceforge.net/serial-max3232.gif

to:

center http://isl3893.sourceforge.net/serial-max3232.gif

Changed lines 93-94 from:

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

to:

center http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

January 06, 2007, at 07:00 PM by dumfrac --
Changed lines 193-194 from:

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R? IC which is used inside the cable.

to:

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R IC which is used inside the cable.

January 06, 2007, at 06:57 PM by dumfrac -- Fix FTDI link (forgot double square brackets)
Changed lines 77-78 from:

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R | FTDI Online Store].

to:

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the FTDI Online Store.

January 06, 2007, at 06:56 PM by dumfrac -- Clarify TTL-232R-3V3 6-pin connector usage and make FTDI prettier
Changed lines 77-78 from:

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which is not directly compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

to:

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which can be used by swapping the pins to make it compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from the [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R | FTDI Online Store].

January 06, 2007, at 06:50 PM by dumfrac -- Force RxD not to be a wiki link
Changed lines 79-80 from:

Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

to:

Using a USB to TTL conveter is nice because it seems to solve the floating RxD problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

December 31, 2006, at 04:11 PM by ths -- Revert vandalism
Changed lines 1-4 from:

Hello, nice site look this: <a href= http://sesso-gratis.sex-italy.org/sesso-gratis.html >sesso gratis Orso</a> [url=http://sesso-gratis.sex-italy.org/sesso-gratis.html]sesso gratis Orso[/url]

End ^) See you

to:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cabel header can be used.

By default, both RedBoot and the Linux kernel use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You can safely omit the capacitor between Vcc and GND.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

RS232 connection with a kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which is not directly compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R? IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
December 31, 2006, at 12:09 PM by Ayden --
Changed lines 1-215 from:

Why Add A Serial Port?

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • See any kernel panics.

The rest of this page describes how to connect up your internal serial port.

Pinout of the J2 serial port

Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cabel header can be used.

By default, both RedBoot and the Linux kernel use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the MAX3232 from Maxim/Dallas Semiconductor. In addition to the MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the MAX3232 is available on the Maxim/Dallas Semiconductor page. You can safely omit the capacitor between Vcc and GND.

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

RS232 connection with a kit

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

If you wish to buy a kit then the CompSys A232DBH3v Max232 adapter kit (3V version) has been used with no problems. See Rod Whitby's guide for more details.

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

USB connection

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which is not directly compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

See this hack-treo page.

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225, VX4500, VX4600, VX600
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.
    For Nokia 3285 and 5185 Cable:

    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For LG 1200 Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield

    For Future Dial Cable 22:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - White
    Pin 4 - Green & Shield (twisted together)

    For Nokia DKU-5 or CA-42 (WT048000317):
    This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

    From the USB/PC point of view:
    GND: White (maybe also Yellow)
    TX: Red
    RX: Blue (apparently not Green)

    You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

    The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

    Assuming your colours are the same as mine, then:

    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Blue
    Pin 4 - White

  2. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  3. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  4. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  5. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  6. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  7. Windows users will need a Windows driver for the Prolific USB-to-Serial adaptor, available at the Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1) If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1).

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R? IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
to:

Hello, nice site look this: <a href= http://sesso-gratis.sex-italy.org/sesso-gratis.html >sesso gratis Orso</a> [url=http://sesso-gratis.sex-italy.org/sesso-gratis.html]sesso gratis Orso[/url]

End ^) See you

December 21, 2006, at 12:42 PM by Phil Endecott -- Mention FTDI wire-ended cable
Changed lines 77-80 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3), which does work.

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

to:

FTDI sell a couple of reasonably cheap USB to 3v3 serial cables, part numbers TTL-232R-3V3 and TTL-232R-3V3-WE, which are known to work. The TTL-232R-3V3 has a 6 pin connector which is not directly compatible with the NSLU2, while the -WE version has bare wires that you can connect up as you like. They are avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

December 21, 2006, at 12:31 PM by Phil Endecott -- Improve introduction
Changed lines 3-10 from:

Adding a serial port will allow you to:

  • Access RedBoot, the boot-loader - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting. *using onboard serial only, not USB
  • Log in, if a getty is running on the serial port, which it normally is.
to:

There are two ways that you can connect a serial port to your NSLU2: you can plug a USB-to-Serial cable in to one of its USB ports, or you can open the case and make use of the internal serial port.

