This article refers to the address: http://
introductionIn recent years, the rapid development of electronic technology has made PDA, MP4, high-end mobile phones and other electronic products have entered the lives of ordinary people. People are increasingly demanding these products, and implementing GPS satellite navigation on the MP4 allows the holder to enjoy a more useful function in addition to entertainment functions such as music, pictures, movies, network communication, and mail. By embedding the GPS (Global Position System) navigation system into the MP4, traffic navigation, satellite positioning, ephemeris time can be achieved, or it can be placed in the vehicle for car navigation, and the palm can be provided to the traveller. Electronic maps, etc. This paper takes a MP4 (Avisco AV700) from a French company as the prototype to illustrate the system principle, structure, software modular design and implementation process of embedding the GPS navigation system into the MP4 hardware platform.
1 system hardware requirements
The core chip TMS320DM270 in the AV700 MP4 is a dual-core architecture based on a multi-processor architecture with integrated DSP and ARM7RISC processors. Among them, the 80MHz ARM7TDMI 32-bit RISC microcontroller is the main Controller of the whole system. To meet the processing needs of the control and interface. The controller has a level 1 cache (8 Kbytes) and on-chip program/data memory (32K bytes). TI's 90 MHz DSP chip programmable TMS320C54XTM features on-chip program/data memory (128 Kbytes) for Process audio encoding and decoding.
The TMS320DM270 integrates a programmable coprocessor specifically for high computational requirements, where the SIMD Image Processing Engine (iMX) performs motion estimation and compensation in DCT, inverse DCT, and many other processing operations. Other coprocessors perform variable length encoding/decoding, quantization and inverse quantization, and the like.
The device features a preview engine for real-time viewing and digital zoom, a hardware pixel preprocessor for DSC systems, an integrated multi-screen display (OSD), a color LCD digital interface, and supports up to 64MB and 32/16 bits. Interface 120MHz SDRAM, 10-bit DAC for NTSC/PAL mixed video output, 8/16-bit digital RGB/YUV output, serial audio codec interface (McBSP), USB1.1 function controller device, etc. In addition, ARM7 There is also a JTAG interface and a fully functional debugging tool. TMS320DM270 can meet the needs of embedding CPS navigation functions into MP4 devices with its powerful processing capability and multimedia performance.
In summary, the implementation of the GPS navigation system with an embedded system is a good choice. The core chip of the AV700 is the TMS320DM270 application processor, supplemented by certain external devices to form a fully functional system.
2 GPS system principle and structure
The entire GPS system consists of three parts: the South Space Satellite, the GPS module and the user equipment. The space part is the GPS satellite group, which consists of 21 positioning satellites and 3 backup satellites. These satellites can cover the whole world, so that any satellite on the earth can receive satellite signals of 4 stars, thus achieving three-dimensional positioning and speed measurement. The GPS module part receives the satellite signal and separates the latitude, longitude, altitude, speed and time by modulation, and finally sends it to the digital processing chip through the serial port for processing. The user equipment realizes its own positioning by receiving satellite signals, and implements road sign indication through an electronic navigation map pre-installed in the chip to guide the user to the destination.
Figure 1 shows a block diagram of the overall structure of a GPS navigation system. The user equipment part has the following Components: a GPS receiving module, a digital signal processing module, a key input module, a liquid crystal screen and an audio output module.
The core hardware circuit module is composed of TMS320DM270 processor and necessary additional equipment. Its structure is shown in Figure 2. The memory uses 64 MB of SDRAM. To ensure that the computational space is large enough, the system is also configured with 64 MB of flash memory for storing operating systems, applications, and data. In addition, the relevant interface circuit is also configured.
The GPS module communicates with the TMS320DM270 via a serial port (U-ATR). Since the GPS navigation system is embedded in the MP4, the positioning navigation function only adds an auxiliary function of the MP4. Therefore, the system inputs the keyboard signal by expanding the button to control the switching of the MP4 function.
The software can be developed on the host and then downloaded to the system via the USB interface.
3 software module design and development
The software design module of this system is shown in Figure 3. The software is centered on an electronic map analysis module and database, including GPS modules, communication modules, and display and sound output modules.
Various geographic information and data are recorded in the database. In fact, the entire city can be seen as a directed graph with nodes and turning points as nodes. Each road segment can be represented by a broken line segment, and the latitude and longitude coordinates of each turning point can be set, and then a certain "attribute field" is assigned. When the MP4 is turned on and in the GPS receiving state, the system will receive and analyze the satellite signals by the GPS module, and calculate the current values ​​of latitude, longitude, speed, direction, etc., to obtain the current position of the MP4 holder on the electronic map. If the position movement can be recorded regularly, an intuitive running route can be displayed on the LCD. In addition, accurate ephemeris time can be obtained to provide great convenience for travel and tourism.
For the navigation system software, considering that uCLinux has been adopted in more than 90% of MP4, and the open nature of uCLinux makes a large part of the software can be transplanted free of charge, which can save a lot of licensing fees, many Lin-ux masters Very rich application packages have also been developed, such as web browsing, email, games, personal transactions, and even GPS electronic maps. If you can get their support, you can save a lot of development time. So this design uses uCLinux as the operating system and Hitool for uCLilux as the software development tool. The development process is shown in Figure 4.
Hitool for uCLinux is a development kit of Hitool System. The whole development process can be completed in Windows environment and debugged by JTAC. This way you can debug the kernel and drivers, as well as debug your application. After the hardware platform (based on the ARM7 processor) is established, the prepared uCLinux kernel (linux.elf) can be downloaded to the RAM through the emulator. You can debug the Linux kernel just like debugging a normal embedded program, then compile and generate the "fit" operating platform (linux_bootrom.bin), and finally burn it into Flash.
After the system software is compiled, the compiled software can be downloaded to the file of the target board through the USB port. After debugging and running normally, you can put it into trial and develop new functions.
4 Conclusion
GPS is the most widely used navigation and positioning system in the world. Whether in car navigation systems or handheld navigation devices, especially in PDAs, MP4s, high-end mobile phones and other electronic products, high-speed processors and powerful multimedia functions are used to implement satellites. Navigation has its vast development space.
Roller Blinds Accessories,Window Covering Accessories,Accessories For Blinds
Ruixiang M&E Co., Ltd. , http://www.gzcurtainmotor.com