//DIGITAL_READ(2, A4, 4); //Not avaliable on Arduino Uno, i2c pin. //DIGITAL_READ(2, A5, 8); //Not avaliable on Arduino Uno, i2c pin.

Arduino library for I2C MCP23017 16 channel port expander - quiknick/MCP23017_NK ...

A while ago I received a couple of I/O port expander modules that use the I 2 C protocol. Using that Chinese module, you can use only the SDA and SCL pins of your ...