Designing Embedded Hardware

Controller Area Network (CAN)

Through the late ’70s and ’80s, the complexity of automotive electronics had grown considerably, with engine management systems, ABS braking, active suspension, electronic transmissions, and automated lighting, air-conditioning, security, and central locking. These individual systems do not exist in isolation; each is part of an integrated whole. A considerable amount of information exchange is required, and therefore some means of system interconnection must be provided. The conventional method was for point-to-point wiring, providing discrete interconnection between each subsystem. This methodology was a natural evolution from the simple electrical systems of earlier cars, but as automotive complexity grew, such a scheme proved vastly inadequate. Each car could have several kilometers worth of wiring and dozens of connectors. Such complex wiring systems added greatly to the cost of producing a car, added unnecessary weight, reduced reliability, and made servicing a nightmare.

The obvious solution was to replace complexity with simplicity and implement intersystem communication using a low-cost digital network. The automotive electrical environment is very noisy. With electric motors, ignition systems, RF emissions, and so on, the 12V supply to automotive electronics can have ±400V transients. The required communication network must therefore be able to cope with this noise and work reliably. The network must provide high-noise immunity, as well ...