Using UART4 on STM32MP157A-EV1 board

[ThePUP]

2 questions here:

Is the UART4 connector active by default on the demo board or do I need to build it in?

If/when it is active, which STLinux /dev/tty is linked to the I/O path for UART4?

thank you,

-peter

[Olivier GALLIEN]

Hi @ThePUP​ 

UART4 activation depends on jumper.

See https://wiki.st.com/stm32mpu/wiki/STM32MP157C-EV1_-_hardware_description

UART4 is seen as ttySTM0 and use for Linux console by default.

Olivier

[PatrickF]

Hello,

please check https://wiki.st.com/stm32mpu/wiki/STM32MP157C-EV1_-_hardware_description#UART4_related_jumpers-_RS232_or_ST-LINK-2FV2-1-3F

UART4 is the default Linux console.

For the tty name, please have a look to https://wiki.st.com/stm32mpu/wiki/How_to_use_TTY_with_User_Terminal

Regards

[ThePUP]

Ok, thanks. That all makes sense, works as advertised but doesn't get me to my goal yet, which is to talk RS232 to one of my external serial devices using minicom on the evaluation board.

I'm currently using a well-known FTDI-USB-serial dongle plugged into a USB port which would normally allow to talk RS232 to one of my external devices. The FTDI-USB-serial dongle registers ok with the STLinux USB kernel stack when I plug it in but I have no specific driver to bind it.

I get a device MAJOR:MINOR dynamic pair when I plug it in each time, right now it's 189:132 but doing 'mknod /dev/ttyUSB0 c 189 132' does not actually bind it through to result in communications between minicom on the eval and my external device. Wired loopback at pins 2-3 on the serial cable produce no response in minicom either, so it has to be a specific driver issue between STLinux (module) and the USB-serial class IC in the dongle.

Can I do a kernel config & rebuild to get a correct module class driver set up?

thanks,

-peter

[Olivier GALLIEN · Accepted solution]

Hi @ThePUP​ 

>>Can I do a kernel config & rebuild to get a correct module class driver set up?

Yes sure. You can use Developer Package for this.

Please see

https://wiki.st.com/stm32mpu/wiki/STM32MP1_Developer_Package

Olivier

[ThePUP]

Ok, I have my USB serial dongle communicating through minicom on STLinux now.

Funny thing is, it was kernel config'd 'Y' all along but the STLinux build prep that runs the fragments update stomps all over that and a bunch of other good stuff.

thanks!

regards, -pete.