[GLLUG] Reading USB serial port broken

Henrik Morsing henrik at morsing.cc
Fri Sep 20 07:02:31 UTC 2019


I have an Arduino connected via USB to a PC, to read sensors around my house. It calls a Python script as a Munin plugin.

For quite some time now, and I think this possible broke after an upgrade, the Python script gets no output from ttyACM0.

Unless I run a 'tail -f' on the device from the command line! Then it works. Otherwise the script just times out getting nothing.

I'm guessing it's down to a kernel change in how it opens or signals through USB serial devices but what? Googling for a year has found nothing similar to this problem. I'm not really an expert on serial devices and even less on USB serial devices.

It's getting really frustrating now as the monitoring just never works anymore, so any help appreciated.


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