Colibri IMX8X serial UART dont work : IO error


I try to use the UART available with the colibri IMX8X ( same as colibri T20 which is currently used ) but when I try to access to any UART, I have a I/O error :

TDX Wayland with XWayland 5.1.0-devel-20210126133220+build.0 (dunfell) colibri-imx8x ttyLP3
colibri-imx8x login: root
Last login: Fri Feb  7 15:50:56 UTC 2020
root@colibri-imx8x:~# cat /dev/ttyS0
cat: /dev/ttyS0: Input/output error
root@colibri-imx8x:~# dmesg |grep UART
[    0.087194] Serial: AMBA PL011 UART driver
[    0.368823] 5a060000.serial: ttyLP0 at MMIO 0x5a060010 (irq = 46, base_baud = 5000000) is a FSL_LPUART
[    0.369851] 5a080000.serial: ttyLP2 at MMIO 0x5a080010 (irq = 47, base_baud = 5000000) is a FSL_LPUART
[    0.371020] 5a090000.serial: ttyLP3 at MMIO 0x5a090010 (irq = 48, base_baud = 5000000) is a FSL_LPUART

There is only /dev/ttyLP* but no /dev/ttyS* available in kernel log so the UART seems not detected.

Is there anything to do to activate the detection of the UART, or worse … there is no uart with colibri IMX8X :frowning:

Thanks a lot.

Greetings @f.mazur!

The available UARTs on the Colibri iMX8X are listed there: /dev/ttyLP0, /dev/ttyLP2 and /dev/ttyLP3.

By the way, /dev/ttyLP3 is the debug UART you’re using for the Linux console.

Check our developer article for more info and let us know if this works for you.


thanks for the answer. the “LP” suffix troubled me, I confuse with parallel port ( LP / LPT ).

ok I will test tomorrow with LP0 or LP1 if the communication still works as the previous colibri T20 ( I am using the same carrierboard , I wonder the electronics can be the same because the pinout is the same )


The LP suffix comes from the peripheral name, which is LPUART for Low-Power UART.

If you’re using the same carrier board, it should work just fine. Make sure to check the pins you’re using on the datasheet, though. Let me know if that works for you.

Hello @gustavo.tx ,

I’ve just tested with /dev/ttyLP0 , and it works well, the communication is available ( I was confused too because I remember that the same physical port on colibri T20 is COM2 under windows CE , so , it is the second port, and here, it is the first port ).

Sorry for the trivial question, I should read the toradex documentation before asking :stuck_out_tongue:

Thanks for the explanation for the LP suffix.



Glad that it works!

And no problem, we try to make our documentation as clear and as thorough as possible, but we’re always here to help no matter the question!

Feel free to reach out in case you have any other questions.