Design And Implementation Of Car Fault Diagnostic Tool Based On Embedded System

With the development of electronic technology, Electrical Control Unit is being used widely in the control unit of vehicles because of its small volume, low cost and high reliability. However, as the control of the vehicle becomes electronically, it brings many problems to the checking and repairing of vehicles. The Car fault diagnostic tool can check and display the problems of electronic vehicles effectively. As a result, this kind of tool is developing rapidly.The thesis explores the design and the realization of a hand-held Car fault diagnostic tool that is based upon embedded system. Firstly, it analyses the importance of Car fault diagnostic tool in the process of diagnosing fault in modern electronic vehicles, demonstrates the demanding condition of Car fault diagnostic tool in the market, and makes a comparison between the function of several mainstream fault diagnostic tool existing in our market at present. Then the thesis introduces fault diagnostic system OBD-Ⅱand EOBD adopted by the electronic vehicles commonly, compares the characteristics of these two systems from the aspects of diagnostic socket and fault code. Furthermore, it gives a detailed explanation of communication protocol (Volkswagen communication protocol) from the points of Physical Layer, Data link Layer and Application Layer.In the section of system design, the conception and function of embedded system, the design proposal of the hardware system of diagnostic tool, as well as the principle and function of each module in the hardware system are touched upon above all in the thesis. Later, the developing environment of the system software is introduced, including the developing instrument and the developing language. And the software system design proposal is the focus. As for each module in the system, the design methods and means of realization of the main functions are analyzed and the crucial functions are demonstrated with flow charts. Finally, the developing trends of fault diagnostic technologies in the future are described in the thesis.