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Bus Station Car GPS System of Intelligent Design

In Electronic Infomation Category: B | on April 12,2011

Recent years, with the rapid development of urban public transport, bus stations China has improved a lot the way, the conductor shouted from the traditional reporting stations are becoming the driver manually using the bus stop bus stop.

Although the manual uses the more convenient bus stop, but because the drivers need to ensure the safety of driving under the premise of the stops, so the stops often not timely, or even false statements and MT48LC4M16A2TG-75 datasheet and omissions of the phenomenon, and MT48LC4M16A2TG-75 price and so the pilot driving during the process of the stops there are also security risks. Way of automatic reporting stations can greatly reduce pilot workload, and MT48LC4M16A2TG-75 suppliers and promote modernization of the public transportation system. To achieve automatic station, you need to measure real-time location of buses in order to determine whether the bus has reached the site. Using GPS to determine the location of the bus, just the current location of the location of bus stops with the data (longitude and latitude) compared to know whether the bus to reach the site, making the bus stop system has a certain intelligence. GPS-based intelligent reporting system to eliminate the driver stops driving the process due to both the stops and bring the hidden devices. Particularly suitable for the rapid development of the automotive industry increasingly serious traffic problems caused by conditions in China, but also in key spots on the line to join the urban landscape of related presentations. The GPS navigation system in the areas and commercial areas have very great potential, and has broad prospects for development.

1 system program

GPS-based bus stop announcement system is a smart mobile communication technology and the combination of GPS technology, the entire system consists of S3C24l0 ARM9 (Advanced RISC Machine) development board, SIM548C GPS / GPRS module, the voice broadcast module, AT89S52 Microcontroller and OCMJ5X10B the LED (light emitting diode) backlight wide temperature range devices such as yellow and green screen composition. GSM / GPS module is divided by the GPS module and GSM (Global System for Mobile Communications) sub-module. GPS module is responsible for receiving GPS data. In the process of moving the bus, GPS module, the measured information with stored location information can be carried out to compare the stops automatically, without human intervention, can achieve in a fixed position to play some specific information, such as travel tips, advertising information and so on. GSM module and the control room for the bus between the data communications bus to achieve the joint scheduling, dispatching center to achieve the scheduling of buses.

Voice broadcast voice playback module is responsible for providing prompt information access points and voice playback. MCU module control buttons and LCD display scan.

1. 1 hardware design

System hardware mainly by the S3C2410 ARM9 development board, GPS / GSM module, power amplifier module, display module, voice playback module and the corresponding peripheral circuit. GPRS module and GPS module are via RS232 (serial port) is connected with the ARM processor, and LCD (liquid crystal display) module by the ARM microcontroller through the serial port and communications, voice playback module IIS (Inter IC Sound), SPI (serial external based interface) and ARM communications. Hardware connections shown in Figure 1.

Figure 1 System hardware architecture

GSM / GPS modules SIMCOM companys GPS / GSM module, the module is a quad-band GSM / GPRS (General Packet Radio Service technology) wireless module, while supporting SiRF Star III AGPS technology.

GSM / GPRS and integrated AGPS technology enables the module to meet the GPS tracking, navigation, marine vehicles and other equipment and asset monitoring and management, and other GPS applications. Keyboard scanning and display data processing done by the microcontroller. Main achieved keyboard keyboard scan display panel, LCD screen display and to communicate with the ARM processor module. The overall block diagram of the hardware system shown in Figure 2.

Figure 2 system components

1. 2 software design

System functions controlled by the ARM using the C programming language, multi-threading related modules. Implementation of the relevant process is as follows: The system initialization is complete, information and systems based on GPS positioning information to calculate the line storage location, station and read the information reported by the ARM control of the car display module for display, audio playback, and the data center for data transfer.

2 Design and Implementation

2. 1 system initialization

The system is running, you must use the software to initialize the various parts. Initialization includes the following sections:

ARM and system initialization; display button module initialization; external device, the interface initialization: mainly GPS, GPRS, and voice chip initialization and other equipment; software system initialization: setting global variables , pointers and arrays, data structures and bus information to initialize.

System software component is detected in the main GPS information to determine the current location of the bus, and then decide whether to play voice messages. Also need to implement the key features required, such as broadcast and so switch to manual. Part of the system software development work is based on the Linux development environment to achieve. According to the system to complete the function and operation of each module, the main program is partly based on multi-threading and message queue, it can be timely to receive GPS data.

GPRMC frames because the data only, serial communications is not the amount of data, communications and faster data processing, the system can promptly report broadcast stations and other audio information. Buses passing the latitude and longitude data needs of each site pre-measured, and stored into the system data area, as a comparison reference. GPRS transmission of information through the serial port using the inquiry method, the key is also used to receive inquiries conducted to determine which function key pressed. Software using C language, debugging successful burn to Flash, for offline operation.

2. 2 GPS Module

GPS module settings due to the power-down loss, both at each system startup to initialize the GPS module. Output of the module is set to a second GPS information.

