Controller Area Network or CAN or CAN-Bus is a broadcast based, multimaster, mailbox base, serial bus standard used in automobiles since the 1980s and refined into industry standards in the 1990s. It allows multiple electronic control units (ECUs) to communicate to accomplish a given task.
CAN supports both vehicle control and industrial control. In an industrial control setting it may be referred to as a fieldbus. The predominate applications are automotive.
A CAN bus may have multiple ECUs on the network, and typically these ECUs are grouped into sensors, actuators and controllers. The sensors measure various settings – fuel mixture for example, actuators change settings of various elements – amount of fuel or air being supplied, and controllers either route messages or co-ordinate message processing.
Each ECU may be either a master or a slave and a sensor, actuator or controller. Each ECU internally consists of an MCU, CAN controller hardware, a transceiver, and for sensors, one or more sensors. Actuators have one or more actuators. Controllers are by definition masters on at least one CAN bus.
The maximum CAN data rate is 1MBPS at less than 40m which decreases to 125KBPS at .5Km.
In a gasoline or diesel fueled vehicle, the main ECU is an engine control unit. It is a controller that interacts with various sensors (e.g. fuel per cylinder), actuators (e.g. fuel on/off per cylinder) and other controllers to maximize engine performance. Other ECU sets control the transmission, ABS, infotainment, instrumentation, locks, windows, seat belts, lights and more.
Unison and DSPnano both support CAN on an on demand basis for a given processor. MCU vendors offer a basic library. RoweBots augments this basic library with a POSIX/Linux compatible interface based on standard message queues to both send and receive CAN messages.
The CAN data link layer protocol is standardized in ISO 11898-1 (2003). This standard describes mainly the data link layer — composed of the logical link control (LLC) sublayer and the media access control (MAC) sublayer — and some aspects of the physical layer of the OSI reference model.
In industrial settings, CAN is being augmented by CANopen at higher layers. In the automotive sector, the entire automobile environment is being converted to Autosar, a more comprehensive software standard.
Contact us to try CAN with Unison or DSPnano.
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