This is a library for the MCP23008 I2c Port Expander. These chips use I2C to communicate, 2 pins required to interface. Adafruit invests time and resources providing this open source code, please support Adafruit and open-source hardware by purchasing products from Adafruit! Ported to MCP23008 I2c Port Expander by Florian Kapust src-one.com Based on MCP23017 source of Limor Fried/Ladyada for Adafruit Industries. BSD license, check license.txt for more information All text above must be included in any redistribution To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder MCP23008. Check that the MCP23008 folder contains MCP23008.cpp and MCP23008.h Place the MCP23008 library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.