companion computers for ardupilot

1. Good step by step tutorial but no video tutorial.

https://github.com/ArduPilot/ardupilot_wiki/blob/master/dev/source/docs/raspberry-pi-via-mavlink.rst

2. Same but use bigger pi

https://github.com/ArduPilot/ardupilot_wiki/blob/master/dev/source/docs/raspberry-pi-via-mavlink.rst

3. Video tutorial for item no 2.

https://youtu.be/cZVNndOaYCE

4. Pixhawk and arduino

https://discuss.ardupilot.org/t/mavlink-and-arduino-step-by-step/25566