Using a USB-to-Serial cable will allow you to:

  • Interface to peripherals with RS232 ports.
  • Log in, if you run a getty process on the port.

See USB2Serial for more information about using these cables.

There are, however, some things that you can only do using the internal serial port. You can:

  • Access RedBoot and/or APEX, the boot-loaders - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
Changed lines 21-22 from:
  • Interface to peripherals with RS232 ports - though a better alternative for this is normally to use one of the NSLU2's USB ports and a USB2Serial cable.
to:

The rest of this page describes how to connect up your internal serial port.

December 21, 2006, at 12:47 AM by Peter Enzerink --
Changed line 132 from:

For Nokia DKU-5 (WT048000317):\\

to:

For Nokia DKU-5 or CA-42 (WT048000317):\\

October 19, 2006, at 08:05 PM by Bullfrog --
Changed lines 70-71 from:

This is avaliable from ftdichip shop

to:

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

October 19, 2006, at 08:04 PM by Bullfrog --
Changed lines 70-71 from:

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

to:

This is avaliable from ftdichip shop

October 14, 2006, at 01:35 PM by Reedy Boy --
Changed lines 70-71 from:

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R here

to:

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R

October 14, 2006, at 01:34 PM by Reedy Boy --
Changed lines 68-70 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R, which does work. Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3), which does work.

This is avaliable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R here

Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

October 14, 2006, at 01:32 PM by Reedy Boy --
Changed line 68 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R from here],

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R,

October 14, 2006, at 01:31 PM by Reedy Boy --
Changed line 68 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R],

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R from here],

October 14, 2006, at 01:30 PM by Reedy Boy -- Wikify [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R]
Changed line 68 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R,

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the [http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R],

October 11, 2006, at 06:49 AM by krakker -- added a serial converter kit
Added lines 48-49:

A really good kit is the RS Link from jescab (Swedish...) RS-Link (page in swedish but specs in enlish).

September 06, 2006, at 05:39 AM by Dave Hrynkiw -- Warning regarding that there are 2 serial level shifters on the chip
Changed lines 43-45 from:
to:

(Note that there are actually 2 level converters on this chip. Don't make the mistake of wiring the inputs to the 1st converter, and the outputs to the 2nd!

August 24, 2006, at 01:25 PM by phil endecott -- Make FTDI link unpretty again, so that it is useable. (Gordon: external links don\'t get approved, so the URL must be visible so that it can be copied&pasted)
Changed line 64 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the FDTI On-Line Store,

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R,

August 24, 2006, at 02:18 AM by Gordon -- Make FDTI On-Line Store link a little prettier
Changed line 64 from:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R,

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from the FDTI On-Line Store,

August 23, 2006, at 04:48 AM by Gordon -- Minor TTL-232R-3V3 edits
Changed lines 65-66 from:

which does work. The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

to:

which does work. Using a USB to TTL conveter is nice because it seems to solve the floating RxD? problem which prevents the NSLU2 from booting (see the section titled, "Serial port and picking-up mains: a word of caution" on this page). The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

Deleted line 170:
Changed lines 179-182 from:

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process.

This is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

to:

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process. This problem does not seem to occur with a TTL-232R-3V3 (see above) USB to TTL converter which makes sense, because the serial port of the NSLU2 is always connected to the FT232R? IC which is used inside the cable.

This problem is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

August 23, 2006, at 03:52 AM by Gordon -- Describe connection procedure for the TTL-232R-3V3
Changed lines 64-66 from:

You can get a reasonably cheap USB to 3v3 serial cable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R, which should work. It has a 6 pin connector from which you'll have to patch up appropriate connections to the NSLU2's 4-pin header.

to:

You can get a reasonably cheap USB to 3v3 serial cable (TTL-232R-3V3) from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R, which does work. The following steps describe how to hook up the TTL-232R-3V3 6-pin connector to the NSLU2 4-pin serial port.

