Research Of CAN Bus Communication Control System Based On Multiple Logical Links

With the rapid development of computer technology in our country and the continuous improvement of automobile electrical technology,more and more application technologies are realized in the automobile.In the meantime,the growing abundance of automotive features has also driven the car's electronic control unit to become more sophisticated.As the "brain" of automobiles,automotive electronic control units control the normal operation of the various systems of automobiles through the adjustment of parameters,electronic control units also fundamentally affect the safety and stability of the car.and the current development trend of automotive electronic control units is also more intelligent.Therefore,at present,Obtaining the current status of each part of the automobile by communicating with the ECU of the automobile is a very important step in the work of diagnosing the vehicle.However,because the electronic control unit on the car is very complicated and the number of ECU is increasing,it generally reflects that the diagnosis and detection of the electronic control unit of the automobile takes too long.Therefore,improving the efficiency of communication with ECU is a problem that needs to be solved urgently.This thesis is based on the deep research of ISO15765-2 network layer protocol and CAN bus protocol which are used in the communication between testing equipment and automotive ECU.This paper realizes a communication control system based on multiple logical links.The main purpose is to change the characteristics of the serial communication between the original detection equipment and the automobile electronic control unit,so that the communication control system can communicate with the automobile ECU concurrently,the efficiency of ECU testing and assembly in the actual production line can be improved.The main work of this paper is as follows:First,the key technologies of communication control system and ECU communication are discussed deeply,including the CAN bus and ISO15765 protocol in detail.The key point is to study and analyze the ISO15765-2 protocol.The single frame,the first frame,the continuous frame and the flow control frame in the protocol are all discussed in detail,and some possible errors such as overtime and unexpected frames and Its solution are described.Second,the overall structure of the communication control system is introduced briefly.The hardware resources and software design of the system are introduced.In the communication between the upper diagnosis system and the communication control system,a set of communication protocol is defined to solve the problem like sticky packets,packet breaking problems in TCP communication.In communication between the communication control system and the electronic control unit of the automobile,the ISO15765-2 protocol is realized,on the basis of this protocol,the idea of multiple logical links is proposed,and the workflow of the multiple logical links at the sending and receiving ends is introduced in detail.Third,the system was realized by AM3354 development board,and the system was tested on the actual production line.The test message was written into the test log,and a detailed analysis of the message is carried out to draw the conclusion of the test.The test results show that the communication control system can not only complete the detection of automotive electronic control,but also effectively improve the detection efficiency in the production line.This proves the feasibility of the communication control system based on multiple logical links.