Controller Area Network (CAN) – Complete Guide

 What is CAN?

Controller Area Network (CAN) is a serial communication protocol developed for real-time and reliable data exchange between multiple electronic control units (ECUs) without using a host computer.
It is widely used in automobiles, industrial automation, medical devices, and embedded systems because of its high speed, robustness, and error detection capability.

It was developed by Robert Bosch in 1986 for automotive applications.

Why CAN is Used?

Traditional communication methods required complex wiring between devices.
CAN solves this by using:

✔ Two-wire communication system
✔ High noise immunity
✔ Multi-master communication
✔ Real-time data transfer

How CAN Works

1. All nodes are connected using a twisted pair cable (CAN High & CAN Low).

2. Each node can send and receive messages.

3. Messages are broadcast to the entire network.

4. Every node checks the message identifier and decides whether to accept or ignore it.

5. Priority-based arbitration ensures that high-priority data is transmitted first.

Main Components of CAN

1. ECU (Electronic Control Unit)

The device that sends and receives data.

2. CAN Controller

Converts parallel data into serial data and vice versa.

3. CAN Transceiver

Converts logic signals into differential signals for transmission.

4. Bus (CAN High & CAN Low)

The communication medium.

5. Terminator

A 120Ω resistor placed at both ends to avoid signal reflection.

CAN Frame Format

1. Data Frame

Carries actual data.

2. Remote Frame

Requests data from another node.

3. Error Frame

Detects transmission errors.

4. Overload Frame

Adds delay between frames.

Types of CAN

1. Standard CAN

Uses 11-bit identifier.

2. Extended CAN

Uses 29-bit identifier.

CAN Bus Speeds

• Low-speed CAN → Up to 125 kbps

• High-speed CAN → Up to 1 Mbps

• CAN FD → Up to 8 Mbps

Applications of CAN

Automotive

• Engine control unit

• Airbag system

• ABS

• Power steering

• Infotainment system

Industrial Automation

• PLC communication

• Robotics

Medical Equipment

• Patient monitoring systems

Aerospace

• Aircraft communication systems

Advantages of CAN

✅ Reduced wiring
✅ High reliability
✅ Excellent error detection
✅ Priority-based communication
✅ Multi-master support
✅ Cost-effective

Disadvantages of CAN

❌ limited data length (8 bytes in classical CAN)
❌ Speed decreases with long distance
❌ Complex message configuration

CAN in Embedded Systems

CAN is widely used in real-time embedded systems because it provides:
✔ Deterministic communication
✔ Low latency
✔ High fault tolerance
✔ Efficient multi-device connectivity

Microcontrollers like ARM, PIC, and AVR have built-in CAN controllers.

Future Scope of CAN

• CAN FD for faster communication
• CAN in electric vehicles (EVs)
• Integration with IoT and Industry 4.0
• Advanced driver assistance systems (ADAS)
• Autonomous vehicles

Conclusion

The Controller Area Network (CAN) is a powerful, reliable, and efficient communication protocol that plays a vital role in modern vehicles and industrial embedded systems.
With the evolution of CAN FD and smart automotive technologies, it will continue to be a key communication backbone for future intelligent systems.