The Research Of High-Speed Data Acquisition And Transmission System Based On USB2.0

1. IntroductionData Acquisition is the basic means to obtain information, It is a multi-application technology which based on sensor, measurement and signal processing, microcomputer and other technology. At present, the most of Data Acquisition Card connect Personal Computer with inner interface such as ISA and PCI etc. The Data Acquisition Card in PC box vulnerable to the high-frequency signal interference, which lowers the acquisition precision and stability. In addition, they have some defects such as unexpanded, complex etc. Meantime the traditional Data Acquisition Card can not content project on acquisition precision and transmission speed. So now the urgent need for a new type of Data Acquisition Card to meet the needs of practice.The USB Specification was proposed by Intel, Compaq, Microsoft and other companies in 1994, its emergence simplified the connection between PC and PC peripherals, and made PC interface extension to become more easier. It has more advantages than other bus, such as supporting of hot insert & plug, high transmission speed and low expense. Now, USB has been widely used in PC peripherals and it has become one of the best selections in many buses. Especially the 2.0 revision of the USB specification is issued, which is the landmark in the USB history. Its transmission speed is 480Mb/s. So it's possible to realize the high transmission speed between PC and the peripherals.Digital signal processor (DSP) has become an important role in the field of Digital, its designed specifically for the high-speed digital signal processing. DSP is especially suitable for performance image acquisition and processing because of its high speed and Good operational performance.This paper presents and design a high-speed data acquisition and transmission system based on USB2.0. It combines FPGA, DSP and USB technology, Achieved high-speed data acquisition and real-time transmission.2. Research contentIn view of the defect of the existing Data Acquisition System. This paper presents and design a high-speed data acquisition and transmission system based on USB2.0. The system is composed by data acquisition, transmission and pretreatment. After the standard simulation video signal which is exported by CCD camera transforms by video processer, one by one storing in SDRAM one by FPGA. After storing a frame image, inform DSP to read. When DSP receive the signal, read a frame image from SDRAM and process it, at last forward to terminal, waiting for host computer reading request.Base on analyzing the system requirement, this paper design the hardware circuit of high-speed data acquisition and transfer system, and test the system's function. The paper's main study content includes six parts:1. USB protocol analysisIn this part, this paper analyse the USB bus's technical advantage and characteristic, comparing with another buses. I classify the field of application in USB, study the USB bus's communication protocol systemically, and put forward the frame of application system which is based on USB2.0, last introduce the prevalence meaning USB2.0 equipment frame briefly.2. The design of system hardware circuitsIn the design of hardware circuits, this paper design the system hardware circuits based on equipment drawing function. It includes six main parts: data acquisition module, system memory module, FPGA control module, data processing module and system transport module. In order to advance the hardware's image transmission speed, I adopt the DMA mode and PING-PONG memory, which solve the problem of long waiting time of system's read and write sufficiently.3. The development of firmware programThe function of firmware is subsidiary hardware, or control hardware to complete the expectant function. This paper emphases introduces the USB2.0 firmware program, which primary function is response all kinds of host computer's requirement, and dispose hardware or transmit the disposition and revelant data to host computer. In the development of fireware, I use the firmware frame. The main work is completion the equipment initialization, USB equipment request processing, USB hang-up rower processing, customization the USB device descriptor table, and the control of external circuits. The system adopts terminal two block transmission mode, and setup double buffering, which can advance the capability of USB bandwidth, smooth the bandwidth whipping and reduce the waiting time。4. The software development of host computer point The software development of host computer point includes two parts: device driver and user appliacation program. The system's driver is based on the WDM and USB bus interface function. After comprehending the WDM chromatography structure and compose deeply, this paper design the system frame. It is composed by five basic routine: the first is the entry routine for driver, which defines the another useful routine and point to these routines'pointer. The second part is plug and play routine, it's used to complete the equipment state monitor, such as equipment start,stop and delete. The third part is hand out routine, it is used to complete the interaction in application program and equipment, dispose all kinds of I/O request sent by user, and supply the interface for user to control the equipment, such as sent out command of start equipment and begin collection. The forth part is power management routine and unloading routine. The system adopts self-powered mode, and the operation of unit deletion uses the plug and play routine to complete, so these two routines have nothing to do. The application program is directly interactive with user. Application program interviews the driver by calling the Win32 API. The step is calling the CreateFile function to open equipment, after open the equipment, calling the DeviceIoControl function and driver to communicate, reading data from driver. After reading application program , I use C1oseHandle function to close device. The system designs five functions to test the device running.5. The function test and performance analysisTesting the five functions of application program. Though testing, it can get the correct transmitting data. When transmitting data is 307200 byte, the transmission speed can reach 15MB/s. Analysis the factor of possibly influence the transmission speed, present the resolvent. It has the use of reference action to another device development.3. ConclusionIn conclusion, the system applies USB2.0 into high speed image acquisition system, and realize the image high speed acquisition and real time transmission. By testing, the transmission speed can reach 15MB/S. It can read device description mode and collection image data precisely. It solves lots of problems of the traditional data acquisition card, has a widely potential application and use value.