System startup, the module receives GPS information, and then parse out the GPS information, according to analysis from the latitude and longitude information and data area of ??the site information stored in comparison to calculate the actual distance. If the distance to threshold, the start-stop GPS interrupt. The GPS module receiver module

follow the NMEA. 0183 agreement, to frame a variety of formats, are "MYM" the beginning. Output data is in ASCII character code, the content includes latitude, longitude, speed, date, heading and satellite status information. More than 10 frame format, the system uses positioning data is limited to $ GPRMC frame format.

The system boots, GPS module via the serial port on the set of real-time ask for much because the system will be set to the second output of a GPS RMC data. The idea is to extract the GPRMC statement to set up a data buffer, the received GPS data into the buffer, the buffer is full when the time to find it in the buffer received GPRMC positioning statement, and if you do not receive re receiving GPS data. If you find a GPRMC positioning statement is the statement in the need to determine the location of the buffer maximum number of bytes from the buffer is greater than 62 bytes (because the program needs GPRMC positioning statement, number of bytes contained in 62), and then through a multi-program to extract the relevant latitude and longitude, time and speed information and related data processing thread processing. Work flow system shown in Figure 3.

Figure 3 system workflow

2. 3 GPRS wireless communication module

GSM module embedded as TCP / IP protocol, you can directly call the AT commands to the server via TCP, UDP communication. Wireless communication is divided into upstream data conversion module and communication module 2 modules.

Uplink data transfer modules main function is to receive the GPS data or status information related to data format into an appointment in order to communicate with the main information center. The module will determine the need to convert the data is GPS data or information or status information related to both have, and then select the appropriate conversion process. Can see from the above description of the GPS data is received the order stored in the data buffer which, and what data is to extract the corresponding position in the buffer on it. Data is stored in character form, so the actual use when the data must be converted into plastic surgery.

Downlink data conversion module into the module features and functions upstream Instead, it sends the command to the main information center to identify and send to the car terminal, and notifies the user interface module displays.

Communication modules main task is to complete vehicle terminal with the monitoring center of the communication, both through the GPRS networks and the main information center for wireless communications. If the vehicle terminal and host computer is far away across the GPRS network can be directly connected with the monitoring center, and the GPRS network through SIM548C modules connected with the monitoring center is also very convenient, just a few to the GPRS module AT command to send , but the control center must have a fixed Internet IP. Launch vehicle terminal while SIM548C module will also be launched, this is the module connected to the GPRS network will automatically enter the command mode. After successful dial-up connection on the GPRS network to, and then the serial port module is connected with the SIM548C read and write operations can be achieved with the monitoring center of wireless communications.

Found in the test, due to differences in the wireless signal, network signal is poor in some places is easy with the main information center lost Internet connection. To solve this problem, the use of multiple threads in the system to monitor the network connection status, once lost network connection, and immediately re-connected with the main information center.

2. 4 voice playback module

Philips SPI interface, with voice playback audio chip, driver for the sound card under Linux devices. By S3C2410 SPI control audio chip, audio data transmitted through IIS, and ultimately drive the audio chip card into a system of standard equipment.

Reporting stations in the voice, the need for buses to deliver voice signals the speaker, power amplifier circuit MAXIM amplifier module, the power amplifier module using a single-ended input mode, enter the negative terminal directly to ground. The amplifier module

mono / stereo, D audio power amplifier can deliver up to 8 stereo load 2 21W power, or to load up to 4 mono 1 42 W power, efficiency up to 87%. Class D amplifier module combines the efficiency of the amplifier and Class AB amplifier performance without bulky heat sink, reducing power consumption. The power amplifier module uses + 10 ~ + 18 V single power supply, the load can be driven BTL configuration.

Used to play the stops, advertising and information, and voice of the player selection of players based on open source in the source code changes based on the form for broadcast short audio playback thread, audio playback function for the system decency.

2. 5 display button module

Screen keyboard scanning and data processing done by the MCU 51. Main achieved

keyboard keyboard scan display panel, LCD screen display and to communicate with the ARM processor module.

Display button module serial port communications and data processing module, the scan button to send the data processing module for processing, while data processing module receiving display data command, in the corresponding position of the LCD screen display data, in order to achieve the stops car function of human-computer interaction systems to achieve the bus scheduling management.

GPS and GPRS-based automatic station bus system, a positioning function, GPRS wireless communication capabilities, to achieve automatic station, scheduling, messaging and communications center, with a USB interface, and so on.

Greatly reduce the labor intensity of public transportation employees, improve the scientific management of the bus.

3 Conclusion

Bus station system of Intelligent Vehicle GPS positioning technology using GPS, wireless communication technology, with a small, broadcast accurate and so on.

To achieve automatic station, scheduling, messaging and central communications and other functions. Through the USB interface to enable the system stores multiple lines to facilitate the temporary replacement buses operating lines; such as the use of radio buttons and interactive interface to facilitate passengers to receive relevant information; can provide advertising and other value-added services. System to establish a complete management system for intelligent traffic scheduling provides a key transit vehicle systems.

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