R&D Of S3C2440A-based Digital Wireless Local Area Network Multimedia Receiver

With the rapid development of Internet, we entered a differente information age. Video, audio and multimedia data communications, as combination of the theme of this era, attract more and more attention by people. More and more wireless LAN devices improve flexibility, especially in the campus, on-demand digital video, classroom management. According this opinion this paper bring up hardware and software solution of digital multimedia receiver based on S3C2440A wireless LAN, and explained the design of hardware and software implementation with the perspective of engineering practice.1. Introduced several key technologies of digital multimedia receiver based on wireless local area network that including the ARM9 core, the 802.11 wireless protocol, video and audio compression algorithms, and validate the technology in the S3C2440A platform applicability.2. Discussed the capabilities of digital multimedia receiver in wireless local area network and determine the need to implement peripherals.3. According to requirements of the digital multimedia receiver in wireless local area network, we determine the need for external hardware devices and configuration of hardware. First, we studied the architecture of ARM9-bus, and then discuss the high-speed memory, the study's NANDFLASH ARM9 controller interface with SDRAM interface, and features of the mechanism, and the corresponding K9F1208 and HY57V561620 hardware connections. Then we introduced special Steppingstone S3C2440A booting mechanism; the liquid crystal display and liquid crystal display interface implementation characteristics and signal interface; the USB bus and Equipment, discussed the expansion of S3C2440A USB bus interface, which uses a USB hub extension GL850G USB interface, and at the same time connect to wireless card RT73 of Ralink and USB video camera base on Vimicro VC0336. In the discussion of button and touch screen, we study the touch screen works and S3C2440A the touch screen controller interface. In the audio input and output, we discuss the audio interface features of S3C2440A, and external audio CODEC chip interface features UDA1341 proposed hardware connection scheme, and subsequently discusses the problem of acoustic echo on hands-free intercom. The acoustic echo problem, and proposed weakening in three kind of method to weak or solve the problem of acoustic echo program, and joined the MSM7731 integrated circuit chip echo cancellation. Finally, we study in three debugging hardware interface: universal serial interface, JTAG interface, network interface, and discussed three kinds of debugging features and hardware interface of their applications.4. Based on the concept of efficiency and consumption, we designed the scheme that making the core board and motherboard PCB separately to improve the success rate. According to the basic principles of PCB designing, we discussed some important point of designing on the core board and the motherboard of the digital media receiver in wireless local area network. The core board includes a number of high-speed devices and high-speed bus, so it is especially important that the simulation before wiring and cabling. We put forward several topology of the high-speed peripheral bus, and make qualitative analysis of the advantages and disadvantages of each topology and determine the high-speed peripheral bus routing strategy. Finally, we have a brief discussion of two layers motherboard production notes and route priority, and some limitations of manufacturing on two layers board.5. We separate software development based on the Linux operating system S3C2440A into three parts: verification of hardware drivers, the set up of platform structures and user applications programing.Verification of hardware drivers is base on RealviewMDK based software development which using ULINK2 as debug tool to achieve high efficiency "none-OS" programming, and to understand the booting, configurtion and running the process on the low level of the ARM9, on the other hand to verify whether the development of PCB hardware works.We separate setting up the platform structures in five hands. Include boot code, configuration and migration, Linux operating system kernel porting, Linux root file system generation, Linux operating system drivers and the preparation of the transplant, the software library migration and configuration. In which the boot code, configuration and migration, we discussed the the necessary conditions of booting Linux kernel, and transport the Linux kernel boot command line of UBOOT boot code. We add the NANDFLASH support in the original boot code of UBOOT and other necessary hardware to modify the software structure such as UBOOT Linux kernel image, root file system and capacity to access the network to download debug image files. Thus we transported in the Linux kernel, the kernel of the Linux2.6.29 version of the basic structure and migration points, and study the method of transplant. Linux root file system, of the Linux kernel file system load at startup, as well as a typical Linux system, the typical root file system of the text, put forward using jaffs2 text file system pointed the root system of production method. In the Linux operating system driver porting and preparation, we set up LCD screen, touch screen, USB wireless network card, USB camera, UDA1341 driver, which focused on explaining the Linux prepared driver structure and the preparation of touch screen driver program structure. In porting in the software and configuration of the library, we ported libjpeg image compression and decompression application library and QT graphics library, and focused on the QT and QT software architecture developed for embedded QT / Embedded.In platform setting up and applications written we discussed the audio and video data stream management architecture, and proposed using message queue process of organization the program each module, and introduces the features of QT developing.6. At last we give a qualitative summary of the digital media receiver in wireless local area network project and put forward some weak porint of architecture on performance, such as the core board wiring problems, bottleneck of USB bus speed, the lack of such floating-point operations, and proposed some solutions.