  1. Carefully remove the female pins from the TTL-232R-3V3 6-pin connector by lifting the black tabs that hold each pin in place. A small flat-head screwdriver or a razor blade works well.
  2. Connect the orange wire of the TTL-232R-3V3 to pin 2 of the NSLU2 serial port, the yellow wire to pin 3, and the black wire to pin 4. Don't connect pin 1 on the NSLU2, and the brown, green, and red wires of the TTL-232R-3V3. I reused the black 6-pin connector to hold the socket pins in place.
August 19, 2006, at 10:19 AM by zzdomi -- Broken link for pl2303 drivers downlad
Changed lines 72-73 from:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

to:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

August 09, 2006, at 03:08 AM by NeoMatrixJR --
Changed lines 7-8 from:
  • View kernel messages while the NSLU2 is booting.
to:
  • View kernel messages while the NSLU2 is booting. *using onboard serial only, not USB
Changed lines 173-174 from:

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu.

to:

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu. Or you can download uCon from: http://www.microcross.com/html/micromonitor.html (do a find for uCon). It's supposed to have better logging and more features.

July 31, 2006, at 01:25 PM by Egor Zindy -- oops! my privoxy changed all the instances of \\\"open\\\" into \\\"PrivoxyWindowOpen\\\", changed back...
Changed line 163 from:
 cu: PrivoxyWindowOpen?(/dev/ttyS0): Permission denied\\
to:
 cu: open (/dev/ttyS0): Permission denied\\
July 31, 2006, at 01:14 PM by Egor Zindy -- added a paragraph about booting issues
Changed line 163 from:
 cu: open (/dev/ttyS0): Permission denied\\
to:
 cu: PrivoxyWindowOpen?(/dev/ttyS0): Permission denied\\
Changed lines 175-192 from:
to:

Serial port and picking-up mains: a word of caution

Loose wires hanging of the serial connector can prevent the slug from booting properly. When this happens, the power LED stays orange and linux never boots. If a serial cable is plugged in and a serial terminal run, pressing enter will resume the booting process.

This is caused by the mains being picked up by wire and injected into the RX pin as a 1.6V, 50Hz signal (measured with a scope).

There are two cases where this could be a problem:

  • Problem will occur when the serial cable is left unplugged at the PC end.
  • Problem can occur if the serial port is shifted to a connector at the back of the slug... and left unplugged.

This illustrates the second case: User drilled a hole under the power connector and fitted a 2.5mm stereo jack socket to bring the serial lines to the back. The NSLU2 will boot when the socket is used, but not when the serial cable is unplugged from the NSLU2. The 10cm cables between the socket and the PCB connector were causing the problem.

The following experiment was conducted to trace the problem:

  • NSLU2 booted normally when RX (pin 2) was connected to GND (pin 4).
  • NSLU2 booted normally when RX (pin 2) was connected to VCC (pin 1, via a 4.7K resistor).
  • NSLU2 didn't boot when a 10cm long twisted pair stub was connected between VCC and RX.
July 19, 2006, at 07:52 PM by Phil Endecott -- Mention FTDI\'s USB-to-3v3 cable
Added lines 64-66:

You can get a reasonably cheap USB to 3v3 serial cable from http://apple.clickandbuild.com/cnb/shop/ftdichip?op=catalogue-products-null&prodCategoryID=47&title=Cables%3A+TTL-232R, which should work. It has a 6 pin connector from which you'll have to patch up appropriate connections to the NSLU2's 4-pin header.

