USART3 on STM32MP157c-dk2 configuration problem

[AZAMA]

I tried to test a UART link on the USART3 port of the STM32MP157C-DK2 board.

For that I followed the instructions of the Wiki for the modification of the Linux kernel:

• I changed the settings in "arch / arm / boot / dts / stm32mp157a-dk1.dts" to put the USART3 in status = "okay"
• I generated ".dtb" with the command "make dtbs"
• I loaded it on the board and reboot it.

But after rebooting when I do "ls -l / dev / ttySTM *" I only get the ttySTM0 (for the UART_4).

When I do "dmesg | grep ttySTM *" I get the configuration for ttySTM3 (USART_2 for Bluetooth) and ttySTM0.

After several attempts I would like to know if you would have tracks?

[Olivier GALLIEN]

Hi @AZAMA​ 

As a first sanity check, are you sure you are booting using your custom dtb ?

One useful trick is to set green led on in it in order to secure this. ( cf https://wiki.st.com/stm32mpu/index.php/How_to_cross-compile_with_the_Developer_Package )

Are you overriding the default dtb configuration or did you create a fourth option entry in /boot/extlinux/extlinux.conf ?

Hope it help

Olivier

[AZAMA]

Hi @Community member​ 

Yes actually I did first test with the green LED which was halfway concluded.

At startup the LED turns on well but in return I lose the Ethernet connection so I do not touch it anymore.

But regarding the UART no answer.

Thanks,

Armand

[Olivier GALLIEN]

Hi

Please have a look to following page :

https://wiki.st.com/stm32mpu/index.php/Trace_and_debug_scenario_-_UART_issue

Hope it help

Olivier