I have a problem with comunication over ttyS0 on Colibri T30 board.
This is my test script:
s = serial.Serial('/dev/ttyS0', 230400) s.write(b'\x7e\x00\x04\x08\x52\x4e\x48\x0f')
If I boot the kernel without console=ttyS0… in the cmdline I always get “OSError: [Errno 5] Input/output error” from the test script. After that if I start and stop the serial-getty@ttyS0.service the script no longer throws an exception and everything is working correctly.
What is serial-getty@ttyS0.service doing that makes the serial usable ?
I suspect that the issue is related to the fact that the ttyS0 uart is connected to the xbee module and during bootup u-boot is sending console output to the xbee module which in turn responds with something that is totally not expected by the tty driver.