June 10, 2006, at 12:06 PM by eFfeM -- added advice to open and study connector
Added line 87:

Below are a number of cables listed with a description of the colored wires that you need. Since clone cables might use different colors I recommend googling for the connector layout of the mobile phone you used and carefully pry the cable open (at the phone connector) and study the pinning/cabling.\\

Added line 89:

\\

June 10, 2006, at 05:34 AM by eFfeM -- added warning that for cu /dev/ttyS0 should be owned by uucp
Added lines 156-163:

If cu is giving you

 cu: open (/dev/ttyS0): Permission denied
cu: /dev/ttyS0: Line in use

even if running as root, you might want to check if /dev/ttyS0 is owned by uucp. If not do a chown uucp /dev/ttyS0

May 20, 2006, at 01:34 PM by Lurch -- Aded link to USB2Serial page
Changed lines 13-14 from:
  • Interface to peripherals with RS232 ports - though a better alternative for this is normally to use one of the NSLU2's USB ports and a USB-to-Serial cable.
to:
  • Interface to peripherals with RS232 ports - though a better alternative for this is normally to use one of the NSLU2's USB ports and a USB2Serial cable.
May 14, 2006, at 12:31 AM by Adam Nielsen -- Addition of DKU-5 mobile phone cable pinouts
Changed lines 117-136 from:
to:

For Nokia DKU-5 (WT048000317):
This cable seems easier to get in Australia (I got mine off eBay.) There are generic versions available, so the colours might be different. You will probably need a multimeter to find the correct wires.

From the USB/PC point of view:
GND: White (maybe also Yellow)
TX: Red
RX: Blue (apparently not Green)

You can check these with a multimeter - the voltage between GND and TX is 3.3V, and the voltage sags slightly if you send a lot of data out over the port (e.g. by holding a key down in a terminal emulator.) You can also hook up a speaker between these two wires and it should click whenever you transmit a character/press a key.

The voltage between GND and RX is about 2.5V. If you connect TX and RX together (join the Red and Blue wires) you should see anything you type echoed back to the screen (possibly appearing twice if you have local-echo enabled in your terminal emulator.) For me, this worked when I connected Red to either Blue or Green, but only Blue worked when connected to the WRT54G - nothing was received through the Green wire.

Assuming your colours are the same as mine, then:

Pin 1 - NC
Pin 2 - Red
Pin 3 - Blue
Pin 4 - White

April 29, 2006, at 03:14 PM by Patrick Schneider -- Added Driver Download Link for PL2303 (Win XP64 is supported now btw)
Changed lines 69-70 from:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

to:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Driver Download) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

April 01, 2006, at 10:17 PM by Charles Turner -- Added info about the Nokia DLR-3 cable...
Added lines 60-61:

The Nokia DLR-3 cable is the same hardware, but older Windows95 driver software (which you don't need). I found my cable through Froogle for $2.00 US, so it's gotta be the cheapest serial mod on this page!

February 27, 2006, at 09:47 PM by Michiel Leegwater -- Link to set of datasheets
Changed lines 67-68 from:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet [Access Denied!]) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

to:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet ) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

February 25, 2006, at 04:47 PM by eFfeM -- added cable pinout
Changed lines 54-55 from:

The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html

to:

The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html
If your cable is not powered from the DSub-side you have to connect pin 4 to J2 pin 1 (+3.3V).
For a noname cable for Siemens labeled "880880-84501" "A801-2" "Made in China", the BLACK wire is GND, the RED wire is needed for power, the YELLOW cable is data out (TX) and the GREEN cable is data in (RX)

February 25, 2006, at 12:56 PM by eFfeM -- added 8N1
Changed line 128 from:

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data.

to:

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data, no parity (8N1)

February 25, 2006, at 09:50 AM by eFfeM -- added cdrom audio cable text (kudo\'s to nail for suggesting this)
Changed lines 27-28 from:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder.

to:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder. First action for any of the methods below is to mount such a header (you didn't consider soldering your cable directly to the board, did you?). After that construct a cable to connect to this header using one of the methods below. As an easy starter one can cut a CDROM audio cable in two. That will give you a four pin connector with some wire to connect to. Alternately a flat cabel header can be used.

February 22, 2006, at 05:33 PM by Reedy Boy -- Formatted Links at bottom of page
Changed lines 144-145 from:

[http://groups.yahoo.com/group/nslu2-linux/message/87][http://groups.yahoo.com/group/nslu2-linux/message/1411] [http://www.rwhitby.net/nslu2/serial.html] - Guide for adding Serial Port with Pictures

to:
  • http://groups.yahoo.com/group/nslu2-linux/message/87
  • http://groups.yahoo.com/group/nslu2-linux/message/1411
  • http://www.rwhitby.net/nslu2/serial.html - Guide for adding Serial Port with Pictures
February 22, 2006, at 05:32 PM by Reedy Boy -- Added a link to a pictured guide
Added line 145:

[http://www.rwhitby.net/nslu2/serial.html] - Guide for adding Serial Port with Pictures

February 11, 2006, at 04:02 PM by endecotp -- Why add a serial port, 3v3-RS232 board from picbasic.it
Added lines 1-16:

Why Add A Serial Port?

