Development status and prospect of CAN bus
To promote the development of CAN and the CAN protocol, CiA(CAN in Automation) was established in Europe in 1992. Under the efforts of CiA, CAN technology has been widely used in automobile electronic control system, elevator control system, security monitoring system, medical instrument, textile machinery, ship transportation and so on. More than 400 companies have joined the CiA and the agency has become the global authority on the application of CAN technology.
The advantages of CAN bus in networking and communication functions as well as its high performance and price ratio determine that it has broad application prospects and development potential in many fields. The system of large instruments and equipment is complex, which can collect, process, control and output a variety of information. Such as medical device CT tomography scanner, in order to ensure its reliable work, the data communication requirements can be freely exchanged between functional blocks, communication can be broadcast, simple and economical hardware interface, communication line as little as possible, strong anti-interference ability, high reliability and automatic fault identification and automatic recovery. However, these requirements have not been well solved for a long time until the emergence of CAN bus technology provides a better solution. Measurement and control system can not be separated from the sensor, due to the different working principles of various sensors, the final output of the form of electricity is also different, in order to facilitate the system connection, usually consider the output of the sensor into a standard voltage or current signal. Even so, A/D link must be added when connecting to the computer. If the sensor can be output in digital form, it can be easily connected to the computer directly, thus simplifying the system structure and improving the accuracy. The bus connecting the sensor to the computer can be called the sensor bus.
In fact, the sensor bus still belongs to the field bus, the key problem is how to integrate the bus interface with the sensor. In a wide range of industrial control fields, CAN bus can be used as a field bus at the field equipment level, and compared with other buses, it has high reliability and cost-effective. This will be the main direction of CAN technology development and application. In the past domestic measurement and control field, because there is no better choice, most of them use BITBUS or RS-485 as the communication bus. Its main shortcomings are: one master more than the slave, no redundancy; Data communication is command response with low transmission rate. Poor error handling ability. The above problems CAN be solved by using CAN bus technology. Any node in CAN network can act as the master node to exchange data with other nodes actively. The information frames of CAN network nodes can be prioritized, which is convenient for real-time control. The physical layer and data link layer of CAN have unique design technology, which greatly improves its performance in anti-jamming and error detection. The above characteristics of CAN make it one of the preferred fieldbuses in many industrial measurement and control fields.
According to domestic and foreign data reports, CAN technology has been applied to household appliances and intelligent buildings and residential construction. Such as security system, meter reading system, home appliance control, etc. It has little investment, every node can be accessed randomly, the communication speed fully meets the requirements, and the data exchange volume in this kind of application is very small. Appropriate gateway such as CAN and TCP/IP protocol conversion, CAN make a room or a building of on-site CAN information into the form of the Internet, or in turn through such a gateway to the external network information into the form of CAN, which is to achieve the so-called remote control.