I am trying to use an USB-Serial converter with a program (a deamon) that is launched at startup on a embedded board (Odroid-XU). The deamon does not work since it fails to open the serial port /dev/ttyUSB0 reporting that the port is already in use (Device or resource busy).
Thus my first idea was that something uses the serial port shortly after the boot. BUT when I unplug and plug back the USB-Serial adapter, I have the same issue: I cannot use it for a few seconds. I checked with an oscilloscope the output of the TX port and it appears that it receives commands after being plugged or after the boot.
So what is happening here ? And what would be the solution to avoid that ?