An add-on board for the raspberry Pi featuring the Microchip MCP23017 IO controller Easy to assemble kit offers similar features found on the Gert board 16 inputoutput lines driven off the external chip This device offers protection to the Pi & can drive more power per pin Same size as the Slice of Pi board Boards can be daisy chained to give up to 128 ports The device supports 4 wire daisy chain connector PWRGNDSCLSDA breakout for Interrupt A & B daisy chain up to 8 for 128 IO pins Supplied with 2 x 8 way 0.1 pitch layout for of all 16 IOs & 2 x 8 way 0.1 pitch common ground for ease of use 0.1uf decoupling capacitor IC & IC holder