While the Arduino family of boards connect to your computer using a USB virtual serial port, the ATmega ones have an actual serial connection on-board.

You can read the state of a button using Arduino and a few lines of code. The actual state is shown in the Serial Monitor window as 0 or 1, 0 meaning the ...

His code is available for download from his site, and works perfectly in the Arduino IDE. The whole thing consists of some simple, easily ported code to implement a bare minimum bit-banged serial ...