Raspberry Pi CM4 built-in serial not showing up

[daniel-polak]

I'm running Companion on an industrial Raspberry Pi from Waveshare with integrated RS232 and RS485 ports, which are visible to system as /dev/ttyAMA0 and /dev/ttyAMA3. As far as I was able to tell they work alright. This module does recognize USB serial adapters, however.

This is what I've noted during troubleshooting:

• both /dev/ttyUSB* and /dev/ttyAMA* have the same permissions as per ls -l
• both pi and companion users are in the gpio user group
• in raspi-config the systems serial output is disabled as far I can tell (ie. the functionality of using the serial port as a terminal)
• I was able to "see" DMX data on the RS485 port using cat /dev/ttyAMA0
• edit 1: the stat command lists different device type numbers between the different ports:
• • 188,0 for /dev/ttyUSB0
• • 204,64 for /dev/ttyAMA0

Here is more info on the board in use https://www.waveshare.com/wiki/Compute_Module_4_PoE_Board_(B)

Any more troubleshooting tips or a possible solution is much welcome.