Design and Application of GPS9808 Module in Automobile Anti-theft System
The increase in the number of car theft cases has caused greater economic losses to people. In view of the existing problems, this article introduces in detail the application of Leddtek's latest OEM module GPS9808 in the new intelligent anti-theft system. The anti-theft device uses a combination of ultra-low power MSP430 MCU and GSM communication module TC35i. It has low power consumption and small size, which is convenient for concealed installation.
1 Functions and features of GPS9808
GPS9808 is a powerful and excellent OEM module launched by Leadtek. It has been improved on the basis of maintaining the advantages of the previous oEM module, and it is a low-power 12-channel module with a compact structure and excellent performance. Its hot start time is less than 8 s, reacquisition time is less than 0.1 s; positioning accuracy is less than 5 m in differential mode (DGPS); the interface uses serial TTL level, and the data format supports standard NMEA-0183, SiRF binary protocol. The RF metal protection outside the module ensures the best performance in noisy environments.The size is 24mm × 20mm × 2.6mm, and the power consumption is only 215mW.It is very suitable for systems with high power consumption volume requirements such as automotive electronics. Medium application. The pin layout of GPS9808 is shown in Figure 1, and the function table 1 of each pin is listed.
2 GPS9808 hardware design in car anti-theft system
The anti-theft device uses GPS9808 module to search for car's position, speed and other status information, through MSP430F169 single-chip microcomputer to process these information and detect the status of car key switch, door and other sensors, and use GSM module TC35i to establish communication control contact with users. Its hardware realization composition is shown as in Fig. 2. The device includes a GPS positioning module, a CPU control module, a GPS communication module, a sensor detection module, an acousto-optic alarm module, and a power management module. It has the characteristics of small size, low power consumption and many functions. It is a car anti-theft device with high cost performance. The device mainly constitutes the functions and features of the circuit:
①The GSM communication module adopts Siemens' TC35i. TC35i is a special module designed by Siemens for GSM communication. It has the functions of voice, data, fax and point-to-point SMS. It works in the EGSM900 and GSM 1800 frequency bands and weighs only 10 g. It can work normally in the range of 3.5 ～ 4 · 8 V and can input 8 ～ 20 V / 500 The direct current of mA has an internal charge control circuit, and the communication rate is 19.2 kbps.
â‘¡ The sound and light alarm module adopts ISD4004 integrated voice chip and light-emitting LED, combined with the drive and power amplifier circuit. It can easily realize the voice recording and playback of the anti-theft system and the safety prompt of the flashing light and the alarm function.
â‘¢ The sensor detection module is used to detect signals such as car keys and doors, and at the same time control the power supply and central lock according to the instructions.
④ The power management module is mainly completed by LP3966 and TCl017. The two power management chips provide 3.6 V and 3.3 V power supply, respectively, and the current is only O in the energy-saving shutdown mode. Around 05μA; using the backup battery power supply can meet the long-term needs of the system, which can effectively prevent man-made damage to the car's power supply and improve the safety factor of the anti-theft system.
⑤ CPU uses ultra-low power consumption 16-bit microcontroller MSP430F169. It uses a low voltage of 1.8 to 3.6 V, the power consumption in RAM data retention mode is only 0.2 μA, and the power consumption in active mode is 330 μA / MIPS; when the 8MHz crystal works, the instruction speed can reach 8 MIPS, Has strong processing power. The interface circuit of GPS9808 and the one-chip computer is shown as in Fig. 3.
3 software protocol implementation
The communication protocol between GPS9808 and SCM adopts the NMEA-0183 communication protocol supported by the module, and can provide various optional formats such as GGA, GSA, GSV, RMC, VTG, and GLL. When communicating with GPS, the latitude, longitude, and time data are updated every 5 s, taking into account issues such as actual needs and power consumption. Here, select the default output RMC data format of the module. If the communication with the satellite is normal at this time, the received data format is as follows:
$ GPRMC, 204700, A, 3403.868, N, 11709 · 432, W, 001.9, 336.9, 170698, 013.6, E * 6E
The communication protocol between the user and the anti-theft device mainly provides functions such as controlling the state of the car and querying the location information of the car. The functions that need GPS9808 to provide data are: car location information query, car normal parking area range setting, car tracking setting, etc. Therefore, it does not need all the information provided by the NMEA-0183 communication protocol, but only needs to select the data bit information such as time, latitude, longitude, and speed obtained from it.
The software of the entire anti-theft device is implemented in C language. Due to the many functions and the protocol is very complicated, only the data format of the vehicle positioning information transmission protocol that requires more GPS9808 data bits is given here, as listed in Table 2.
Conclusion
This article describes the implementation method of Leadtek's positioning module GPS9808 applied in the automobile anti-theft system, which broadens the new ideas for the design of the automobile anti-theft system. The new intelligent anti-theft device designed by this method not only has the characteristics of advanced technology, convenience, and powerful functions, but also has the unique advantages of low power consumption, small size, concealed installation, the use of an independent power system, which is not easy to destroy, and the user can remotely control the status of the car. , Is currently a very practical intelligent car anti-theft system. Its reliable performance has been tested and applied in practice, and has achieved good results.
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