COM 3 on IRIS hosting IMX7D not working

I tried to test the different COM Interfaces using managed code.

I used API functions to list the available Interfaces and get COM1, COM2 and COM3.
I guess, UARTA is COM1 and so on.

I see signals coming from UARTA_Tx and UARTB_Tx, but UARTC_Tx alias COM3 doesn’t work.

I also checked the registry and found out, that the pin numbers were listed correct.

It isn’t neccessary to configure the GPIO Pins to function as UART signals for UARTA or UARTB, so I guess it is also not neccessary for COM3, but maybe this is wrong.

Any idea?

With best regards


Dear @Gerhard,

UART3 pins would be overwritten by USB OTG driver. You need to disable sodimm_21 entry in the


and then Save Registry and Reboot the device and then verify UART3 is works?


You can overwrite anytime the SODIMM_21 pin alternate functionality using Gpio tool or Gpio library


You can use below alternate pins for UART3.

Please let us know if you have any other questions?