This tutorial shows how to use the MCP23017 with an 8051 chip (C8051F410 Silicon Labs) with I2C protocol. I was wondering how the adafruit I2C LCD (https://www.adafruit.com/product/772) worked with only 2 pins.  They use … Continue reading Expand your mind, and I/O ports! MCP23017 IO Port Expander! Presto, Expando!