Transforming your AVR Microcontroller to the I2C or TWI Slave I/O Expander Project

The I2C bus (read as I squared C) is one of the most important embedded system serial bus interface first introduced by Philips in 1980; using just two lines called SCL (serial clock) and SDA (serial data) respectively make the I2C bus is a perfect choice to provide additional I/O capabilities to your microcontroller project without changing your microcontroller type and design in order to increase the I/O port pins. You could read more information at ermicroblog