Usb2.0 Image Capture Card-based Design And Realization

With the development of multimedia technology, the digital image acquisition and processing have become the core and foundation of a lot of application system. In this paper, the design, fabrication and software programming of an image acquisition card which is based on USB2.0 interface are presented. This card will be used for acquiring image data exported by infrared camera in PCB diagnosis system which is based on thermal images processing.The commercially available digital image acquisition cards are expensive, and usually connected through PCI interface, which is not convenient to use. The card we develop can be connected through USB interface providing great convenience to use and take around, and can make a good match with our infrared camera. Interiorly it hasn't been reported to integrate image acquisition card which is based on USB interface with infrared camera.In this dissertation, beginning from the significance of image acquisition and the application background, the modules of the image acquisition system are presented, the capability requiring of every module is analyzed, the existing computer bus technology and programmable logic technology are compared, a scheme is brought forward which uses USB2.0 as the bus interface and uses FPGA to control the logic.The USB2.0 interface has a lot of advantages, including Plug and Play, connecting convenience, high-speed transportation and strong compatibility. It has been widely used in many devices. By using FPGA, the design of logic-control circuit has been significantly simplified, and because of the advantages such as small size, high speed and programmability, FPGA has become the top option in digital logic design.In this dissertation, the method and implementation process of both hardware system and software design are presented. In aspect of hardware circuit, the design of the clock, power and interface is introduced; the start-up configuration modes and the significant signal pins connections are explained; the Slave FIFO interface mode between USB chip and FPGA chip is chosen after analyzing. System software design is composed of three parts: firmware, driver and application. In the part of firmware, software flow and the interrupt system are put emphasis on. Under Windows, the WDM (Win32 Driver Model) driver is the provider of functions, and the operating system is in charge of the process. So after the hierarchy of WDM is introduced, the sequence of function calls and the design method of key functions are analyzed. In Application design, the format conversion and the display usage are focused on.After design, fabrication and debugging, the image acquisition card has been completed, and the anticipated goal has been achieved. It has provided a firm technical basis for miniaturization and practicality of the PCB diagnosis system which is based on thermal image processing.