I2C

I2C or Inter-IC (integrated circuit) bus

• Introduction to I2C Protocol
• How I2C Communication works?
• Characteristics Of The I2C-Bus
• I2C project
• Advantages of I2C

Introduction to I2C Protocol:

Name I²C is shorthand for a standard Inter-IC (integrated circuit) bus.

Philips developed I²C for communication between devices inside for its TV / radio set. Examples of simple I²C-compatible devices found in embedded systems include EEPROMs, thermal sensors, and real-time clocks.

The main objective behind the invention of I2C bus is to establish a simple low pin count bus that can connect different ICs on a circuit board of Television or Radio. Later I2C grew beyond the limits of TV and Radio and now it can be found in almost every computer motherboards and other embedded devices. I2C can also be used for communication between multiple circuit boards in equipments with or without using a shielded cable depending on the distance and speed of data transfer.

Standard I²C devices operate up to 100Kbps, while fast-mode devices operate at up to 400Kbps. A 1998 revision of the I²C specification (v. 2.0) added a high-speed mode running at up to 3.4Mbps. Most of the I²C devices available today support 400Kbps operation. Higher-speed operation may allow I²C to keep up with the rising demand for bandwidth in multimedia and other applications.

I²C is appropriate for interfacing to devices on a single board, and can be stretched across multiple boards inside a closed system, but not much further. An example is a host CPU on a main embedded board using I²C to communicate with user interface devices located on a separate front panel board. A second example is SDRAM DIMMs, which can feature an I²C EEPROM containing parameters needed to correctly configure a memory controller for that module.

I²C is a two-wire serial bus, as shown in Figure 1. There's no need for chip select or arbitration logic, making it cheap and simple to implement in hardware.

 Figure 1

The two I²C signals are serial data (SDA) and serial clock (SCL). Together, these signals make it possible to support serial transmission of 8-bit bytes of data-7-bit device addresses plus control bits-over the two-wire serial bus. The device that initiates a transaction on the I²C bus is termed the master. The master normally controls the clock signal. A device being addressed by the master is called a slave.

In a bind, an I²C slave can hold off the master in the middle of a transaction using what's called clock stretching (the slave keeps SCL pulled low until it's ready to continue). Most I²C slave devices don't use this feature, but every master should support it.

The I²C protocol supports multiple masters, but most system designs include only one. There may be one or more slaves on the bus. Both masters and slaves can receive and transmit data bytes.

Each I²C-compatible hardware slave device comes with a predefined device address, the lower bits of which may be configurable at the board level. The master transmits the device address of the intended slave at the beginning of every transaction. Each slave is responsible for monitoring the bus and responding only to its own address.

How I2C Communication works?