Centipede didn't work for me. What am i doing wrong?
My wiring
the twisted pair (white and orange) are the SDA and SCL lines. First I had SDA pin 13 going to arduino pin 5 and SCL pin 12 going to arduino pin 4. Then I placed a 10K resistor in the middle of each of those wires and connected them to +5V along with pin 18. The resistors on the mcp23017's i/o and LED are 330ohm. I'm note sure if that's right but that what I could gleam from this schematic.
found here : Tutorial: Maximising your Arduino’s I/O ports with MCP23017 | tronixstuff.com