0. Introduction
With the rapid development of modern society, the popularity of private cars is constantly increasing. Currently, private cars have become an indispensable means of transportation for the vast majority of citizens. However, the resulting vehicle safety issues, such as vehicle theft, constantly trouble car owners. How to achieve real-time monitoring and control of vehicles is a problem that car owners are generally eager to solve. To address this issue, we have developed a vehicle positioning control system, which greatly facilitates car owners in monitoring and controlling the status of their vehicles.
1. Functions of the vehicle positioning control system
The vehicle location control system can provide vehicle owners with real-time vehicle location information, safety status, and current vehicle status. The functions of the vehicle location control system are as follows:
1) Information collection function
The vehicle positioning control system can accurately collect real-time information about the vehicle (such as longitude, latitude, speed, direction, etc.).
2) Data storage function
It can store information such as vehicle ID number, speed information 5 minutes before parking, and continuous driving time.
3) Data transmission function
The system can transmit real-time vehicle information collected via GPRS to designated target PCs and mobile phones, allowing vehicle owners to monitor the vehicle's location and status in real time. Furthermore, vehicle owners can issue control commands to the vehicle positioning and control system via PC or mobile phone, such as stopping the vehicle or cutting off fuel, ensuring effective control of the vehicle even after it is stolen.
2. System Hardware Design
The system uses the MSP430F147 microcontroller as its core controller and integrates a GPS module, a GPRS module, a serial memory module, and a power management module. The system block diagram is shown in Figure 1.
Figure 1 System Block Diagram
2.1 Microcontroller Unit
The system uses TI's MSP430F147 microcontroller as the core controller [1]. This microcontroller has a 16-bit CPU integrated register and a constant generator, which enables the microcontroller to achieve maximum code efficiency; it integrates JTAG and supports online programming; two general-purpose full-duplex serial synchronous/asynchronous communication interfaces; six 8-bit I/O ports; and an external interrupt input interface. The microcontroller's serial port 0 is responsible for receiving the data information output by the GPS module, analyzing and extracting the received valid information data, storing the data on the one hand, and sending the information to the specified target address through the GPRS module on the other hand.
2.2 GPS Module
2.2.1 GPS Overview
GPS (Global Positioning System) is a new generation satellite navigation and positioning system developed by the United States. It can provide continuous, real-time, and high-precision three-dimensional position, three-dimensional velocity, and time information to users worldwide. It is currently the world's most accurate navigation system and has been widely used in military, economic, geographic information measurement and control, and other fields. The GPS positioning system consists of three parts: the GPS satellite constellation (space segment), the ground monitoring system (ground control segment), and the GPS signal receiver (user equipment segment).
2.2.2 Introduction to GPS Module
GPS uses the GS-87 module [2], which is a high-efficiency, low-power intelligent satellite receiver module or satellite receiver engine. It uses the third-generation satellite positioning receiver chip designed by SiRFstarIII, a US company, and is a complete satellite positioning receiver with all-round functions. Its system structure is shown in Figure 2. The GPS antenna receives satellite signals and converts weak electromagnetic wave energy into corresponding current. The current is amplified by the LNA (low noise amplifier), and then its frequency is converted by the filter and sent to SIRFStarIII (composed of GRF3W and GSP3) for processing. The processed signal is connected to the microcontroller through the serial port. The user processes the information received by GPS and extracts the information useful to the user by controlling the microcontroller through software programming.
Figure 2 System Structure Diagram
2.3GPRS module
2.3.1 GPRS Overview
GPRS (General Packet Radio Service) is a wireless packet switching technology based on the GSM (Global System for Mobile Communications) system, providing end-to-end, wide-area wireless IP connectivity. It is one of the implementations of the GSMP Phase 2.1 specification and can provide a higher data rate than the existing GSM network's 9.6 kbit/s. GPRS uses the same frequency bands, bandwidth, burst structure, radio modulation standards, frequency modulation rules, and the same TDMA frame structure as GSM. Therefore, building a GPRS system on top of a GSM system only requires adding some hardware and upgrading the software. The method for building a GPRS system is as follows: 1) GPRS is implemented on the existing GSM network, introducing three main components: the Serving GPRS Supporting Node (SGSN), the Gateway GPRS Supporting Node (GGSN), and the Packet Control Unit (PCU). 2) Upgrade the relevant GSM components using software.
GPRS data transmission has the following characteristics:
(1) It uses time-packet switching technology for communication. (2) It charges based on data flow, not online time. (3) It has a high transmission rate. (4) It is always online. (5) GPRS network access speed is fast, providing seamless connection with existing data networks. (6) GPRS supports applications based on standard data communication protocols and can interconnect with IP networks and X.25 networks. (7) The design of GPRS allows it to support both intermittent burst data transmission and occasional large data transmission.
2.3.2 Introduction to GPRS Module
The GPRS module uses Siemens' MC52i module [3], which is an important part of establishing communication between the vehicle positioning control system and the PC and mobile phone. Through the GPRS module, the vehicle location information (such as time, longitude, latitude, speed, direction, etc.) collected by the GPS module can be sent to the PC in real time; on the other hand, it can also receive control commands from the PC. This realizes two-way communication between the vehicle positioning control system and the PC and mobile phone.
2.3.3 GPRS Interface Circuit Design
The MC52i module is connected to the MSP430F147 via a serial port and signal control pins, as shown in Figure 3. Pins 26-30 of the MC52i are the power supply input terminals, with an input voltage range of 3.3V to 4.8V and a peak load current of 2A. The TXD0 and RXD0 pins of the MC52i module are the data receive and data output ports, respectively, and are connected to the TXD1 and RXD1 pins of the microcontroller's serial port (UART1). Pins 1-6 of the MC52i provide a standard interface for an external SIM card. CCGND and CCVCC provide the operating voltage for the SIM card; CCCLK provides the clock pulse signal for the SIM card; CCIO is the serial data input/output interface; CCRST is the SIM card reset signal; and the CCIN pin is mainly used to detect whether the SIM card is inserted into the SIM card slot.
