Controller Area Network (CAN)
•Controller Area Network (CAN) is a fast serial bus that is designed to provide
–an efficient,
–Reliable and
–very economical link between sensors and actuators.
•CAN uses a twisted pair cable to communicate at speeds up to 1Mbit/s with up to 40 devices.
•Originally developed to simplify the wiring in automobiles.
•CAN fieldbuses are now used in machine and factory automation products as well.
CAN features
•Any node can access the bus when the bus is quiet
•Non-destructive bit-wise arbitration to allow 100% use of the bandwidth without loss of data
•Variable message priority based on 11-bit (or 29 bit) packet identifier
•Peer-to-peer and multi-cast reception
•Automatic error detection, signaling and retries
•Data packets 8 bytes long
CAN architecture
–an efficient,
–Reliable and
–very economical link between sensors and actuators.
•CAN uses a twisted pair cable to communicate at speeds up to 1Mbit/s with up to 40 devices.
•Originally developed to simplify the wiring in automobiles.
•CAN fieldbuses are now used in machine and factory automation products as well.
CAN features
•Any node can access the bus when the bus is quiet
•Non-destructive bit-wise arbitration to allow 100% use of the bandwidth without loss of data
•Variable message priority based on 11-bit (or 29 bit) packet identifier
•Peer-to-peer and multi-cast reception
•Automatic error detection, signaling and retries
•Data packets 8 bytes long
CAN architecture
Tradeoff: CAN bus versus point-to-point connections
By introducing one single bus as the only means of communication as opposed to the point-to-point network, we traded off the channel access simplicity for the circuit simplicty
Since two devices might want to transmit simultaneously, we need to have a MAC protocol to handle the situation.
CAN manages MAC issues by using a unique identifier for each of the outgoing messages
Identifier of a message represents its priority.
CAN: message format
By introducing one single bus as the only means of communication as opposed to the point-to-point network, we traded off the channel access simplicity for the circuit simplicty
Since two devices might want to transmit simultaneously, we need to have a MAC protocol to handle the situation.
CAN manages MAC issues by using a unique identifier for each of the outgoing messages
Identifier of a message represents its priority.
CAN: message format