Code to handle a lot of switches on an arduino.

Each pin declared in main.cpp:pinData should be receiving data from 2 daisy 
chained 74HC165 shift registers.

If a pin is declared and not wired to shift registers, it should be grounded.

Latches all wired to pin 10.
Clocks all wired to pin 11.

Data are sent through the serial port as [AAAABBBB...] where A is the 2 bytes 
received on pin 2, B the 2 bytes received on pin 3, etc.

You can debug by connecting another Arduino on port 12 and 13 with that code:
https://github.com/fgaudin/ArduinoDebugger

This can handle up to 128 switches.

References:
- http://www.martyncurrey.com/arduino-serial-part-1/
- http://www.martyncurrey.com/arduino-serial-part-2-serial-data/