Controller Area Network, also called CAN or CAN-bus, is a computer network protocol and bus standard designed specifically for automotive applications.

Unlike a traditional network such as USB or Ethernet, CAN does not send large blocks of data point-to-point from node A to node B under the supervision of a central bus master.

Basically CAN is a multi-master broadcast, differential serial bus standard for connecting electronic control units with each other.

CAN is ideally suited in applications requiring a high number of short messages in a short period of time with high reliability in rugged operating environments. Since CAN is message based and not address based, it is especially suited when data is needed by more than one location and system-wide data consistency is mandatory.

History

Development of the CAN-bus started originally in 1983 at Robert Bosch GmbH.[1] The protocol was officially released in 1986 at the SAE (Society of Automotive Engineers) congress in Detroit.

After the first CAN controller chips was produced by Intel and Philips and released to the market in 1987, it also become popular in other areas like trucks, trains, busses, airplanes,agriculture, construction, mining,marine vehicles,factory automation, house automation, vending machines and others.

Bosch published the CAN 2.0 specification in 1991.

Application domain

Typical applications of the CAN bus are currently the use in vehicles to connect engine control unit and transmission. Also it is used to connect the door locks, climate control, seat control, etc.

Due to its robustness, low cost and flexible applicability it is nowadays also widely used in other environments besides of automotive applications

Cost

CAN popularity is highly due to the the low cost of some CAN Controllers and processors as the relatively easy usage and robustness of the protocol for most applications. Its cost, performance, and upgradeability provide for tremendous flexibility in system design.

Transmission rate and cable length

The CAN bus was developed as a multi-master, message broadcast system that specifies a maximum signaling rate of 1M bit per second (bps).

Cable length and transmission rate relate to each other in an inverse relation, which will be explained in following chapters and is related to the physical attributes of the executed protocol transmission strategy .

The furthest distance is 10km when the CAN bus speed is 5KB/s brutto data rate. When the CAN bus distance is 40m,the maximum speed can be theoretically reached of 1MB/s brutto data rate.

Safety

CAN provides five mechanisms for detecting errors. The CAN bus error rate is less than 4.7x10-11

Fault confinement is also a major benefit of CAN. Faulty nodes are automatically dropped from the bus, which prevents any single node from bringing a network down, and assures that bandwidth is always available for critical message transmission. This error containment also allows nodes to be added to a bus while the system is in operation, otherwise known as hot-plugging.

In a CAN network many short messages like temperature or RPM are broadcast to the entire network, which allows for data consistency in every node of the system.

License

An official use of CAN requires that a fee for the CAN Protocol License is to be paid to Bosch who developed the protocol and hold patents.