Adding a serial port will allow you to:

  • Access RedBoot, the boot-loader - though you can also TelnetIntoRedBoot.
  • View kernel messages while the NSLU2 is booting.
  • Log in, if a getty is running on the serial port, which it normally is.
  • See any kernel panics.
  • Interface to peripherals with RS232 ports - though a better alternative for this is normally to use one of the NSLU2's USB ports and a USB-to-Serial cable.

Pinout of the J2 serial port

Deleted line 17:
Pinout of the J2 serial port
Changed lines 27-28 from:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a series of solder pads.

to:

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a row of holes, filled with solder.

Changed lines 48-50 from:

The Siemens S/C25, S/C/M35 or S/SL/ME/M45 all operate at 3.3V and the RS232 data cables are compatible.

to:

Another board that works is this one, from Italy: http://www.picbasic.it/interfacce/page2.html . The lead has the right pinout for the NSLU2 connector.

The Siemens S/C25, S/C/M35 and S/SL/ME/M45 phones all operate at 3.3V and the RS232 data cables are compatible.

Added lines 133-136:

picocom is another simple terminal program:

 picocom -b 115200 /dev/ttyS0
November 14, 2005, at 11:13 AM by jr --
Added lines 39-40:

You can also use Nokia DLR-3P data cable. Just cut off connector and wire RED to J2 pin 1 (+3.3V), GREEN to J2 pin 2 (RXD), GRAY to J2 pin 3 (TXD) and BLACK+SHIELD to J2 pin 4 (GND). Since this cable is normally powered by phone you need to connect J2 pin 1.

October 27, 2005, at 09:27 AM by zoobab -- http://isl3893.sourceforge.net/serial-max3232.gif
Added lines 24-28:

Like here:

http://isl3893.sourceforge.net/serial-max3232.gif

October 11, 2005, at 09:53 PM by rpedde -- add info for futuredial cable 22
Changed lines 53-55 from:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction MA-8710C for Siemens mobiles"

to:
   - Cable 22 (For Nokia 3100, 3200, 3585i, 3588 and others with Nokia 14-pin pop-port)

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600.", "MobileAction MA-8710C for Siemens mobiles" and "Future Dial Cable 22"

Changed lines 83-89 from:
to:

For Future Dial Cable 22:
Pin 1 - NC
Pin 2 - Orange
Pin 3 - White
Pin 4 - Green & Shield (twisted together)

September 23, 2005, at 08:31 PM by tylerl --
Changed lines 41-42 from:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

to:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet [Access Denied!]) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

September 07, 2005, at 09:07 AM by alecv -- Siemens cables
Changed lines 41-44 from:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems.

to:

Most of the cheap cables are based on a Prolific PL2303 chipset (PL2303 datasheet) which is supported under Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems. A data cables from the Siemens C25/35/45 works too. The cables from the old models (i.e. C25) costs a 2..3$.

July 13, 2005, at 11:33 PM by repvik -- Prolific chipset unsupported in WinXP x64
Changed line 42 from:

Windows and Linux. A third party Nokia data cable for a 8000 series phone has been used

to:

Windows (Not Windows XP x64 yet!) and Linux. A third party Nokia data cable for a 8000 series phone has been used

June 12, 2005, at 07:44 AM by tman --
Changed lines 20-21 from:

RS232 connection without a kit

to:

RS232 connection without a kit

Changed lines 24-25 from:

RS232 connection with a kit

to:

RS232 connection with a kit

Changed lines 34-35 from:

USB connection

to:

