networks//network protocols//CAN

**Controller Area Network** is a shared bus where intelligent nodes exchange messages identified by a **CAN ID**, born to connect the electronic controllers of a vehicle. Intelligence is already distributed in the nodes; there is no master reading everyone.

Controller Area Network is a shared bus where intelligent nodes exchange messages identified by a CAN ID, born to connect the electronic controllers of a vehicle. Intelligence is already distributed in the nodes; there is no master reading everyone.

A node publishes a frame with an identifier; every node on the bus sees it and the interested ones read it. Conceptually close to publish-subscribe, although CAN is not MQTT: there is no broker, the bus itself is the medium, and the identifier doubles as the priority.

Physically it is a differential pair, CAN High and CAN Low, terminated at both ends, robust against noise. Collisions are resolved by arbitration on the identifier bits, which gives efficient real-time behavior for embedded systems. J1939 is the higher-level protocol used on top of it in heavy vehicles and machinery.

Against a request-response fieldbus: in Modbus a PLC reads devices one by one; in CAN multiple controllers share messages on the bus. CAN is the natural fit for distributed systems with many peer nodes (Modbus).