Application of MSP430 and GPS99808 module in automobile anti-theft system

　　With the development of social economy, the number of users who travel by car is increasing, and the number of car thefts is also increasing, which has caused great economic losses to people. In view of the existing problems, this article introduces in detail the application of Leadtek's latest OEM module GPS9808 in the new intelligent anti-theft system. The anti-theft device uses the ultra-low power MSP430 microcontroller combined with the GSM communication module TC35i. It has low power consumption and small size for concealed installation. At the same time, it meets the user's multi-functional needs such as timely grasping the safety status of the car from a long distance.

　　1. Functions and features of GPS9808

　　GPS9808 is a powerful and high-performance OEM module launched by Leadtek. It has been improved on the basis of maintaining the advantages of previous OEM modules. It is a low-power 12-channel module with compact structure and excellent performance. Its hot start time is less than 8 s, and the recapture time is less than 0.1 s; the positioning accuracy is less than 5 m in differential mode (DGPS); the interface adopts serial TTL level, and the data format supports standard NMEA-0183 and SiRF binary protocols. The RF metal protection outside the module ensures the best performance in noisy environments; the external dimensions are 24mm×20 mm×2.6mm, and the power consumption is only 215 mW, which is very suitable for use in systems with high power consumption and volume requirements such as automotive electronics. The pin distribution of GPS9808 is shown in Figure 1, and the functions of each pin are listed in Table 1.

　　2 Hardware Design of GPS9808 in Car Anti-theft System

　　The anti-theft device uses the GPS9808 module to search for the car's location, speed and other status information, processes this information and detects the status of sensors such as the car key switch and the car door through the MSP430F169 single-chip microcomputer, and uses the GSM module TC35i to establish communication control with the user. Its hardware implementation composition is shown in Figure 2. The device includes a GPS positioning module, a CPU control module, a GPS communication module, a sensor detection module, an audio and light alarm module, and a power management module. It has the characteristics of small size, low power consumption, and multiple functions. It is a cost-effective car anti-theft device.

　　Functions and features of the main components of the device:

　　① The GSM communication module uses Siemens' TC35i. TC35i is a special module designed by Siemens for GSM communication. It has voice, data, fax and point-to-point SMS functions, works in the EGSM900 and GSM 1800 frequency bands, weighs only 10 g, can work normally in the range of 3.5 to 4.8 V, can input 8 to 20 V/500 mA DC, has an automatic charging control circuit inside, and the communication rate is 19.2 kbps.

　　②The sound and light alarm module adopts ISD4004 integrated voice chip and luminous LED, combined with drive and power amplifier circuit, which can easily realize the voice recording and playback of the anti-theft system and the safety prompt and alarm functions of flashing lights.

　　③The sensor detection module is used to detect signals from car keys, car doors, etc., and control the power supply, central lock, etc. according to instructions.

　　④The power management module is mainly completed by LP3966 and TC1017. The two power management chips provide 3.6 V and 3.3 V power supply respectively. In the energy-saving shutdown mode, the current is only about 0.05μA; using the backup battery to power the system can meet the long-term needs, which can effectively prevent human damage to the car power supply and improve the safety factor of the anti-theft system. [page]

　　⑤CPU uses ultra-low power 16-bit single-chip microcomputer MSP430F169. It uses 1.8~3.6 V low voltage, and consumes only 0.2μA in RAM data retention mode and 330μA/MIPS in active mode; when the crystal oscillator is working at 8MHz, the instruction speed can reach 8 MIPS, which has powerful processing capabilities. The interface circuit between GPS9808 and single-chip microcomputer is shown in Figure 3.

　　3 Software Protocol Implementation

　　The communication protocol between GPS9808 and the microcontroller adopts the NMEA-0183 communication protocol supported by the module, which can provide multiple optional formats such as GGA, GSA, GSV, RMC, VTG, GLL, etc. When communicating with GPS, considering the actual needs and power consumption, the latitude and longitude and time data are updated every 5 seconds. Here, the module's default output RMC data format is selected. 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 car status and querying the car location information. The functions that require GPS9808 to provide data mainly include: car positioning information query, car normal parking area range setting, car tracking setting, etc. Therefore, all the information provided by the NMEA-0183 communication protocol is not needed, and only the time, longitude and latitude, speed and other data bits that can be used need to be selected from it.

　　The software of the entire anti-theft device is implemented in C language. Due to the large number of functions and the very complex protocol, only the vehicle positioning information sending protocol data format 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 in the intelligent car anti-theft system, which broadens the new ideas for the design of car anti-theft systems. 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, easy concealed installation, independent power supply system, not easy to be damaged, and users can remotely control the car status. It 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.