OSError: [Errno 13] Permission denied: '/dev/ttyACM0' - using pyserial from Python to Arduino

Question

Environment

• Linux Mint 17.1
• Python 2.7
• pyserial 2.7
• Arduino UNO rv3

Desired Behaviour

Answer 1

The permissions on the file make no difference to the user that the program runs as

When you are logged in interactively you do have permission to use the /dev/ttyACM0

When your script is running (presumably as the apache user) it does not have permission

You need to alter the permissions on the /dev/ttyACM0

See the 2nd answer here How can I programmatically set permissions on my char device for an example of altering udev permissions so the file has the correct permissions