CAN Bus: Advantages and Disadvantages

This article explores the pros and cons of using a CAN (Controller Area Network) bus, comparing it to other bus interface options.

Introduction:

• CAN stands for Controller Area Network.
• It was developed by Robert Bosch initially for in-vehicle networking in automobiles.
• It’s a differential, two-wire interface.
• It’s a multi-drop, multi-master serial bus protocol.
• It’s used for communication between controllers, actuators, and sensors.
• It uses a single twisted pair wire, terminated at each end, with nodes connected to it.

Advantages of CAN Bus

Here are the advantages of using a CAN bus compared to other bus types:

• High Data Rate: It allows for data rates up to 1 Mbps. The CAN FD (flexible data rate) version supports even higher speeds, exceeding 2 Mbps.
• Increased Bandwidth (CAN FD): CAN FD offers significantly more bandwidth, potentially eight times that of a standard CAN bus.
• Reduced Wiring: It minimizes wiring complexity in automotive applications, leading to simpler and more efficient systems.
• Wide Industrial Use: Due to its less complex interface, it’s commonly used across various industries, not just automotive.
• Cost and Time Savings: It saves overall cost and time through reduced and simplified wiring and the use of flash programming.
• Data Field Size: Standard CAN protocol supports 8 bytes in the data field, while CAN FD supports 64 bytes.
• Automatic Retransmission: It automatically retransmits lost messages, enhancing reliability.
• Robustness: It functions reliably in diverse electrical environments without major issues.
• Error Detection: The protocol incorporates different error detection mechanisms, including bit errors, acknowledgment errors, form errors, CRC errors, and stuff errors.

Disadvantages of CAN Bus

Here are the disadvantages of CAN bus compared to other bus types:

• Node Limit: Although the maximum number of nodes is not explicitly defined, electrical loading limits the practical number of nodes to around 64.
• Distance Limitation: It supports a maximum length of about 40 meters for the bus.
• Potential Interactions: There is a possibility of undesirable interactions between nodes.
• Software Costs: It can involve higher costs for software development and maintenance.
• Driver Requirements: The CAN driver must produce at least 1.5V across a typical 60 Ohm impedance.
• Topology Restrictions: The network should be wired in a topology that minimizes stubs to avoid signal reflections.
• Termination Required: To minimize signal integrity issues like reflections, the CAN bus should be properly terminated at both ends with resistors.
• Node Removal: Removing a node requires the use of appropriate 120 Ohm termination resistors at the relevant points on the CAN bus.