Design of Positioning Monitoring System Based on SOC Microcontroller

This paper discusses the design of positioning monitoring system based on SOC single chip technology. The system consists of two parts: positioning terminal and monitoring center. The positioning terminal uses C8051F021 as the core microprocessor, and communicates serially with SIEMENS M-C35i GPRS module and GR-87 satellite receiving module through two serial ports, receives positioning data sent by GPS receiver and controls SIEMENS MC35i GPRS module. The system uses watchdog circuit to ensure the normal operation of the controller. The positioning information collected by the positioning terminal is sent to the monitoring center in the form of SMS through GPRS network. This paper uses VC as the development platform and VC++ for MapX secondary development to produce electronic maps, thereby realizing the collection, processing and display of positioning information in the monitoring center. The actual positioning process shows that the system has high positioning accuracy and fast information transmission rate.

1 Overall system design

The design is mainly composed of the SoC technology-based single-chip microcomputer C8051F021, SIEMENS MC35i GSM/GPRS module and GR-87 satellite receiving module. The positioning terminal uses C8051F021 as the core controller, and controls the SIEMENS MC35i GSM/GPRS module and GR-87 satellite receiving module for serial communication through two serial ports UART0 and UART1, and controls the SIEMENS MC35i GSM/GPRS module to send data to the monitoring center in the form of GPRS service. The SoC single-chip microcomputer C8051F021 receives the positioning information from the GR-87 satellite receiving module, verifies the received information, selects the required information and adds the corresponding code to form a data packet, and then stores them in the built-in FLASH of C8051F021 (there is a temporary storage for data only on the program storage FLASH).

The acquisition, processing and display of positioning information are completed on the host computer by the electronic map. The monitoring center processes and displays positioning information by calling the interface function of MapX to realize a series of functions of the electronic map.

SIEMENS MC35i GSM/GPRS module has two data working modes: SMS and GPRS communication. The module power-on startup process is 3 to 5 seconds. If the SIEMENS MC35i GSM/GPRS module is connected to a valid SIM card, the module will be attached to the GPRS network and request the module to send the longitude and latitude information to the monitoring center in the form of a short message through the serial port in the form of AT commands. Of course, the monitoring center can also send related instructions to the SoC microcontroller through the module. The SoC microcontroller analyzes the received instructions and then makes corresponding processing through the I/O port. The system structure diagram is shown in Figure 1.

2 System Hardware Implementation

2.1 Implementation of the core controller

The single-chip microcomputer used in the system is the SoC single-chip microcomputer C8051F02X produced by CYGNAL. This single-chip microcomputer is an integrated mixed-signal system-level chip with a microcontroller core compatible with 8051 (operating speed up to 25 MIPS) and fully compatible with the MCS-51 instruction set; the C8051F single-chip microcomputer has an on-chip debugging circuit, which can be non-invasively and full-speed in-system debugging through the 4-pin JTAG interface; the C8051F high-speed SoC chip also integrates almost all analog and digital peripherals and other functional components required to constitute a single-chip microcomputer control system (including ADC, DAC, programmable gain amplifier, voltage comparator, voltage reference, temperature sensor, SMBus/I2C, UART, SPI, timer, programmable counter/timer array PCA, internal oscillator, watchdog timer and power monitor, etc.). The high integration of these peripherals provides great convenience for designing small-volume, low-power, high-reliability, and high-performance single-chip microcomputer application systems, which can greatly reduce the overall cost of the system.

The controller uses the serial port to communicate with GPS and GPRS; it brings out the JTAG serial interface, which is a full-speed, non-intrusive system debugging interface (on-chip), through which the internal FLASH memory of the controller can be system-programmed and can communicate with the on-chip debugging support circuit.

