| CAN(Controller Area Network) bus is a serial bus network that connect to electronic device and sensor within the same system or subsystem. Since the current competition in the automotive industry intensifies, consumer expectations of automotive's comfort, safety, and the car internal electronic systems is increasing. Therefore, a variety of electronic monitoring devices are used in automotive systems, but communications in these devices are different, it constitutes a variety of bus architectures, the number of wire harness have increased, resulting in vehicle wiring systems become more complex. Based on the characteristics of CAN bus communication, communicated between the units are on the same platform, the CAN bus as the "highway" of communication with these devices, so it is possible to significantly reduce the number of wiring harness; at the same time, CAN bus can easily to install the device, and can be adapted to various transmission media. Therefore, CAN bus is widely used in automotive vehicle systems.The CAN bus network diagnosis is a technology that used in each network node communication failure detection. With the continuous development in automotive electronics and computer technology, automotive vehicle electronic control unit in the system continues to increase, resulting a failure associated with the control unit is also constantly increasing. Once the communication system within the body of an electronic control unit fails, then they can quickly diagnose the network communication failures with the methods of network diagnosis and repairs it by updating the application.The paper intended to develop a system repair the failure without dismantling vehicle instrumentation, but need updated the applications by the way of diagnosis on line. Since the vehicle instrument without a network diagnostic function after loading the car, once a communication failure appeared, it need remove the automotive vehicle and return it to the instrument Factory detect and re-update to fix the problem, which will undoubtedly give customers a very large trouble; if the vehicle instrument with a network diagnostic function,it will not be required to remove the instrument, the body can diagnose failure in signal communication line and field updates instrumentation applications to troubleshoot problems. To this end, the present paper a study from the following:(1) The fundamentals and protocols of CAN bus communications.(2) The network diagnostics protocol about ISO-14229 and ISO-15765 and diagnostic services.(3) The method of writing data to the Flash and EEPROM based on standard network diagnostic. Combined with the actual project to optimize speed of writing data.(4) Analyze the reasons for writing Flash or EEPROM data failure during communication via the network diagnostic services record.(5) Researched on how to ensure that data downloaded into the Flash or EEPROM is correct.In this paper, with understanding of CAN communication protocol and network diagnostic protocol, developing platform system tool with the Visual Studio 2013 tool, packing the diagnostic services data frame which are send to the meter ECU(Electronic Control Unit) by the tool, in accordance with the diagnostic protocol to unpack and analyze diagnostic information that ECU returned to complete the corresponding service functions. Therefore, this paper developed by the automobile instrument data to update the system by simply connecting the car dashboard CAN packets and tools, load the update file which contains the package data and packed into a standard format diagnostic services realize data communication via the diagnostic protocol, then auto meter program can be completed online updates. Therefore, by this method upgrades and updates to avoid unloading the car dashboard during demolition brought trouble and loss, which greatly facilitates the maintenance of the instrument. At the same time in this thesis read the data download into Flash or EEPROM, compared the data different before and after, ensure the accuracy of the data in Flash or EEPROM, protected the car dashboard normal and safe working.Finally, with actual project, it build a real system test platform to verify all functions the system designed, the system is functioning properly and has been applied to practice, it has a certain value. |
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