The Inter-integrated Circuit (I2C)

I2C is ordinarily pronounced “I-two-C”, though it is also sometimes written as IIC (and pronounced “I-I-C”) or I2C (pronounced “I-squared-C”). The acronym stands for Inter-Integrated-Circuit. It is a type of serial computer bus and communications protocol that was first introduced to the market by Philips Semiconductor in 1982.

I2C is a way of allowing multiple electronic devices (most often low-speed, peripheral integrated circuits) to communicate with each other over a single pair of wires. These wires are also called data lines, or buses. The first of these buses is the data line and is called the SDA (Serial DAta) line, and the other bus is the clock, or SCL (Serial CLock) line. Since all devices on any I2C circuit are hooked to these two lines to communicate, most I2C-compatible devices have pins labeled SDA and SCL, as well as VIN and GND pins for positive and ground connections.

I2C uses two wires to connect multiple devices in a multidrop bus. The bus is bidirectional, low-speed, and synchronous to a common clock. Devices may be attached or detached from the I2C bus without affecting other devices. The data rate of I2C is somewhat slower than SPI, at 100kbps in standard mode and 400kbps in fast mode.