This system configures the P0.0, P0.1, and P0.4 of the microcontroller as the input, output, and start of the GPRS module, and receives and sends positioning information after starting the GPRS through the transistor; P0.2 and P0.3 are configured as the input and output of the GPS module to obtain positioning information. [page]

MC35i is a new generation of wireless communication GPRS module launched by SIEMENS. The MC35i module is mainly composed of 6 parts: GSM baseband processor, GSM radio frequency module power supply module (ASIC), FLASH, and ZIF connector antenna interface. The unique 40-pin ZIF connector realizes the bidirectional transmission of power supply, connection instructions, data, voice signals and control signals. The SIM card holder and antenna can be connected respectively through the ZIF connector and the 50 Ω antenna connector. The 40 pins of MC35i are connected to the power circuit, startup and shutdown circuit, data communication circuit, voice communication circuit, SIM card circuit, status indicator circuit, etc. through the ZIF connector. The peripheral interface circuit of MC35i is shown in Figure 2.

2.3 GR-87 Satellite Receiver Module

GPS signal receiver function: capture the signal of the satellite to be measured selected according to a certain satellite height cutoff angle, and track the movement of these satellites, transform, amplify and process the received GPS signal, so as to measure the propagation time of the GPS signal from the satellite to the receiver antenna, interpret the navigation message sent by the GPS satellite, calculate the three-dimensional position of the measuring station in real time, and even the three-dimensional speed and time, and finally output the positioning data through the standard I/O port. This system uses the GR-87 satellite receiving module of Taiwan Changtian Technology Co., Ltd. (HOLUX) to obtain positioning data. The output statements of the GPS receiver are all in accordance with the serial communication protocol, the data format is 8 data bits, 1 start bit, 1 stop bit, no parity check, and the baud rate can be selected as needed. The baud rate of this system is 4 800 b/s. In this system, NMEA format messages are received as raw data input, and its output frequency is 1 Hz. The output data uses ASCII character code, and there are more than a dozen output statements, including GGA, GSA, GSV, RMC, RMT, VTG, etc. These positioning data sentences not only provide information such as position, speed, time, etc., but also indicate the local satellite reception conditions. Among them, the GGA positioning data sentence is the most commonly used.

3 System Software Design

3.1 Software Implementation of Positioning Terminal

The software of the positioning terminal adopts a modular design method, and its modules mainly include system initialization, GPS positioning information processing, and GPRS positioning information sending. The processing of GPS positioning information is executed in the interrupt mode of serial port UART1, and the sending of GPRS positioning information is executed in a cyclic manner.

The system initialization includes system clock initialization, port initialization, serial port initialization and GPRS startup. System clock initialization uses an external crystal oscillator 22.118 4 MHz without frequency division; port initialization configures the cross switch and assigns port pins to URAT0 and URAT1; serial port initialization sets the serial port working mode and calculates the timer value through the baud rate of GPS and GPRS.

3.2 Software Implementation of Host Computer

The monitoring center is developed by embedding the GIS software MapInfo into VC6, which allows the map window in MapInfo to be merged into VC, thereby taking advantage of VC's powerful database functions and MapInfo's intuitive and visual processing advantages of geographic information. By calling the interface functions of MapX, some basic functions of the electronic map are realized. A program is written to connect the positioning terminal and the monitoring center, and the positioning information obtained by the positioning terminal is displayed on the electronic map.

4 Experimental Results

This paper uses the positioning monitoring based on SOC technology in the actual positioning process and tests the positioning monitoring. The positioning area is selected as the road in front of the library of Wuhan University of Science and Technology. The experimental results are shown in Figure 3.

As can be seen from Figure 3, the system operates well and meets the positioning requirements of positioning monitoring.

5 Conclusion

This paper implements the design of GPS/GPRS positioning monitoring based on advanced SoC technology, and describes the hardware and software structure of the system in detail. The core controller C8051F021 is used to control the GPS module and GPRS module. VC++ is used for secondary development of MapX, and the map window in MapInfo is merged into VC, which takes advantage of the powerful database function of VC and the intuitive and visual processing advantage of MapInfo for geographic information.