LCD Display Inverter

Display Inverter / VGA Board / LCD Controller

Circuit Design of Personal Positioning Terminal System Using GPSOne

At present, the personal positioning system integrating positioning, monitoring and alarm functions mostly adopts GPS/GSM (GPRS) technology. Although the Global Positioning System (GPS) can provide high-precision, global-coverage positioning, it is necessary to ensure that there is 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.

At present, the personal positioning system integrating positioning, monitoring and alarm functions mostly adopts GPS/GSM (GPRS) technology. Although the Global Positioning System (GPS) can provide high-precision, global-coverage positioning, it is necessary to ensure that there is 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 technologies. It is a positioning technology developed by Qualcomm for location-based services and adopts Client/Server mode. It combines wireless assisted A-GPS and advanced forward link AFLT triangulation technology to achieve high-precision, high-availability and high-speed positioning. In environments 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. Based on GPSOne module DTGS-800 and low-power microcontroller 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, the DTGS-800 GPSOne module is selected; in order to reduce the size, power consumption and cost, the main control unit MCU uses an ultra-low power 16-bit microcontroller MSP430F147, and the Display uses LED .The single-chip microcomputer is responsible for controlling the GPSOne module to initiate a positioning request, receiving and analyzing the information sent by the CDMA network control center, obtaining the current longitude, latitude and other information, and sending it to the control center or the operator’s mobile phone in the form of text messages. The main control unit MCU is shown in Figure 2. It includes 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 the low-speed crystal oscillator is used to reduce power consumption; MSP430F147 has 2 serial asynchronous communication interfaces (USART), one of which ( DCD, CTS, DTR, RI, RFR/RTS, TXD, RXD pins) interface is connected to UAR-T1 of DTGS-800, and the other (URXD0, UTXDO) interface is connected to the serial port of PC for system debugging. The nRst, MS, TCK, TDI, TD0 pins are connected to the JTAG socket for program download and online debugging; the key1 and key2 pins are connected to “Help” and reserved keys respectively. The external LED DS3 and LED DS4 are used to indicate low battery power and communication between DTGS-800 and MSP430 respectively; BatTest is used to detect battery power.

The DTGS-800 module is the main body of the positioning terminal. It integrates GPSOne devices and adopts the GPSOne solution for positioning. It supports the separation of RUIM from the machine card, and provides a standard RS-232 data interface and a standard AT command interface for data, voice, and short messages. and fax provide fast, reliable and secure transmission. The module can be powered by an external power supply or a battery. The battery power 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, which are connected to 6 LEDs respectively to indicate new SMS signal, CDMA network signal, GPS signal, CDMA network busy, system power-on and battery charging status; BatGauge is connected to battery test terminal to detect battery temperature. UIM card is a kind of smart card of CDMA mobile phone, its function is similar to SIM card in GSM mobile phone. It supports special authentication encryption algorithm and OTA technology (0ver The Air), and can update and manage the data on the card through the wireless air interface. The UIM card is fixed on the card holder and connected to the outside through the 6 pins of the card holder, as shown in Figure 4, where UIM_RESET and UIM_CLK need to be pulled down through a 100 kΩ resistor, and UIM_DATA needs to be pulled up through a 10 kΩ resistor.

Power Module Circuit Design

The power Battery and Charger modules are shown in Figure 5. The 88th and 90th pins of the DTGS-800 module are dedicated power input pins for battery power supply. If the module can be powered by both an external power supply and a battery, the external power supply can be connected to pins 87 and 89, and the battery can be connected to pins 88 and 90. At this time, the external power supply can also charge the battery through the internal power management device of the module. When the module is only powered by battery, a power on signal needs to be given to the module; when the pin is triggered for the second time, the module is powered off. The software design of the terminal has five modules: main program, key detection, battery detection, storage and serial communication.

The main program module is responsible for the initialization and data processing and storage of the other four modules. This module judges the correctness of the received data, extracts the location and other useful information from it, realizes the separation of the data and the temporary storage of the valid data in the on-chip RAM, and sends the useful information to the DTGS8-800 through the serial port. form to a third party. When the system starts, initialize first, including watchdog, timer, voltage detection module (including MD converter), UART, key detection module and DTGS-800 initialization; after system initialization is completed, if there is no interrupt request, it will enter low Power mode to save power. Both the key detection module and the battery detection module are executed in interrupt mode. When a key is pressed, an interrupt will be generated, and the controller will be notified to scan, determine which key is pressed, and then perform corresponding processing; the battery detection module detects the battery power at a certain time interval, and informs the controller if the battery power is insufficient. Start counting, if the low voltage state is detected continuously for more than a certain number of times, the corresponding LED will flash to remind the user to charge.

If the user sends the alarm information, that is, presses the Help key, an interrupt request is generated, the interrupt service subroutine is executed, the system exits the low power consumption mode, enters the “HELP” state, initiates a positioning request, receives and parses the positioning information, and converts the useful information to the “HELP” state. After the alarm information is packaged, it is sent to the server designated by HelpNum in the form of a short message. After the sending is successful, the system enters the low power consumption mode. If a third party initiates a positioning request, the system exits the low power consumption mode, enters the “MPC positioning” state, initiates a positioning request, receives and parses the positioning information, and sends useful information to the designated mobile phone or server in the form of text messages. Return to low power mode. The service password and the address of the MPC can be set remotely in a specific format via SMS.

Based on GPSOne module DTGS-800 and low-power microcontroller MSP430F147, this paper designs and implements a personal positioning terminal that integrates personal positioning, monitoring and alarm, and solves the problem that GPS cannot be positioned indoors, tunnels and other occasions. Due to the use of low-power processors, the overall system power consumption is minimized. It can work on standby for a long time, which brings great convenience to users and has high practical value. But because the system uses the short message channel of the CDMA network to transmit information, the real-time performance is not ideal. In order to improve the real-time performance of the system, consider using the built-in TCP/IP protocol of the GPSOne module for information transmission.

The Links:   NL8060BC3142E 7MBR100VX120-51