I am creating an arduino checkerboard(board game) that is hooked up to an 8x8 led matrix that has a live feed of the checkers location. I decided on placing reed switches under every single square of a checkerboard (64) and attaching magnets to the base of checker pieces.

Theoretically, this could work... But, how in the world do I wire 64 reed switches and an 8x8 led matrix all to one arduino?

What inputs and outputs do I even use?

 

Please post a schematic of what you have so far, the solution can be 'worked into' your current design.

 

You could use a 4 of these without any matrixing....
http://www.learningaboutelectronics.com/Articles/MCP23017-IO-port-expander-circuit-with-arduino.php
There are ways of using a keyboard matrix to save port pins.
https://playground.arduino.cc/Main/KeypadTutorial
One 16bit port expander would give you plenty of pins in a matrix.
And only use 2 Arduino pins

 

If you put the switches in a matrix to save input/output pins then you will have to add diodes -- one for each switch. This is because more than two switches can be on at a time and this causes "sneak" paths without the diodes.

Here is a good explanation:
http://blog.komar.be/how-to-make-a-keyboard-the-matrix/

 

How will the board determine red, black, and king?

ak

 

How will the board determine red, black, and king?

ak

That was my first thought too!

 

If you control the polarity of the magnets, such that (for example) north is up for all red pieces and down for all black pieces, and replace the reed switches with Hall Effect sensors, then you can electronically detect red, black, red king, and black king.

ak

 

That is a good idea to use Hall sensors to determine the red/black info, as long as the hall sensors are analog. Then you will also need an analog MUX to select the inputs, but that is pretty easy.

 

You know the initial configuation, and each move, which is enough to determine the new state.

Bob

 

You know the initial configuation, and each move, which is enough to determine the new state.

And you could use color/bi-color LEDs and brightness to differentiate between black/red and kings.