In recent years, with the rapid development of urban public transport, the method of domestic bus reporting has been greatly improved, and the traditional ticket seller shouting to report stations has gradually become the driver manually using the stop device to report stations.
Although the manual stopper is more convenient to use, but because the driver needs to report the stop on the premise of ensuring safe driving, it often happens that the stoppage is not timely, even wrong or missed, and the driver is allowed to drive during the driving process. There are also potential safety hazards in reporting the station. The automatic stop reporting method can greatly reduce the driver's workload and promote the modernization process of the bus system. To realize automatic station reporting, the location of the bus needs to be measured in real time to determine whether the bus has reached the station. The GPS can be used to determine the geographic location of the bus. It is only necessary to compare the current location with the location data (latitude and longitude) of the bus station to know whether the bus has arrived at the station, making the station reporting system intelligent. This kind of GPS-based intelligent station reporting system can eliminate the hidden dangers caused by the driver's attention during the driving process. It is particularly suitable for China's national conditions, which have become increasingly severe due to the rapid development of the automobile industry, and can also introduce relevant introductions of city attractions on key routes. The system has great potential in the field of GPS navigation and business, and has broad development prospects.
1 System solution
The GPS-based bus intelligent reporting system is a combination of mobile communication technology and GPS technology. The entire system consists of the S3C24l0ARM9 (Advanced Simplified Instruction Set Machine) development board, SIM548CGPS / GPRS module, voice broadcast module, AT89S52 single-chip microcomputer, and OCMJ5X10B LED ( Light-emitting diode) backlight wide temperature yellow-green screen and other devices. The GSM / GPS module is composed of a GPS sub-module and a GSM (Global System for Mobile Communications) sub-module. The GPS module is responsible for GPS data reception. When the bus is traveling, the measured information of the GPS module is compared with the stored position information to automatically report the station. Without human intervention, it can also play certain information at a fixed location, such as ride prompts and advertising information. Wait. The GSM module is used for data communication between the bus and the dispatch room, to realize the joint dispatch of the bus, and to realize the dispatch function of the dispatch center to the bus.
The voice broadcast module is responsible for voice playback, providing voice playback such as entry and exit and prompt information. The SCM module controls the key scan and LCD display.
1.1 Hardware design
The system hardware part is mainly composed of the S3C2410ARM9 development board, GPS / GSM module, power amplifier module, display module, voice playback module and corresponding peripheral circuits. The GPRS module and GPS module are connected to the ARM processor through RS232 (serial port), while the LCD (liquid crystal display) module is controlled by the single-chip microcomputer to communicate with the ARM through the serial port, and the voice playback module through IIS (InterICSound) and SPI (serial peripheral interface ) Communicate with ARM. The hardware connection mode is shown in Figure 1.
Figure 1 System hardware structure
The GSM / GPS module uses the GPS / GSM module from SIMCOM. This module is a quad-band GSM / GPRS (General Packet Radio Service Technology) wireless module and supports SiRFStarIIIAGPS technology.
The integration of GSM / GPRS and AGPS technology makes this module suitable for GPS tracking, navigation, monitoring and management of equipment and assets such as vehicles and ships, and other GPS applications. The keyboard scanning and screen display are processed by the microcontroller. The keyboard display board mainly implements keyboard scanning, LCD screen display and communication with the ARM processor module. The overall block diagram of the hardware system is shown in Figure 2.
Figure 2 System composition
1.2 Overall software design
The main functions of the system are controlled by ARM, programmed in C language, and multi-threaded processing related functional modules. The implementation process is as follows:
After the system is initialized, it calculates location, reports stations and reads related information based on GPS positioning information and line information stored in the system. The display module in the vehicle is controlled by ARM for display, voice playback and data transmission to the data center.
2 Design and implementation
2.1 System initialization
Before the system runs, each part must be initialized with a software program. The initialization includes the following parts:
ARM and system initialization;
Display button module initialization;
Initialization of external devices and interfaces: mainly initialization of GPS, GPRS and voice chips;
Software system initialization: set global variables, pointers and arrays, data structures, and bus information initialization.
The system software part mainly detects GPS information in the main program, determines the current geographic location of the bus, and then decides whether to play voice messages. At the same time, it also needs to realize the functions required by the buttons, such as switching to manual broadcasting. The software part of the system is developed based on the Linux development environment. According to the functions to be completed by the system and the running status of each module, the main program part adopts multi-thread and message queue mode, which can receive GPS data in time.
Because only the data of the GPRMC frame is used, the data volume of the serial communication is not large, and the communication and data processing process is relatively fast. The system can timely broadcast the station and other voice information. The latitude and longitude data of each station passing by the bus needs to be measured in advance and stored in the data area of ​​the system for comparison and reference. GPRS information is transmitted through the serial port, using the query method, and the buttons are also received using the query method to determine which function key is pressed. The software is written in C language and burned into Flash after successful debugging to achieve offline operation.
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