I picked up one of these 4x4 Independent Keyboard Matrix modules to see how useful it might be for arbitrary input with a microcontroller.
I examine how it is constructed, and provide some examples of how to make it work:
LedControl - controlling the LEDs;
KeyMatrixInput - multiplexed key input;
SwitchInterrupts - interrupt-driven switch input.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
