[John’s] currently working on a rather fun PiNoir & Santa Catcher Challenge, and one of the main components is a PiFace Control and Display, which allows you to use a Raspberry Pi without a keyboard or mouse. Curious to see how this module worked, [John] decided to do a tear down and find out!
Using a de-soldering tool he removed the 16×2 LCD which obstructs most of the components on the panel, which revealed a 16 bit SPI port expander from Microchip MCP23S17. He continued to examine components and checked values using a multimeter to come up with the following circuit diagram:
