| In order to get rid of dependence on GPS in the application of satellite navigation system, china is taking a positive attitude to carry out the research of the Beidou System, Around 2020, china hopes to cover the whole world with the Beidou navigation system. By then, the security, effective and real-time positioning information service provided by the Beidou navigation system can be obtained in the whole world. Facing the good situation of domestic market development, during the year of 2012 to 2013, the ministry of communications has made the corresponding technical requirements for the vehicle traveling data recorder based on the Beidou navigation. Including specification for design of vehicle traveling data recorder GB/T 19056-2012 and satellite positioning system for road transport vehicles Beidou compatible vehicle terminal communication protocol technical specification. In this design, in order to make the terminal equipment and the existing monitoring platform can be effective communicate, the internal software in the organization of the relevant data will also be based on the provisions of the ministry of communications on the communication protocol.In the stage of the hardware design process, all the requirements of the hardware is according to the design specification of the vehicle traveling data recorder, the selection of each module is based on the actual demand for guidance. Modules include key input and liquid crystal display device, thermal printer, Beidou positioning chip, communication module and IC card storage of driver information. According to the requirement of the design code, the terminal equipment should have the function of the relevant information data of internal storage. Therefore, this design has joined the USB and the serial port 232 interface. Taking into account the special environment of the running process of the vehicle equipment, we need to introduce the related shielding circuit to reduce the electromagnetic interference caused by the vehicle itself in the hardware design, and this paper puts forward the solution.At the same time, because the device itself has a large number of modules and code, in order to facilitate the management of the management of the driving function of each module and the local variables and reduce the interference between each other, programming mode is C/C++ mixture for the encapsulation of object-oriented language. The RTX Keil real time operating system is used in software design, the system establishes a task for each of the different functions, through clock timing and task scheduling, each task take 10 ms as cycle, to ensure the integrity of the equipment in real time. In addition to the standard set of related functions, the corresponding practical functions are developed for the specific condition of the equipment, such as serial port debugging and internal parameters of serial port settings, the equipment for a long time can't locate the situation of the positioning then the module self reset function, etc, the stability of equipment is improved effectively. In the application aspects of the design has achieved some key technical problems, including GPRS remote upgrade and remote GSM SMS debugging function and record internal data storage and U disk is derived for the technology, based on Markov chain data upload timing, under different application condition of the Chinese character font scaling, and so on.After a lot of experiments and simulation tests, the result shows that the system is stable, and can make judgments on the simple hardware problems. In terms of software, the ability of data exchange and data analysis can be realized between the test platform, and effective storage device related information. After the U disk is triggered to sixteen Hex file format will be recorded information derived, related design functions satisfied the expected requirements. |
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