Heliowatcher

https://github.com/sciguy14/HelioWatcher/tree/master/Code/HelioWatcher single char puts between two devices over serial

serial
https://github.com/sciguy14/HelioWatcher/blob/master/Code/HelioWatcher/HelioWatcher.c https://github.com/sciguy14/Arduino-Tutorial-Series/tree/master/06%20Serial%20Comm%20and%20Processing

links
State machine