The CAN bus protocol is one of several approaches to solving a very basic problem — how can several electronic components scattered around a mechanical system share information?

Before protocols like CAN bus were developed, if you had a series of electronic components that needed to pass information amongst themselves, you had to set up a point-to-point network with a lot of wiring. Every device needed a connection to every other device if you wanted them to communicate.

This style of communication takes a lot of wiring, and it's not very flexible. If you wanted to add another node on the network, it's a big project!

Here's a point-to-point network with only 6 nodes. As you can see, tracing the wiring is daunting.

Less wiring is nice.

There have been a lot of innovations in network communications since. Use of a host controller, for example, simplified wiring dramatically, but it introduced the complication of a host controller just to manage communications along the network.

CAN bus was developed by Bosch, and in 1991, the protocol was used in a production vehicle for the first time.

CAN bus uses minimal wiring, but does not require a host controller. Today, you'll still find CAN bus networks in vehicles, but they are also used in plant environments, assembly lines, medical machinery, and even in prosthetic limb automation!

CAN Bus allows various electronic components to communicate on a single or dual-wire network data bus up to a speed of 1 Mb/s.

CAN bus allows the nodes to communicate without complex wiring or a host controller.

A bus inside of a bus, using the CAN bus protocol for communication.

CAN bus is the name of the message-based communication protocol, but it can also refer to the physical bus used in the CAN network.

To try to avoid confusion, in this lesson we will refer to the protocol as "CAN bus", and the physical cable simply as the "bus." Together, all of the physical components — the bus and the nodes — make up the CAN bus network.

We won't mention the city bus again.

Engine Management
Electronic Control
Unit

Transmission
Electronic
Control
Unit

Connector

Terminal Resistor

Bus

Terminal Resistor

Branch
Line

Branch
Line

Branch
Line

Branch
Line

Anti-Lock
Braking
Electronic
Control
Unit

Power Steering
Electronic
Control
Unit

Here's a sample CAN bus network, showing 4 ECMs connected via branch lines to the bus.

Building a Network

Multiple types of components may be used with CAN bus, provided they are CAN-capable, including:

• Electronic Control Units (ECM)
• Microcontrollers
• Sensors
• Actuators
• Gateways (or bridges) to interface with other networks