No keyboard in serial console

cmonty14 · 2022-04-10 10:30:43

Hello,

I'm connecting my router via serial cable to my desktops serial port /dev/ttyS1.

Then I start serial console using minicom or screen; when using screen I use this command:

sudo screen /dev/ttyS1 115200

After this I boot the router and can see the output in serial console.

However, I cannot enter user / password because the keyboard is not working.

When I check the log with dmesg I can see this:

[ 8591.293665] ttyS ttyS1: 1 input overrun(s)
[ 8608.025673] ttyS ttyS1: 1 input overrun(s)
[ 8614.468677] ttyS ttyS1: 3 input overrun(s)
[ 8615.475246] ttyS ttyS1: 3 input overrun(s)
[ 8619.098625] ttyS ttyS1: 4 input overrun(s)
[ 8629.231717] ttyS ttyS1: 1 input overrun(s)
[ 8636.328314] ttyS ttyS1: 1 input overrun(s)
[ 8657.398169] ttyS ttyS1: 1 input overrun(s)
[ 8661.247852] ttyS ttyS1: 2 input overrun(s)
[ 8693.758740] ttyS ttyS1: 1 input overrun(s)
[ 8719.536823] ttyS ttyS1: 2 input overrun(s)
[ 8721.130995] ttyS ttyS1: 1 input overrun(s)
[ 8731.783281] ttyS ttyS1: 3 input overrun(s)
[ 8734.015844] ttyS ttyS1: 1 input overrun(s)

When I use a laptop running Windows OS and serial client putty there's no issue.
This means the root cause is not router, serial cable, etc.

Can you please advise how to fix this issue?

THX

seth · 2022-04-10 14:12:05

https://archlinux.org/packages/extra/x86_64/putty/
Have you tried to lower the baud rate?

cmonty14 · 2022-04-10 16:38:34

Actually I have tried many different tools for serial connection, e.g. putty, picocom, cutecom.
Any tool shows the same errors.

My understanding is that I should use the same baud rate (here: 115200) as set on the router.

seth · 2022-04-10 19:57:58

Idk what you set how on the router, but the standard baud for a serial console is 9600bps - since you've an input overflow, the events are coming toofast™
This can be an issue w/ bad interrupt handling and it could also be a red herring. But I'd try a slower connection first.

Arch Linux

#1 2022-04-10 10:30:43

No keyboard in serial console

#2 2022-04-10 14:12:05

Re: No keyboard in serial console

#3 2022-04-10 16:38:34

Re: No keyboard in serial console

#4 2022-04-10 19:57:58

Re: No keyboard in serial console

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