On 25.08.22 18:42, Noel wrote: > > Modem issue ... will re-try: [Errno 16] could not open port > /dev/ttyACM0: [Errno 16] Device or resource busy: '/dev/ttyACM0' > Modem issue ... will re-try: [Errno 16] could not open port > /dev/ttyACM0: [Errno 16] Device or resource busy: '/dev/ttyACM0' > Modem issue ... will re-try: [Errno 16] could not open port > /dev/ttyACM0: [Errno 16] Device or resource busy: '/dev/ttyACM0' > ... eventually gives up trying Hi, -EBUSY is odd, because CDC-ACM does not return -EBUSY. This seems to come from the TTY layer. But just to make sure, what does lusb say about your device? Regards Oliver