Circuit Design of Personal Positioning Terminal System Using GPSOne Technology

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At present, the personal positioning system integrating positioning, monitoring and alarm functions is mostly based on GPS/GSM (GPRS) technology. Although GPS (Global PosiTIoning System) can provide high-precision, global coverage, there must be a direct path between the GPS receiver and the satellite, which makes the GPS positioning system in densely populated urban areas and buildings. There is a blind spot inside the object. GPSOne integrates GPS, CDMAlX (Code Division Multiple Access Packet Data Exchange Network), GIS (Geographic Information System) and Internet technology. It is a positioning technology developed by Qualcomm for location-based services, using Client/Server. It combines wireless-assisted A-GPS and advanced forward-link AFLT triangulation technology for high-precision, high-availability and high-speed positioning. In an environment where A-GPS positioning technology cannot be used, it will automatically switch to AFLT triangulation technology to ensure the success rate and accuracy of positioning. Here, based on the GPSOne module DTGS-800 and the low-power single-chip MSP430, a personal positioning terminal with positioning, monitoring and alarm functions is designed and implemented.

In order to solve the problem that GPS is difficult to locate in indoor and high-rise building dense areas, DTGS-800 GPSOne module is selected. In order to reduce the size, reduce power consumption and cost, the main control unit MCU selects the ultra-low power 16-bit single-chip MSP430F147, and the display selects LED. . The MCU is responsible for controlling the GPSOne module to initiate a positioning request, receiving and parsing the information sent by the CDMA network control center, obtaining the current latitude, longitude and other information, and sending it to the control center or the operator's mobile phone by means of a short message. The main control unit MCU is shown in Figure 2. It includes the MSP430F147, an external high-speed crystal oscillator and a low-speed crystal oscillator. When high-speed processing is not required, the high-speed crystal oscillator can be turned off, and only a low-speed crystal oscillator can be used to reduce power consumption. The MSP430F147 has two serial asynchronous communication interfaces (USART), one of which (USART) The DCD, CTS, DTR, RI, RFR/RTS, TXD, and RXD pins are connected to the UAR-T1 of the DTGS-800, and the other (URXD0, UTXDO) interface is connected to the serial port of the PC for system debugging. The nRst, MS, TCK, TDI, and TD0 pins are connected to the JTAG socket for program download and online debugging; the keyl and key2 pins are respectively connected to "Help" and reserved buttons. The external LED DS3 and LED DS4 indicate the low battery and communication between the DTGS-800 and the MSP430, respectively; BatTest is used to detect the battery power.

The DTGS-800 module is the main body of the positioning terminal. It integrates GPSOne device and uses GPSOne solution to locate. It supports the separation of RUIM from the machine card. It provides standard RS-232 data interface and standard AT command interface for data, voice and short message. And faxing provide fast, reliable, and secure transmission. The module can be powered by external power supply or battery. The battery supply voltage is +4.0 V±10%, and the external power supply voltage is +4.5 V±10%. The external power supply can also charge the battery through the power management device inside the module. .

The circuit of the DTGS-800 module is shown in Figure 3. Among them, DCD, CTS, DTR, RI, RFR/RTS, TXD, RXD pins are connected to UART1 of MSP430F147, which is the communication channel between DTGS-800 and MSP430F147; UIM_DATA, UIM_CLK, UIM_PWR_EN, UIM_RESET are connected to UIM card; Sgl_SMS, Sgl_IDEL, Sgl_GPS, Sgl_busy, Sgl_Power, Sgl_ch-arge are system status indication signals, respectively connected to 6 LEDs for indicating new SMS signal, CDMA network signal, GPS signal, CDMA network busy, system power-on and battery charging status; BatGauge battery test End, used to detect battery temperature. The UIM card is a smart card for CDMA mobile phones, which functions like a SIM card in a GSM mobile phone. It supports dedicated authentication encryption algorithm and 0TA technology (0ver The Air), which can update and manage the data on the card through wireless air interface. The UIM card is fixed on the deck and connected to the outside through the 6 pins of the deck. As shown in Figure 4, UIM_RESET and UIM_CLK are pulled down by a 100 kΩ resistor, and UIM_DATA is pulled up by a 10 kΩ resistor.