Hardware

Idea for each matrix cell under chessboard

Small stripboard to be fixed under each space under the chessboard, with a wiring harness to go between each board to build the matrix.  

Breadboard layout for testing of leds and reed switch matrix

Yes, breadboards can get messy!

The real breadboard

The development circuit is a 3 x 3 matrix of 9 LEDs and 9 reed switches.  This should be ok for testing the basic code to read the reed switches and light LEDs as needed.  I'm not sure that it would be possible to get all 64 LEDs and switches on this size of breadboard :-).

The development matrix circuit diagram

This is an easier to follow of the circuit used in development.  I have used schottky diodes to prevent key ghosting, and 330ohm resistors for the LEDs.  Not all 64 LEDs will be on at the same time, as the current draw on the MCP23017 and Pi could be too much.