This is the code for a little robot I am working that will randomly move around the house. It is intended to be a learning exercise more than anything.

I am in the process if offloading the motor drive process to an ATmega328.

shutdown_button.py
This script needs to be run in the background at startup. It watches for BCM pin 19 to be pulled down to ground and then released. Once it detects this, it executes a graceful system shutdown. You can put the following command in /etc/rc.local at the bottom right before the exit command:

/home/pi/runtbot/venv/bin/python3 /home/pi/runtbot/shutdown_button.py &

Note the ampersand at the end. This script does not exit so it must be put in the background when started.