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Logistics based on GPS + CDMA terminal design vehicle monitoring

In Electronic Infomation Category: L | on April 15,2011

With the national economy, the continuous development of transport, logistics and TC74LCX07FT datasheet and transport industry has become essential to promote rapid economic development of basic industries. Although various types of logistics and TC74LCX07FT price and transport, warehousing enterprises in the long process of development has accumulated a wealth of practical experience, but the vehicle real-time monitoring of dynamic information has not been perfect solution, for example, feedback is not timely, inaccurate, incomplete and TC74LCX07FT suppliers and other issues led to the capacity of the large number of waste and operating costs high. Vehicles using GPS on the logistics and logistics management control has become the object trends.

Response to these circumstances, the paper studies the logistics vehicle monitoring terminal is proposed based on GPS + GIS + CDMA in the overall system architecture. System global positioning system (Global Position-ing System, GPS), geographic information systems (Geographic Information System, GIS) and CDMA (Code Division Multiple Access) wireless communication technology and into the one.

This design logistics and transport vehicle monitoring terminal, the vehicle through the GPS satellite positioning to obtain the latitude and longitude and other information, after a CDMA wireless communication network to communicate with the monitoring center, the transport vehicles in real-time transmission to the monitoring center all kinds of information for monitoring center to display the whole fleet, query, scheduling.

1 system design

GPS and CDMA-based vehicle monitoring system of logistics and transport terminals by the vehicle monitoring, data transmission networks, and monitoring centers. Where the data transmission network composed by the CDMA network and the Internet.

Through the GPS satellite network, the vehicle terminal can be the object of logistics vehicles and logistics for precise positioning, the CDMA wireless network access Internet link to the monitoring center server, real-time transmission of logistics vehicles to the monitoring center latitude and longitude, speed, heading, altitude, time GPS data, the monitoring center can have a geographic information processing and inquiry function of the electronic map display, vehicle for all kinds of information, real-time monitoring of vehicles running.

Another monitoring center also has a communication function with the vehicle terminal, logistics transport vehicles to real-time scheduling, timely handling of incidents for a variety of logistics and transportation fields.

2 terminal hardware design

This vehicle terminal hardware design of the logistics structure from S3C2440A, JTAG on-chip debug interface, video interface, audio interface, reset circuit, CDMA wireless communication module, GPS module, power supply circuits, LCD touch screen, keyboard and other components, external SDRAM, NAND FLASH, NOR FLASH as an external memory, the hardware structure shown in Figure 1.


Figure 1 terminal hardware design hardware

2.1 CPU Selection

System to meet real-time, large amounts of data processing, GPS signal reception, CDMA data transmission, and other requirements, end-use Samsung S3C2440A 32 Wei ARM chip as the CPU. S3C2440A using advanced ARM920T core, on-chip integrated 3-way UART serial ports, 2 SPI ports, 8-channel 10-bit ADC, with a calendar function of RTC, with the PLL-chip clock generator, 130 general-purpose I / O port, 24 external interrupt sources and other rich resources, ease of development, is a very high cost-effective chip.

2.2 CDMA Module Interface Design

Terminal module with a Huawei EM200 CDMA1X. The module is working band is 800 MHz, the maximum transmit power is 0.25 W, receiver sensitivity is less than -106 dBm, operating voltage 3.3 ~ 4.2 V, integrated UART, UIM cards, antennas and other rich resources interface. Supports the standard AT command set. Operating temperature limit of -30 ~ +75 , operating temperature range, suitable for a variety of logistics and transport environment.

S3C2440A has 3 UART serial port, EM200 S3C2440A module connected through the serial port 1, as both inputs and outputs are TTL level, so no level conversion can be directly connected to the data which is sent EM200 pin end, and S3C2440A the RXD terminal is connected; EM200 pin is the data receiver, the TXD terminal connected with the S3C2440A, which implements the send and receive data between the two. Huawei EM200 CDMA1X S3C2440A module connection diagram shown in Figure 2.