USB connection

Changed line 52 from:
   - LG Models 1200, VI5225?,VX4500?, VX4600?, VX600?
to:
   - LG Models 1200, VI5225, VX4500, VX4600, VX600
Changed lines 56-57 from:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction MA-8710C for Siemens mobiles"

to:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction MA-8710C for Siemens mobiles"

Changed line 82 from:

Pin 4 - Shield

to:

Pin 4 - Shield\\

Changed lines 97-98 from:

Accessing the terminal

to:

Accessing the terminal

Added line 101:
Added line 103:
Changed lines 107-108 from:

Acknowledgements

to:

Acknowledgements

March 05, 2005, at 08:43 PM by dmahurindmaorg --
Changed lines 45-46 from:

A cheap cable can be purchased at Radio Shack. It is the "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185."

to:

A cheap($20) cable can be purchased at Radio Shack. The Future-Dial cables have a "dongle" in the middle that has the Prolific usb-serial chip.

Changed line 47 from:

UPC 040293169640

to:

http://www.i-hacked.com/images/stories/Treo650/Treo650-Cablepinout-thmb.jpg

Changed line 49 from:

RS# 170-0787

to:

See this http://www.i-hacked.com/content/view/66/47/ hack-treo page.

Changed lines 51-53 from:

This item has been discontinued and is on closeout so stock will be limited.

Another compatible cable is the "Radio Shack Module Phone Data Cable for Audiovox Models 8200, 8500 and 8600" also from Radio Shack

to:

Compatible Radio Shack (Future Dial) "Mobile Phone Data Cables":

   - LG Models 1200, VI5225?,VX4500?, VX4600?, VX600?
   - Audiovox Models 8200, 8500 and 8600
   - Nokia Models 3285 and 5185
Added lines 69-74:

Pin 3 - Orange
Pin 4 - Shield

For LG 1200 Cable:
Pin 1 - NC
Pin 2 - Red \\

March 01, 2005, at 12:13 AM by ByronT --
Changed line 56 from:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "Mobile Action MA-8710C for Siemens mobiles"

to:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction MA-8710C for Siemens mobiles"

Changed line 72 from:

For Siemens Mobile Action MA-8710C Cable:\\

to:

For Siemens MobileAction MA-8710C Cable:\\

Changed line 95 from:
 cu -l /dev/ttyS0 -s 115200 (for COM 1).
to:
 cu -l /dev/ttyS0 -s 115200 (for COM1).
February 28, 2005, at 11:55 PM by ByronT --
Changed line 56 from:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction? MA-8710C for Siemens mobiles

to:

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "Mobile Action MA-8710C for Siemens mobiles"

Changed line 72 from:

For Siemens MobileAction? MA-8710C Cable:\\

to:

For Siemens Mobile Action MA-8710C Cable:\\

Changed line 95 from:
 cu -l /dev/ttyS0 -s 115200 (for COM1?).
to:
 cu -l /dev/ttyS0 -s 115200 (for COM 1).
February 14, 2005, at 03:24 AM by tman --
Changed lines 1-103 from:

Describe AddASerialPort here.

to:
Pinout of the J2 serial port
Pin 13.3V (pin 1 has a white stripe next to it)
Pin 2RXD (from serial terminal program to NSLU2)
Pin 3TXD (from NSLU2 to serial terminal program)
Pin 4GND

Pin 1 is the left-hand pin.

NB: In the photo above, a set of header pins has been attached to J2. As sold, J2 consists only of a series of solder pads.

By default, both RedBoot and the Linux kernel use 115200,8,N,1 settings.

Set DTR drop time to 0, and "modem has DCD line" to no.

Make sure that your terminal program does not send a modem init string and that you have set it to software flow control, not hardware.

RS232 connection without a kit

If you wish to construct a level converter from scratch and not buy a kit then a suitable level converter chip is the http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1068 MAX3232 from http://www.maxim-ic.com Maxim/Dallas Semiconductor. In addition to the http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1068 MAX3232, you will need 4x 0.1μF capacitors. The diagram to wire up the capacitors to the http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1068 MAX3232 is available on the http://www.maxim-ic.com Maxim/Dallas Semiconductor page. You can safely omit the capacitor between Vcc and GND.

