Design of intelligent positioning system based on GPS9808

Abstract: This paper proposes a design scheme of intelligent positioning system with OEM module GPS9808 and MSP430F169 microcontroller as core components. At the same time, the main functions and characteristics of GPS9808 and MSP430F169 are introduced, and the software and hardware implementation method of the object intelligent positioning system composed of GPS9808, MSP430F169 microcontroller and GSM short message module TC35i is given. After testing, the performance of the system has been verified and good results have been achieved.

0 Introduction

In the mobile object monitoring system, it is usually necessary to transmit the positioning data of the mobile object back to the monitoring center through the wireless data communication platform. Commonly used wireless data communication platforms are divided into two categories: public network and private network. Among them, the public network refers to wireless data networks such as GPRS, CDPD, GSM, etc.; the private network refers to the wireless data communication network specially established for the monitoring system. The wireless monitoring system using the public network generally has the advantages of small investment, large coverage, and small system maintenance, but its real-time performance is poor and GPS differential positioning cannot be performed. Using private network systems such as GPS can not only monitor the target, but also use time division multiplexing to transmit data. At the same time, private network systems such as GPS can also make full use of wireless frequency resources, and their transmission speed is fast, real-time performance is good, and GPS differential positioning can be performed, and the positioning accuracy is very high. Therefore, the private network GPS mobile object monitoring system is particularly suitable for military and public security, fire protection, public transportation, financial cash transportation and other occasions with high real-time requirements.

The main function of the data transmission terminal of GPS and other private network systems in the system is to realize GPS differential positioning and wireless communication. This article will introduce the application of Leadtek's OEM module GPS9808 in the intelligent positioning system. The positioning system uses the ultra-low power MSP430 microcontroller combined with the GSM communication module TC35i, and has low power consumption, small size, easy to conceal installation, and can meet the user's multi-functional needs such as timely grasping the status of the monitored object at a long distance.

1 Positioning system hardware structure

The intelligent positioning system uses the GPS9808 module to search for the position, speed and other status information of the object, processes this information and detects the status of the sensor installed in the object through the MSP430F169 single-chip microcomputer, and uses the GSM module TC35i to establish communication and control with the user. Figure 1 shows the hardware implementation composition diagram of this intelligent positioning system. The system includes GPS positioning module, CPU control module, communication module, sensor detection module, sound and light alarm module, power management module, etc. It has the characteristics of small size, low power consumption, and multiple functions. It is a cost-effective intelligent positioning system.

Figure 1 Hardware block diagram of the intelligent positioning system

The GSM communication module in this system uses SIENENS's TC35i. TC35i is a special module designed by SIEMENS for GSM communication. It has voice, data, fax and point-to-point SMS functions, can work in EGSM 900 and GSM 1800 frequency bands, weighs only 10 g, can work normally within the voltage range of 3.5 to 4.8 V, and can input 8 to 20 V/500 mA DC. The module has an automatic charging control circuit inside, and the communication rate is 19.2kbps; the light alarm circuit uses the ISD4004 integrated voice chip and the light-emitting LED, and is implemented by combining the drive and power amplifier circuits, so that voice recording and playback and light flashing can be easily realized, which is used to provide safety prompts and alarms to the monitoring system; the sensor detection circuit is used to detect the object signal and control the power supply according to the instructions; the power management circuit is mainly completed by LP3966 and TC1017. These two power management chips can provide 3.6 V and 3.3 V supply voltages respectively. Their current in the energy-saving shutdown mode is only about 0.05 μA. Using a backup battery to power the system can meet the long-term needs of the system, so it can effectively prevent human damage to the object power supply and improve the safety factor of the system.

2 Main Component Selection

2.1 Main features of MSP430F169

MSP430F169 is a single-chip microcontroller that uses 16-Bit RISC architecture and has a maximum operating speed of 8MIPS. It is a microcontroller designed for low-power applications and can be widely used in portable products and systems that require extraordinary standby time.

MSP430F169 has five power-saving working modes. When recovering from LPM3 standby mode (consuming 2.6 μA@Vcc=3) to normal working mode (consuming 500 μA@Vcc = 3, 1 MIPS), the wake-up time is less than 6 μs. It also allows dual external operating frequency input and integrates a variety of low-power peripheral modules.

