CAN belongs to the category of industrial fieldbus. It is a serial communication network that effectively supports distributed control or real-time control. Compared with many RS485 distributed control systems based on R-line, the distributed control system based on CAN bus has obvious advantages in the following aspects.

Industrial computer PCs are mostly serial port interfaces, which involve long-distance data transmission in actual wiring. The communication distance of RS232 and RS485 is far from meeting the requirements. Ideally, it can be solved through optical fiber, but some environments can not provide optical fiber communication. Therefore, can bus communication is the best choice.

The control center needs to control multiple sub stations and exchange data with them. At this time, the scheme can convert the serial port RS232 or RS485 of each computer into can bus for long-distance communication; Each substation PC can be connected with a can232g or can485g ultra remote driver of Boshi electronics.

The CAN controller works in multi master mode, and each node in the network can access the priority according to the bus (depending on the message identifier) it competes to send data to the bus by bit arbitration with lossless structure, and the CAN protocol abolishes the station address coding and instead encodes the communication data, which can enable different nodes to receive the same data at the same time. These characteristics make the data communication between nodes in the network composed of CAN bus strong real-time and easy to form redundancy RS485 can only form a master-slave structure system, and the communication mode can only be carried out in the way of master station polling, so the real-time performance and reliability of the system are poor.

Advantages of CAN bus protocol:

1. It has the advantages of strong real-time performance, long transmission distance, strong anti electromagnetic interference ability and low cost;

2. Adopt two-wire serial communication mode, with strong error detection ability, and can work in high noise interference environment;

3. It has priority and cutting promotion functions. Multiple control modules are connected to can bus through CAN controller to form a multi host local network;

4. Have reliable error handling and error detection mechanism;

5. After the transmitted information is damaged, it can be automatically retransmitted;

6. The node has the function of automatically exiting the bus in case of serious error;