CAN Bus Interface
CAN bus is a communication interface that lets multiple electronic units exchange messages over a two-wire, differentially signalled line. Messages carry an identifier instead of an address; of two nodes talking at the same time, the one with the lower identifier wins the line and completes its message undisturbed.
The reason it is widespread in vehicle and construction machinery electronics is that it offers a structure that is robust in a noisy environment and saves cabling.
- Physical layer: a twisted pair of wires, CAN_H and CAN_L. A 120 ohm termination resistor is usually placed at both ends of the line; when termination is missing or excessive, the error counter increases.
- Speed and distance: common speeds are 125 kbit/s, 250 kbit/s and 500 kbit/s. As the speed rises the permitted line length shortens; in classic CAN, 1 Mbit/s is typically limited to a few tens of metres.
- Error management: every node keeps an error counter; a node that continuously produces errors takes itself off the line and does not lock up the network.
A board being CAN-capable does not mean it is automatically compatible with the vehicle it will be connected to: the message content and identifier layout are specific to the vehicle manufacturer. For this reason, a request to connect to a vehicle over CAN is a topic that must be evaluated separately at the start of the project.
The context in which this term is used: Our Services