RS232 connection with a kit

If you wish to buy a kit then the CompSys http://www.compsys1.com/workbench/On_top_of_the_Bench/Max233_Adapter/max233_adapter.html A232DBH3v Max232 adapter kit has been used with no problems. See http://www.rwhitby.net/nslu2/serial.html Rod Whitby's guide for more details.

The Siemens S/C25, S/C/M35 or S/SL/ME/M45 all operate at 3.3V and the RS232 data cables are compatible. This cable is used on another embedded project. Take a look at: http://www.meshcube.org/meshwiki/ModifiedMobileSerCable

The cable should be powered from the DSub-side (PC/Terminal). The pins which are used are 1 (GND), 5(TX), 6(RX). The Siemens-Handy-connector is shown at http://www.hardwarebook.net/connector/cellular/siemens_c25_s25.html

USB connection

A USB based data cable for a mobile phone is another possibility. Most (if not all) of these cables are nothing more than an USB to serial port adapter, and as most mobile phone today are using 3.3V anyway they already have the right signal levels.

Most of the cheap cables are based on a Prolific PL2303 chipset (http://tech.prolific.com.tw/visitor/fcabdl.asp?fid=17151518 PL2303 datasheet) which is supported under Windows and Linux. A third party Nokia data cable for a 8000 series phone has been used with no problems.

A cheap cable can be purchased at Radio Shack. It is the "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185."

UPC 040293169640

RS# 170-0787

This item has been discontinued and is on closeout so stock will be limited.

Another compatible cable is the "Radio Shack Module Phone Data Cable for Audiovox Models 8200, 8500 and 8600" also from Radio Shack

Installation of "Radio Shack Mobile Phone Data Cable for Nokia Models 3285 and 5185.", "Radio Shack Mobile Phone Data Cable for Audiovox Models 8200, 8500 and 8600." and "MobileAction? MA-8710C for Siemens mobiles

  1. Open the connector that connects to the cell phone, You only need 3 wires, and these connect to J2.

    For Nokia 3285 and 5185 Cable:
    Pin 1 - NC
    Pin 2 - Orange
    Pin 3 - Red
    Pin 4 - Brown/Shield

    For Audiovox 8200, 8500 and 8600 Cable:
    Pin 1 - NC
    Pin 2 - Yellow
    Pin 3 - Orange
    Pin 4 - Shield

    For Siemens MobileAction? MA-8710C Cable:
    Pin 1 - NC
    Pin 2 - Red
    Pin 3 - Black
    Pin 4 - Shield


  1. Solder three wires from a ribbon cable to J2. On the cell phone cable, cut off all but the three wires above.
  2. Carve a slot just below the power connector hole in the back panel that will allow you to insert the strain relief through the power supply hole and slip it down into place.
  3. Run the cable through the power supply hole, and solder the other ends of the 3 wires to the phone data cable. You can shrink wrap, or tape the wires.
  4. Slide the strain relief down into the slot, and slide the board back into the case. The power supply socket will lock the strain relief in place.
  5. Plug the USB connector into your Linux box. Start minicom and set the port to /dev/ttyUSB0 115200 8N1. Power up and you will see a '+' printed. Ctrl+C will get a RedBoot prompt, or leave it alone and watch it boot.
  6. Windows users will need a http://tech.prolific.com.tw/visitor/fcabdl.asp?fid=31604505 Windows driver for the Prolific USB-to-Serial adaptor, available at the http://tech.prolific.com.tw/ Prolific Technology Inc Support Site

Accessing the terminal

The NSLU2 configure his serial port at 115200 bauds, with 8 bits of data. If you run a linux a box, you can use the UUCP for talking to the nslu2 by the serial port:

 cu -l /dev/ttyS0 -s 115200 (for COM1?).

If you run a windows box, you can use the hyperTerminal program located in accessory->Communication in the start menu.

Acknowledgements

Thanks to paulbart, kju, m. allan noah, guidoz and Gerald L Clark.

[http://groups.yahoo.com/group/nslu2-linux/message/87][http://groups.yahoo.com/group/nslu2-linux/message/1411]