Communication between microcontrollers and different peripheral devices require some sort of digital protocol. I²C is a common communication protocol that is used in a variety of devices from many different product families produced by TI. This application note begins with a basic overview of the I²C protocol, describing the history of the protocol, different I²C speed modes, the physical layer of the digital communication, and the structure of the data. Several examples of the communication protocol are shown with different data converters. Finally, this application note covers some uncommon aspects of the protocol, including reserved addresses, clock arbitration and stretching, electrical timing and voltage specifications, and pullup resistor calculation.