Figure 2 Huawei EM200 CDMA1X S3C2440A module connection diagram

S3C2440 which the TXD0, nRTS0, DTR pin, respectively, after 3 1 k resistor is connected with the EM200s feet, to prevent excessive current to the chip damage.

2.3 GPS Module Interface Design

GPS precise positioning module is the key to the terminal, the terminal design is the core, so the terminal selected Gstars SIFEIII behalf GS-15B module.

GS-15B is a high performance, low-power intelligent satellite receiver module. It uses Taiwans MediaTek Inc. is designed MT3329F GPS receiver chip, is a complete GPS receiver. At the same time have the full range of capabilities, to meet the stringent requirements of professional orientation and industrial needs. Built-in GPS antenna, using MTK high sensitivity, low power consumption chip MT3 329F. With fast positioning and tracking 32 satellites. Ultra-small, chip built-in 200 000. Arithmetic unit, a substantial increase in the satellite signal search and computing capabilities. Support NMEA-0183 v2.2 version of the output specifications. Receiver sensitivity of -157 dBm, the operating temperature is -40 ~ 85 , TTL level output voltage 3.3 ~ 5.0 V, cold start acquisition time of only 42 s, the average positioning accuracy of 10 ~ 15 m. Only meet the needs of end-to-cost-effective, but also to meet the demand for precise positioning of the terminal.

S3C2440A and GS-15B of the interface shown in Figure 3. Terminal 2 is connected serial port using the S3C2440A GPS module, in order to enhance the driving capability, the S3C2440A the TXD1 and PXD1 added a 2 pin 100 k pull-up resistor. GPS terminal receives only general information on GPS do not write, so in order to protect the chip, the S3C2440A the RXD1 between the GS-15B with the addition of a 100 resistor and a model for the MCIA148 reverse diode, thus ensuring the terminal run-time stability.


Figure 3 S3C2440A and GS-15B interface connection diagram

3 Terminal Software Design

Part of the terminals software is based on WinCE 5.0 embedded operating system design, WinCE is a multi-tasking, fully preemptive 32-bit embedded operating system that supports WinCE MFC, ATL, WinCE API and some additional programming interface and various communication technologies. WinCE embedded operating system has a good user interface, real-time high, less resource, development tools, rich and strong technical support and other advantages, to fully meet the design requirements of the terminal software.

3.1 Terminal software design process

First system power on, start the bootloader, load WinCE kernel, boot WinCE embedded operating system. Then initialize the CPU, LCD, GPS, CDMA and other peripheral modules, then load the serial driver and network protocol, if the load is successful implementation of user applications, if the load fails to return, re-load the serial drivers and network protocols. End-user applications which include: CDMA wireless network access procedures, network data transmission process, GPS receiver program and so on. Terminal software design flow shown in Figure 4.


software design flow chart Figure 4 Terminal

3.2 CDMA wireless network access program

CDMA terminal through AT command control module, wireless Internet access and network data transmission.

System is running, the first CDMA module initialization, set the baud rate to 115 200 b / s, and then enter the dial-up wait state, the terminal through the PPP dial-up connection logon to the network, the access number is 777, the user name and password are card. Confirm the success of landing the network, the GPS receiver program calls and network data transfer procedure for the regular way to the monitoring center to send GPS location information terminal.

Establish PPP (point-to-point protocol) connection of AT commands and return values ??are as follows:


3.3 CDMA wireless network communication program

CDMA network access terminal through the Internet, the wireless network communication program will parse the GPS data terminal uploaded to the monitoring center through the Intemet. The format of the terminal software design flow for network socket communication, corresponding to the TCP / IP protocol in the TCP connection-oriented protocol. Network data transfer program client / server system programming, the terminal (client) process manipulated by the user; and control center (server) process resides in the continuous operation of the host, waiting to enter the terminal connection request.

