Flash the Arduino Mega 2560
For the inputs to handle we use an Arduino Mega 2560 which has a microcontroller. The controller is running a simple C++ program you can find in the GitHub Repository, readily available to be flashed.
You can either use Arduino IDE to do so. Just open the sketch, choose the right board type and port and then upload it to the Arduino.
Another possibility would be to use something like an Arduino-Makefile to transfer the ino sketch to a hex file and then flash it using avrdude.
For simplicity I suggest using Arduino IDE as it runs on all major Operating Systems.