How does the power work? Do I connect one through USB and the other through a power adaptor? Or do they both run off a shared connection (if not, do they have to have a common ground?).
Which data type is best for exchanging values from 0 to 255, DEC?
You can make them share power by connecting 5v and GND together.
Use BYTE to send the values. DEC is for humans only. 