The main features of MSP430F169 are as follows:

◇ Contains 60 kB + 256 Byte low-voltage Flash module, which can be used to store the program code and data of the controller. 2 kB of random access memory (RAM) can store data in RAM in LPM4 standby mode;

◇ Built-in basic RC oscillation frequency DCO. When the power supply voltage of the external chip is 3.6 V, its maximum operating frequency is 8 MHz. It allows two independent external operating frequency inputs and can also be connected in series with an external low/high frequency oscillation source.

◇ The timing module can provide a set of watchdog timers, which can reset the system to a set of basic timers and two sets of fully functional 16-bit timers, with optional modes such as up, up and down, continuous, and pause timing;

◇ Contains a 12-bit 8-channel successive approximation (SAR) analog-to-digital converter with a maximum conversion speed of up to 200 kHz, built-in 1.5 V and 2.5 V reference voltages and sample-and-hold circuits, and has an automatic scanning function;

◇ With 2 groups of 12-bit digital-to-analog conversion voltage outputs, the two groups of D/A can be output synchronously by program control;

◇ There is a set of analog voltage comparators inside, which can directly provide the output signal to the timing module for it to capture;

◇ Two sets of USART can be provided, which can be used for asynchronous and synchronous transmission (supporting SPI 3Pin and 4Pin transmission) and I2C interface;

◇ Contains hardware multiplier. When using it, you only need to put the operand into a specific buffer, and the result can be retrieved in the next machine cycle, and the operation process does not require the participation of the processor. It can perform four modes of operation: unsigned (+, -) multiplication, signed multiplication, unsigned multiplication and accumulation, and signed multiplication and accumulation;

◇ It has three internal DMA controllers, which can easily move data between two memory addresses.

2.2 Functions and features of GPS9808

GPS9808 is a powerful and excellent OEM module launched by Leadtek. GPS 9808 has been improved on the basis of maintaining the advantages of previous OEM modules. It is a low-power 12-channel module with small 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 can support standard NMEA-0183 and SiRF binary protocols. The external RF metal protection of the module can ensure the best performance in noisy environments. The dimensions of GPS 9808 are 24×20×2.6 mm, and the power consumption is only 215 mW, which is very suitable for use in systems with high requirements for power consumption and volume. The pin arrangement of GPS9808 is shown in Figure 2, and the functions of each pin are listed in Table 1.

Figure 2 GPS9808 pinout

Table 1 Pin function description of GPS9808

3 Interface circuit of MSP430F169 and GPS9808

The CPU of this system uses the ultra-low power 16-bit processor MSP430F169, which is powered by a low voltage of 1.8 to 3.6 V. In RAM data retention mode, it consumes only 0.2 μA, and in active mode it consumes 330 μA/MIPS. When the crystal oscillator is working at 8MHz, its instruction speed can reach 8 MIPS, and it has powerful processing capabilities. Figure 3 shows the interface circuit between the MSP430F169 microcontroller and GPS9808.

Figure 3 Interface circuit diagram of GPS9808 and MSP430F169

4 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 system can update the latitude, longitude and time data every 5 seconds. This design selects the module's default output RMC data format. When the communication with the satellite is normal, the received data format is as follows:

$GPRMC, 204700, A, 3403.868, N, 11709.432, W, 001.9, 336.9, 170698, 013.6, E*6EThe communication protocol between the user and the positioning system is mainly used to provide functions such as controlling the state of the object and querying the object's location information. The data functions that this system needs to provide from GPS9808 mainly include: object positioning information query, object normal area range setting, object tracking setting, etc. Therefore, generally, all the information that can be provided by the NMEA 0183 communication protocol is not needed, but only the time, longitude and latitude, speed and other data bits that are needed for this design need to be selected.

The software of the entire positioning system is implemented in C language. Due to the large number of functions and the very complex protocol, this article only provides the positioning information of objects that require more GPS9808 data bits. The data format of the sending protocol of this system is listed in Table 2.

Table 2 The data format of sending positioning information (positioning system -> user)

5 Conclusion

This article describes the method and implementation of applying Leadtek's positioning module GPS9808 to the intelligent anti-theft system of objects. It broadens the new ideas for the design of object anti-theft systems. The new intelligent positioning system designed with it 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, and difficult to damage, and users can remotely control the state of objects. It is currently a very practical intelligent anti-theft system for objects. Its reliable performance has been tested and applied in practice, and has achieved good results.