What is the CAN bus communication protocol?-EEWORLD

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CAN bus

CAN is the abbreviation of Controller Area Network
(hereinafter referred to as CAN), which is an ISO internationally standardized serial communication protocol. In the automotive industry, various electronic control systems have been developed to meet the requirements of safety, comfort, convenience, low power consumption, and low cost. Since the data types used for communication between these systems and the requirements for reliability are different, there are many cases where multiple buses are used, and the number of wiring harnesses increases accordingly.

In summary, when a node wants to send data to other nodes, the CPU of the node transmits the data to be sent and its own identifier to the CAN chip of the node and is in the ready state; when it receives the bus assignment, it switches to the message sending state. The CAN chip organizes the data into a certain message format according to the protocol and sends it out. At this time, other nodes on the network are in the receiving state. Each node in the receiving state detects the received message to determine whether these messages are sent to itself to determine whether to receive it.

CAN bus structure diagram CAN bus has many advantages: the communication rate can reach up to 1MB/s (the maximum distance is 40m at this time). The actual number of nodes can reach 110. It adopts a short frame structure, and the number of valid bytes in each frame is 8. Each frame of information has CRC check and other error detection measures, and the data error rate is extremely low. The communication medium can be twisted pair, coaxial cable and optical fiber. Generally, cheap twisted pair can be used without special requirements. In the case of serious errors, the node has the function of automatically shutting down the bus and cutting off its connection with the bus so that other operations on the bus are not affected.

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