Research And Development Of Digital Image Capture And Sending Unit

Along with the high-speed development of computer technology,embedded system rise rapidly because of its advantages of portability,low power consumption,low-calorie and noiseless,which PC cannot match. With the work frequency of the embedded ASIC increaseing,functions which it can achieve are growing stronger and stronger,and the performance gap between the PC is reduced rapidly,it is playing an increasingly important role in many fields,such as engineering control,consumer electronics,image processing,network transmission,etc.Based on embedded system developing platform for Linux,combined with the development direction of embedded system and wireless network,I designed this image capture and wireless transmission unit.This unit's main funtion is capture image data from USB camera and transmit these data through wireless LAN.The thesis mainly includes hardware development board with the module design,how to build the embedded development environment,and the design of the software for PC which can capture image and transmit the data,etc,and focuses on the transplant of the diver for wireless network card,the configuration of the wireless network card,the method of image capture and display,and how to tramsmit image data. Apart form the introduction of the research method and process,but also discussed lots of difficult issues,and gives a detailed implementation steps,such as the transplant of wireless network driver,the implementation of image capture through V4L method,libjpeg library revisions,etc.The system is designed to achieve three functions: video broadcasting function based on ARM, video interactive function based on ARM and video broadcast function based on PC. Video broadcasting function based on ARM is that one arm terminal captures the image from camera,and then sends it to the wireless network,other treminals receives the image,decompress it and display on the screen. Video interactive function based on ARM is that two terminals capture image,and then send it to each other,after received the image sent by the other, decompress it and display on the screen.Video broadcasting function based on PC is that capture the screen image of PC ny software and then send the image to the wireless network,other treminals receives the image,decompress it and display on the screen.The system's hardware circuit is based on ARM9 S3C2440A chip,the external circuits connected to it is the 64M SDRAM(for running the program), 64M Nand Flash (for storing the program), SD card(for storing the pictures), serial port(for outputing the debug information), LCD screen(for displaying images), JTAG(for burning the Uboot), and two USB ports (connected to a USB camera and a USB wireless network card). This paper focuses on system software design,which includes two parts:ARM embedded software design and PC software design.The ARM software design includes the Uboot transplantation, Linux kernel transplantation, driver transplantation of wireless network card, configuration of camera driver, transplantation of iwconfig which is the wireless card configuration tool in Linux, transplantation of libjpeg which is a JPEG image decompression library, and application's writing and debugging. System uses iwconfig tool to configurate the wireless card works in the peer mode, that is the ad-hoc mode, in this mode, the terminals can create a network by not using the wireless network router. In order to avoid the interference between sub-networks,we separate the network from other networks by configuring the wireless card's network name and encryption key. The video transmission module of application is written separately, it includes image capturing and sending function,and image receiving and display function,it can sending and receiving image at the same time by using multithread technique. System uses the UDP network transport protocol, it has good real-time feature and it's easy to use. In addition to the video transmission modules,the PC software design also used the shortcut keys and keyboard hooks etc, so users can run the program by just using the keyboard.The unit successfully achieved on the wireless network card and the camera driver,by configurating the wireless network card parameters such as work mode,the terminal can build a group network in the absense of other wireless routing devices,and on this basis to achieve the image data capture and transmission.After long-running experiment,the system's wireless network is stable and reliable,the transmissin speed is good,data integrity is guaranteed basicly,so that the image shows no loss.