I2C Foundations

~10 min slides

What is I2C?

I2C (or IIC) stands for Inter-Integrated Circuit. It is a two-wire bus protocol for communicating with sensors, displays, and other devices.

The two wires are:

• SDA — Serial Data (bidirectional). Used to propagate data bits.
• SCL — Serial Clock (driven by the controller). Used to propagate a clock to synchronize data exchanges on the bus.

Since it is a bus, multiple devices can share the same two wires. Each device has a unique address (7-bit) that the controller (master) can use to address any other device (slave) on the same bus.

Theory of Operation

• Each bus has at least one master and one or more slaves that it communicates with. The master is the entity that orchestrates operations on the bus.
• Typically, the microcontroller we are programming would be the master. The master addresses the slaves using the 7-bit address.
• The exchange speed of the data is governed by the clock speed (propagated on the SCL line).
• A master can perform two operations: either read or write.
• I2C exchanges data in one-byte chunks.

Write Operations

A master writes data to a slave. You need to provide:

• The address of the slave
• An array of bytes that need to be written

Read Operations

A master reads data from a slave. You need to provide:

• The address of the slave
• A byte array buffer for the received data

Configurations