The Sparkle HAT connects to Raspberry Pi GPIOs, does 3.3V->5V level shifting to connect to HUB75 LED matrixes (to be controlled with the rpi-rgb-matrix code), and the Sparkleswitch-specific IDC-12 connector to connect to the switch box.
The level shifters are needed as the LED matrixes need 5V logic level. We also use two free drivers to provide 5V TTL level for the trigger relay outputs on the IDC-12 connector.
Inputs (from switches and sense-lines all operating at 12V) are insulated with PC817 opto couplers. The relay trigger outputs are non-insulated as the receiving end uses opto-couplers already.
To provide strong mechanical support, the HAT is full size with all four mounting holes.
