RunLengthGPIO

This sketch makes the Arduino work as a GPIO interface for a computer, where input and output changes are transmitted in run-length encoding. Every time an input pin changes, the Arduino sends the new values of the input pins and the time since the last change. In a similar way, the Arduino can be programmed a sequence of output pin changes, each specified by the new values of the output pins and the time since the previous change.

Three application programs are included: the first makes two digital pins act as a TTL-levels UART; the seconds turns the value of the input pins into an image; the third reads codes from infrared remotes with a photodiode and a resistor connected to one of the input pins.