Each tile has a different patch on the application side.
Adafruit TCS34725 color sensors reside underneath each tile to sense which type of tile is where. The sensors are wired up to an arduino ethernet which communicates with a
Raspberry Pi to process the data.
InGrid is equipped with a
Raspberry Pi which controls the arduino and keeps track of the state of the table. When an iPad is placed into the table, it communicates with the Raspberry Pi to get information about the state of the table. You can open up a view of the table on the iPad at any time to view the current table configuration when tiles are flipped down.