1. CAN (Controller Area Network) bus has high performance and reliability, and is mainly used for communication between two devices, and is widely used in industrial automation, ships, medical equipment, industrial equipment, etc. Fieldbus is one of the hotspots in the development of technology in the field of automation today, and is known as the computer local area network in the field of automation. Its appearance provides a strong technical support for the distributed control system to realize real-time and reliable data communication between nodes.
2. The CAN controller judges the bus level according to the potential difference between the two lines. Bus level is divided into dominant level and recessive level, the two must be one of them. The sender sends a message to the receiver by changing the bus level.
3. CAN communication soldiers do not synchronize with clock signals, it is a kind of asynchronous communication , and only has two signal lines, which together form a set of differential signal lines , and communicate in the form of differential signals.CAN_HighCAN_Low
4. CANMultiple communication nodes can be mounted on the bus, and the signals between nodes are transmitted through the bus to realize communication between nodes. Since the CAN communication protocol does not encode the address of the node, but encodes the data content , the number of nodes in the network is theoretically unlimited, as long as the load of the bus is sufficient, the load can be increased through the repeater.
5. The physical layer of the CAN bus protocol has only one pair of differential lines, which can only represent one signal at a time. Therefore, for communication nodes, CAN communication is half-duplex , and sending and receiving data needs to be carried out in time-sharing . In the CAN communication network, because of the shared bus, only one communication node can send signals at the same time in the entire network, and the rest of the nodes can only receive signals at that time.
6. Frame introduction (CAN communication is carried out with 5 types of frames):
data frame: used for communication nodes to transmit data to the outside.
Remote control frame: used to request data from remote nodes.
Error frame: used to notify the remote node of a verification error and request to resend the previous data.
Overload frame: used to notify the remote node: this node is not ready to receive.
Interval frame: A frame used to separate data frames and remote control frames from previous frames.