CAN field bus magic - Solutions - Huaqiang Electronic Network

RF cable can be customized for other specifications

Photocoupler

Fieldbus is one of the hotspots in the development of technology in the field of automation today, and is known as the computer LAN in the field of automation. Its emergence provides powerful technical support for distributed control systems to achieve real-time and reliable data communication between nodes. CAN (ControllerAreaNetwork) belongs to the field bus field, which is a serial communication network that effectively supports distributed control or real-time control. Compared with many current RS-485 distributed control systems based on R-line construction, the distributed control system based on it has obvious advantages in the following aspects:

First, the CAN controller works in a multi-master mode, and each node in the network can compete to send data to the bus according to the bus access priority (depending on the message identifier) ​​using a lossless structure of bit-by-bit arbitration, and the CAN protocol is abolished. The station address code is used instead, and the communication data is encoded, which enables different nodes to receive the same data at the same time. These characteristics make the data communication between the nodes of the network formed by the CAN bus real-time and easy to construct. Redundant structure to improve system reliability and system flexibility. The use of RS-485 can only constitute a master-slave structure system, and the communication method can only be carried out in the manner of polling by the primary station, and the real-time performance and reliability of the system are poor;

Secondly, the CAN bus is connected to the physical bus through the two output terminals CANH and CANL of the CAN controller interface chip 82C250, and the state of the CANH terminal can only be a high level or a floating state, and the CANL terminal can only be a low level or a floating state. This guarantees that there will be no phenomenon in the RS-485 network. When the system has an error and multiple nodes send data to the bus at the same time, the bus is short-circuited, which may damage some nodes. Moreover, the CAN node has an automatic shutdown output function in case of a serious error, so that the operation of other nodes on the bus is not affected, thereby ensuring that there is no problem in the network, and the bus is in a "deadlock" due to a problem with an individual node. status.

Moreover, the perfect communication protocol of CAN can be realized by the CAN controller chip and its interface chip, which greatly reduces the difficulty of system development and shortens the development cycle. These are unmatched by only the RS-485 of the electrical protocol. In addition, compared with other fieldbuses, the CAN bus is a fieldbus that has formed international standards with many features such as high communication speed, easy implementation, and high cost performance. These are also important reasons why CAN bus is used in many fields and has strong market competitiveness.

CAN (Controller Area Network) is the controller area network, which belongs to the category of industrial field bus. Compared with the general communication bus, CAN bus data communication has outstanding reliability, real-time and flexibility. Due to its good performance and unique design, the CAN bus has received more and more attention. It is the most widely used in the automotive field, and some of the world's leading car manufacturers, such as BENZ, BMW, PORSCHE, ROLLS-ROYCE and JAGUAR (Americas) Leopards and the like use the CAN bus to realize data communication between the internal control system of the vehicle and each detection and execution mechanism. At the same time, due to the characteristics of the CAN bus itself, its application range is no longer limited to the automotive industry, but to the automatic control, aerospace, marine, process industry, machinery industry, textile machinery, agricultural machinery, robots, CNC machine tools, medical equipment. And the development of sensors and other fields. CAN has become an international standard and has been recognized as one of several of the most promising fieldbuses. Typical application protocols are: SAEJ1939/ISO11783, CANOpen, CANaerospace, DeviceNet, NMEA2000, etc.