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snarksdad
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PostPosted: Tue Jan 15, 2019 9:02 pm    Post subject: Identifying serial ports Reply with quote

Hello all,
I am having a tough time getting a serial connection working. Here's the scoop:
I have an undocumented motherboard, it has 4 serial (9 pin) connections showing externally and I can't seem to figure out what tty is what or even if they are enabled. I *think* they are configured in the kernel as here is what dmesg says:

dmesg | egrep 'serial|ttyS'
Code:
[    0.128502] 00:07: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.149304] 00:08: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[    0.170099] 00:09: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 115200) is a 16550A
[    0.190894] 00:0a: ttyS3 at I/O 0x2e8 (irq = 6, base_baud = 115200) is a 16550A
[    0.211684] 00:0b: ttyS4 at I/O 0x3e0 (irq = 7, base_baud = 115200) is a 16550A
[    0.232481] 00:0c: ttyS5 at I/O 0x2e0 (irq = 11, base_baud = 115200) is a 16550A

I have tried all I can think of, turning on a getty, setserial, tio, stty and I can not get any signals whatsoever from the port(s).
I have a little LED serial monitor that shows the status of the signals and whether or not there is any data going from TX/RX and it shows nothing at all. On other Gentoo systems I have it shows DTR and RTS when I turn on a getty, but this system shows nada.

I've been looking down through the kernel config but nothing is jumping out at me...

Any ideas?

Thanks,
Snarksdad

[Moderator edit: added [code] tags to preserve output layout. -Hu]
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NeddySeagoon
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PostPosted: Tue Jan 15, 2019 10:15 pm    Post subject: Reply with quote

snarksdad,

Do a loopback test.

Get minicom installed and point it to /dev/ttyS0. Turn off all flow control. Set 8n1 and a baud rate of 115,000
Type in the minicom window. You should see nothing. Turn off Local Echo in minicom if you need to.

Link Pins 2 and 3 (Tx data and Rx data) in one of the serial ports.
Type in the minicom window again. If your wire link is on /dev/ttyS0 you will get the Tx symbols being 'echoed' back to Rx.

Move the wire link, or point minicom to another port until you have identified one.

Are the serial ports soldered to the board or on expansion brackets?
That matters as you often cannot mix serial port expansion brackets between motherboards. I've met several non interchangeable types.

What does dmidecode say about your undocumented motherboard?
It will probably need to go to a pastebin.
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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snarksdad
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PostPosted: Wed Jan 16, 2019 1:57 pm    Post subject: Reply with quote

Neddy,
Thanks for the reply. Tried the minicom loopback test and nothing.
Let me explain further. By undocumented I mean I don't have documentation. It is a proprietary board that is used in some embedded systems we have around here. There are several in use and I have access to some. The processes running on the ones in use are always connected to /dev/ttyS2 and are cabled there - so I figured I have reasonable confidence in that ports external location. From various configurations I see ttyS2-ttyS4 being used. I don't see ttyS0/S1 in use on any of these. 2 of the ports are soldered directly on the motherboard and the other 2 are on expansion card. ttyS2 is on the motherboard. Now the Gentoo/kernel are configured slightly differently on the board I have and the ones in use. For one thing, those have the usbserial driver installed and mine does not:

Code:

dmesg | egrep  'serial|ttyS'
[    0.128563] 00:07: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.149358] 00:08: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[    0.170151] 00:09: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 115200) is a 16550A
[    0.190947] 00:0a: ttyS3 at I/O 0x2e8 (irq = 6, base_baud = 115200) is a 16550A
[    0.211735] 00:0b: ttyS4 at I/O 0x3e0 (irq = 7, base_baud = 115200) is a 16550A
[    0.232528] 00:0c: ttyS5 at I/O 0x2e0 (irq = 11, base_baud = 115200) is a 16550A
[   53.763369] usbcore: registered new interface driver usbserial
[   53.763424] usbcore: registered new interface driver usbserial_generic
[   53.763431] usbserial: USB Serial support registered for generic
[   53.764032] usbserial: USB Serial support registered for FTDI USB Serial Device

lsmod:
ftdi_sio               42195  0
usbserial              28105  1 ftdi_sio

Is it possible usbserial is required for standard tty ports?

Thanks,
Snarksdad
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snarksdad
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PostPosted: Wed Jan 16, 2019 2:51 pm    Post subject: Reply with quote

snarksdad wrote:
Neddy,
Thanks for the reply. Tried the minicom loopback test and nothing.
Let me explain further. By undocumented I mean I don't have documentation. It is a proprietary board that is used in some embedded systems we have around here. There are several in use and I have access to some. The processes running on the ones in use are always connected to /dev/ttyS2 and are cabled there - so I figured I have reasonable confidence in that ports external location. From various configurations I see ttyS2-ttyS4 being used. I don't see ttyS0/S1 in use on any of these. 2 of the ports are soldered directly on the motherboard and the other 2 are on expansion card. ttyS2 is on the motherboard. Now the Gentoo/kernel are configured slightly differently on the board I have and the ones in use. For one thing, those have the usbserial driver installed and mine does not:

Code:

dmesg | egrep  'serial|ttyS'
[    0.128563] 00:07: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.149358] 00:08: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
[    0.170151] 00:09: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 115200) is a 16550A
[    0.190947] 00:0a: ttyS3 at I/O 0x2e8 (irq = 6, base_baud = 115200) is a 16550A
[    0.211735] 00:0b: ttyS4 at I/O 0x3e0 (irq = 7, base_baud = 115200) is a 16550A
[    0.232528] 00:0c: ttyS5 at I/O 0x2e0 (irq = 11, base_baud = 115200) is a 16550A
[   53.763369] usbcore: registered new interface driver usbserial
[   53.763424] usbcore: registered new interface driver usbserial_generic
[   53.763431] usbserial: USB Serial support registered for generic
[   53.764032] usbserial: USB Serial support registered for FTDI USB Serial Device

lsmod:
ftdi_sio               42195  0
usbserial              28105  1 ftdi_sio

Is it possible usbserial is required for standard tty ports?

Thanks,
Snarksdad


OK. I got it. It suddenly dawned on me to boot the same O/S as the "official" ones run and then test the ports. Turns out that 2 of the ports are not working and 2 are. Rebooted with my OS and same is true. I suppose that may be one of the reasons this board was in the parts closet. People should really label these things...

Thanks,
Snarksdad
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