Could not open port error immediately after plugging in Arduino on Arch Linux

user_1902779 0
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I am using PlatformIO for programming and Arduino Mega and an Arduino Uno. I have them hooked up through serial, so I have to disconnect them from each other every time I want to program them. I also unplug them from the computer so that I don't accidentally fry them while moving wires around.

Every time I plug one or the other back in and try to program it immediately, I get this error message:

*** [upload] could not open port /dev/ttyACM0: [Errno 16] Device or resource busy: '/dev/ttyACM0'

If I wait for about a minute and try again, then the code will be uploaded no problem. What could be causing this?

platformio archlinux arduino
1 Answers

ModemManager might be the cause of your troubles. Try disabling it with, e.g. pkill -STOP ModemManager (continue the process with -CONT).

ModemManager is a (fantastic) piece of software that makes your 3G dongles work automagically. Because the Arduino appears as a serial modem, ModemManager tries to take control over it.

You can stop ModemManager from doing that by attaching a certain variable to your device. See the documentation for details. Essentially, create a udev rule, e.g. /etc/udev/rules.d/99-ttyacms.rules with the following content:

ATTRS{idVendor}=="0ca6" ATTRS{idProduct}=="a050", ENV{ID_MM_DEVICE_IGNORE}="1

Of course, you need to use your IDs. Use lsusb to find those values.

After you have created this file, reload udev with something like sudo udevadm control --reload-rules

user_20157680
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