Basics of I2C Communication Protocol (A Simple Guide)
I2C (Inter-Integrated Circuit) is a popular communication protocol that allows multiple devices such as sensors and microcontrollers to talk to each other on a single circuit board. It was created by Philips in the 1980s and is great for simple, low-cost communication with minimal wiring. This guide will explain the basics of I2C, its main features, and how it works in an easy-to-understand way.
What is I2C?
I2C is a type of communication system that allows different electronic devices to communicate using only two wires: one for data (SDA) and one for clock signals (SCL). These two wires connect all the devices on the I2C bus. One device acts as the master, which controls the communication, while the others are slaves that respond to the master.
Each device on the bus has a unique address, so the master can send or receive data from any unique device without any confusion.
How I2C works
I2C communication protocol works by sending data in small chunks called frames. Here is a simple breakdown of the process:
Start state:
The master device initiates communication by pulling the data line (SDA) low while keeping the clock line (SCL) high. This signals to all devices on the bus that communication is about to begin.
Address:
The master sends the address of the target slave device on the SDA line. A slave device with a matching address will be accepted by pulling the SDA line low.
Data Transfer:
The master can now send or receive data from the slave device. Data is sent in 8-bit chunks, and after each chunk, the receiver sends an acknowledgment (ACK) to confirm that it has received the data.
Stop Condition:
Once the data is transferred, when the SCL line is high the master releases the SDA line and sends a stop signal. This tells all devices that communication has ended.
Main features of I2C
Only two wires:
I2C uses only two wires, SDA and SCL, making it easy to connect multiple devices with fewer cables.
Multiple Devices:
You can connect multiple devices (both master and slave) on the same I2C bus. Each device has its unique address.
Addressing modes:
I2C supports both 7-bit and 10-bit addresses, allowing 127 or 1024 devices to be connected to the bus.
Clock Speed:
I2C can operate at various speeds from 100 kHz (standard mode) to 3.4 MHz (high-speed mode) depending on the application.
Synchronized communication:
The clock line (SCL) ensures that data sent between devices stays in sync, so communication is reliable.
Acknowledgment (ACK) bit:
After sending each piece of data, the receiver sends an acknowledgment bit to confirm that it has received the data, which helps detect errors.
Types of I2C Communication
Master sending data:
The master device sends data to the slave device. For example, a microcontroller (master) can send configuration settings to a sensor (slave). Do you want to know the comparison between Microcontroller vs Microprocessor, you can visit the Discrete website.
Master receives data:
The master requests data from the slave device. For example, the microcontroller (master) can query the sensor for temperature readings.
Multiple Masters:
In some setups, there may be more than one master device on the same bus. If two masters try to communicate at the same time, I2C has a way of handling conflicts.
Common call:
The master can send commands to all devices at the same time using a unique address (0x00). This is useful for resetting or setting up all devices at once.
Advantages of I2C
Simplicity: With only two wires required for communication, I2C is easy to set up and reduces the number of connections required between devices.
Efficiency: I2C allows multiple devices to share the same bus, so you don’t need as many separate connections, making it perfect for small systems.
Flexibility: It works at different speeds and supports multiple devices, so it can be used for a wide range of applications, from simple sensors to more complex devices.
Error detection: The acknowledgment (ACK) bit ensures that data is sent and received correctly, making it easy to detect any communication errors.
Disadvantages of I2C
Speed limitations: I2C is slower than some other protocols such as SPI, which can transfer data much faster. I2C is better suited for slower, less demanding tasks.
Short distance: I2C is designed for communication within the same circuit board or a very short distance. It is not ideal for long-distance communication.
Limited devices: You can connect up to 127 devices using 7-bit addressing. For large systems, this may not be sufficient. The number of devices can also be limited by the electrical characteristics of the bus.
Bus contention: When there are multiple masters, contention can occur if two masters try to communicate at the same time. I2C has a way to resolve these conflicts, but it adds complexity.