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Linux/AM3354: Console prints are also available on UART3 port after device is boot-up

user5899310
Intellectual 460 points
Part Number: AM3354

Tool/software: Linux

Dear TI Team,

We have a design with AM3354. In our board we are using  UART1, UART2, UART3, and UART4 to communicate with our external devices. As known, UART0(ttyS0) is used as console terminal and we are able to see the debug messages on that port. However, we are also able to see the debug messages on UART3 after device is up. In our use case, we will send/receive some set of commands to/from our another board over UART3(ttyS3). While some commands are sending properly, on the other side some of them are received not properly, actually some characters are missing in the commands. Below you can see our message body.

Here, our main question is related with console terminal. Normally it must not be seen or available on UART3 port but currently it is.

We are suspecting from a wrong configuration at our side but dont know which side is wrong. Can you pls. help on to debug this issue?

Linux Version:

Linux 4.14.67-gd315a9bb00 armv7l

Distrubution:

D="arago"
NAME="Arago"
VERSION="2018.08"
VERSION_ID="2018.08"
PRETTY_NAME="Arago 2018.08"

Message Format

StartCommand(1Byte) | MessageCommand(1Byte) | Payload(4Byte) | CheckSum(1Byte) | StopCommand(1Byte)| LF(1Byte)

Console Window(UART3, UART0)

Thanks,

Regards,

Zafer Çalışkan

  • 0
    TI__Guru 55345 points

    Hello Zafer,

    You need to run the systemctl disable serial-getty@ttyS3.service command to disable the getty login prompt spawning on that UART3 port.

    root@am335x-evm:~# systemctl disable serial-getty@ttyS3.service

    Best regards,
    Kemal

  • 0 in reply to Kemal R. Shakir
    Intellectual 460 points

    Hi Kemal,

    Once i tried the command you shared, the console debug messages on UART3 has been disabled and currently we are not able to see any message on UART3(ttyS3). For example, if we send a string over a ubuntu terminal to UART3, it does not show this on another terminal which listens UART3. Do you have any comment on that?

    Note: UART3 is connected to my PC over ttyUSB0(via UART2USB convertor), and UART0 is connected over ttyUSB1.

    Regards,

    Zafer Çalışkan

  • 0 in reply to user5899310
    Intellectual 460 points
    Hi Kemal,

    Pls. ignore my last comment. UART3 is now working fine for our use case. With the command you shared above, UART3(ttyS3) only listens our sw program(not listening debug messages at the same time) which is working on ubuntu. So that now there is no abnormality related with sending/receiving wrong characters or something like that.

    Thanks for your valuable support,

    Regards,
    Zafer Çalışkan
  • 0
    TI__Guru 55345 points

    You need to run the stty -F /dev/ttyS3 115200 command and setup the UART3 baud rate, if you want to echo a message from one terminal to another.

    root@am335x-evm:~# stty -F /dev/ttyS3 115200