Monitoring center network communication program flow is as follows: 1) socket () function creates a socket and socket address structure to the assignment; 2) bind () function to set the interface with the local IP address, end * binding , use a static IP address; 3) listen () function on the socket * connection request; 4) accept () function, the connection request receiving terminal to generate a new set of interfaces, and describes the characters and the terminal connections, the use of new socket send and receive data; 5) with the fork () function derived from the new child process and terminal communications, the parent process to continue * other requests. This would avoid a terminal with the monitoring center to establish a connection, the monitoring center can no longer communicate with the other end the problem. TCP

terminal program flow is as follows: 1) socket () creates a local socket, to the monitoring center socket address structure assignment; 2) connect () function, the local socket socket to the monitoring center to establish a connection unsolicited request, the three-way handshake to establish TCP connection; 3) If the connection is established, then use the send () and recv () function with the control center communications; 4) end of the communication with the close () close the socket.

3.4 GPS serial terminal program

Software development tools using EVC (embedded visual C + +), EVC is the mainstream on the Windows CE development tools, encapsulates the underlying communications network, COM interop, RAPI and so on. EVC supports a subset of MFC class library, so that on the Win32 platform, VC program can be easily ported to WinCE platform. GPS serial port terminal program

to complete two major functions: to receive GPS data and GPS data analysis. GPS module output follows the NMEA-0183 standard. Program flow is as follows:

1) using the OpenPort () function to open serial port, the function used to create file function CreatFile () to open the serial port 2, port 2 for the operation of the handle m_hComm;

2) If the serial port 2 opened successfully, read the current serial port settings, namely, by GetCommState () reads the serial port parameters DCB structure variable;

3) with SetCommState () 2, corresponding to the serial port settings: If set the baud rate is 4 800 b / s, 8 data bits, no parity, 1 stop bit, no flow control; < / P>

4) by-bit read data, to determine whether the frame starting $ GPRMC, if it is extracted for the $ GPRMC time, longitude, latitude, speed, and other information stored in the corresponding structure; to determine whether the frame starting $ GPGGA If the $ GPGGA 9 from the field and into the corresponding elevation extraction structure; to determine whether the frame starting $ GPGSV, if the $ GPGSV number of satellites is to extract the effective, efficient, and the satellite number and other information into the appropriate structure ;

5) with SetWindowText () in the LCD display on the GPS receiver to the GPS data and the parsed information;

6) Finally, when required by ClosePort () function to close the serial port 2. The function uses CloseHandh () Close the handle to the serial port 2 m_hComm.

4 operating results

This terminal software designed to run shown in Figure 5. GPS data terminal, including UTC time, latitude and longitude, ephemeris, direction, altitude and so on. Achieve a comprehensive and visually display the GPS data, function, style with a friendly interface. Which Figure 5 (a) of the GPS serial port can be configured to receive and display the original NEMA-0183 statement. Figure 5 (b) latitude and longitude in the Beichen District in the New Campus of Hebei University of Technology measured, accurate to the second level, longitude as longitude 117 4134 .4 ", latitude N 39 376 .2". Test time is June 6, 2010, afternoon 16:24:22.


Figure 5 GPS data terminal interface

Tests show that the terminal software can run smoothly on WinCE 5.0 embedded systems, real time and with good accuracy.

In addition, the terminal through a CDMA wireless communication network in real time GPS positioning data to the monitoring center, monitoring center that is real-time electronic map display terminal location. After testing, the actual location of the terminal position on the electronic map in full compliance with, and has good real-time data refresh time is less than 3 s, GPS position drift is less than 20 m.

5 Conclusion

For the rapid development of Chinas logistics industry background, the paper and CDMA-based GPS vehicle monitoring terminal logistics hardware and software design. Implementation of logistics vehicles to remotely monitor and real-time scheduling. Compared to traditional vehicle terminal, this design uses 32-bit ARM processor with a faster processing speed, greater storage space and more intuitive interface displays and so on. Especially in the GPS data transmission using the CDMA wireless wireless communication technology, GPRS technology is more suitable than the traditional long-distance, large amount of data requires a very high real-time vehicle terminal area. With the development of 3G mobile communication systems, GPS uses CDMA network to the 3G network terminal more easily smooth transition, there will be a broader application.

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