The Application Of GPS And GPRS In Vehicle Traveling Data Recorder

With the continuous development of science and technology, automobile become more and more popular in people's daily life. At the same time, with the expanding of city scale, the exchange between them become more and more frequent. Which resulting much problem in traffic congestion, car accidents and other issues. It is important for the transport sector to build a better plan for traffic operation and a real-time monitor for the traffic. Because of this, a new technology named"Vehicle Traveling Data Recorder"(VTDR) was developed as a role of electronic police. This paper uses VTDR as project background, efforts to develop the use of GPS and GPRS in the car application.VTDR also be known as"black box in vehicle". It was installed in the bus, taxi, truck and other modes of vehicles. It can record the speed of vehicles, runtime, mileage and other informations. The data was output as digital signals. It was used for enterprise to strengthen the usage, operation and management of vehicles. It provides traffic safety management and accident analysis, as well as law enforcement. It can send the data back to monitoring center through wireless network anytime.GPS is known as the Global Positioning System, which continuously send its own parameters and time information via satellite. The GPS receiver taken by users can receive these informations and calculated the three-dimensional position, three-dimensional direction, velocity and time information. In this paper, the GPS technology was used to get the positioning data of vehicles.GPRS technology was based on the GSM wireless packet switching technology. it has very obvious advantages in data support services. GPRS technology is a good choice for wireless network transmission system.Because of the terminals need to be installed in the car, the embedded system platform must be choosed. According to the definition of IEEE, embedded systems are used to control or monitor machinery, equipment, factory equipment and other large-scale systems. This definition is according to the use of embedded systems. Usually single embedded system's function was simple, and it's designed for a specific purposes. It's a lot difference from the general-purpose computer. There is more commonly used definition for embedded systems: the embedded system is application-centric, based on computer technology, software, hardware, it can be modified to meet any request of the application system, such as reliability, cost, size, power consumption.The build of embedded Linux system platform is including the environment build, Bootloader upload and Linux kernel configuration and upload. The buid of environment including the establishment of cross-compiler, minicom configuration and host services configuration. For bootloader, the U-boot version is used, which is developed from the ppcboot and ARMboot. And we use the minimum Linux kernel of version 2.6.19. After the kernel configuration, the tftp service will be used to burn it into the target board. The hardware design in this paper is that the GPS reciver, GPRS module and other external equipments are connect to the develop board via serial port. And the master chip is AT91SAM9260 from Atmel Company. The GPS receiver in this paper is iTrax02 from FAStrax Company.It is a GPS OEM board with small size and low power consumption. The GPRS module is GTM900 wireless module from Huawei, which is a tri-band GSM/GPRS wireless module, supporting standard AT commands and enhanced AT commands. This module also provides a wealth of voice and data services and other functions.To carry out software function is the emphasis of this paper, which includes GPS and GPRS modules. Because of the GPS and GPRS modules are connected to target board via serial interface, the operation and control on these two modules are carried out by coding on the serial port. In Linux, equipment exists as a kind of file, and is called device I/O file. Device I/O file are saved under /dev, so as serial port equipment. In general, corresponding device I/O files of serial port I and serial port II are named in turn as /dev/ttyS0 and /dev/ttyS1. Therefore, we can open serial port device by open() function like opening normal files, and get its file description. After open the serial port, some important serial port parameters should be setup. These parameters include baud rate, data bits, stop bits and parity check. After setup, its read and write are just like the normal ones'by executing read() and write() functions. The main function of GPS module contained two aspects: GPS data receving and GPS data analyzing. GPS data receiving is actually reading serial port data. Generally speaking, a frame of received GPS data contains a number of data with different formats. This system only needs the data in $GPRMC format. And the major work of GPS data analyzing is to analyze the data in $GPRMC format, extract the information including TIC timing, latitude and longitude, speed and course, and package this information in the format that the vehicle traveling data recorder can take use of.The main function of GPRS module is to transmitting data via wireless network. In this paper, vehicle terminal controls and operates GPRS module by sending AT commands to the module through serial port, then communicates with the control center. Throughout the process, vehicle terminal just needs communicate with GPRS module without considering the communication between GPRS module and control center. The main steps of its communications include GPRS module initialization, status testing, and data transfer between TCP/IP or GSM modules. Considering system speed may differ from GPRS speed, we take receive queue and send queue as buffer. After received from GPRS module, the data is analyzed and saved into the receive queue waiting for system's processing. When the system needs to send data, put the data into the send queue. Then GPRS extracts the data from send queue, packages them into AT commands, and sends via serial port.The experiment shows this system is basically in line with actual demand. It can successfully access to the GPS data and its GPRS can communicate effectively. This system works well so far. However, system upgrades and feature improvements are necessary for better adapting to technology development and users'needs. This paper argues that the GPS and GPRS modules of this system may be worthwhile to continue the following two aspects of research: In GPS, with the startup of the European Galileo program and China's Beidou plan, the research on GPS based on the above two plans will be future research focus. In GPRS, as the era of 3G is coming, the transition of vehicle traveling data recorder's wireless communication from GPRS to 3G is a general trend, witch is also an important future research direction.