Accessing UART-B i.MX7 from Linux


How can I use UART-B from Linux like a normal UART and not like the FreeRTOS/Cortex-M4 default console.

Thank you in advance !

UART_B is by active in Linux by default, see also our UART article. Our pre-built M4 firmwares just also happen to use it as default console, but that is orthogonal.

If you use the M4 firmware, you have to use a custom fdt_fixup to prevent Linux from using UART_B as documented in the FreeRTOS on the Cortex-M4 of a Colibri VF61 article. But as long as you don’t use that fdt_fixup the BSP should allow access to UART_B via /dev/ttymxc1 just fine.

Thank you for your response.
The problem is that I don’t see /dev/ttymxc1, I only have ttymxc0 and ttymxc2.

What can I do?

Thank you in advance

Which bsp version are you using? I tried the Bsp 2.7b4 20171004 and i can see the ttymxc0, ttymxc1 and ttymxc2.

My BSP version is : Colibri_iMX7_LinuxImageV2.7_20170405
I maybe used the fdt_fixup (I don’t remember), if so : how can I unfix it ?

Make sure you use a default U-Boot environment using:

env default -a

Thank you @stefan.tx , it seems I once used the fdt_fixup.
Now I can see and use ttymxc1 from linux.

Thanks for the feedback. You are welcome.