Design And Implementation Of Virtual Instrument System Based On USB Bus

The innovation of equipment is promoted by computer and informationtechnology. From the earliest analog instrument to digital instrument, the time ofvirtual instrument comes after the revolution of intelligent instrument. In theearly time, GPIB, RS232and PCI interface were used usually. As the limitationsof electrical characteristics and design principles, installation and application areinconveniences which affect the flexibility of virtual instrument directly.However, the emergence of USB bus technology can solve the problem ofinterface limitation. Based on this idea, a general virtual instrument using theUSB bus was designed in this paper.The development process and research status of the virtual instrument weredescribed firstly. And the USB bus protocol and technical superiority were alsointroduced. Hardware and software system were designed in line with the USBprotocol. Hardware system mainly consists of the selection of the chip, FPGAfirmware, data acquisition module, USB communication interface module, andpower supply circuit. The hardware system which can accomplish the acquisitionand transmission of data is an acquisition system based on FPGA; Softwaresystem including USB drivers, firmware, and LabVIEW virtual instruments.USB firmware developed in Keil3environment is the focus of this paper whichcan ensure USB bus works in virtual environment with high speed and stabletransmission. USB driver was implemented in the NI-VISA.FPGA was used as a core controller in this system to control A/D converter,send data into the FIFO and transmit data to PC through USB interface. Thecollected signals were displayed and analyzed in the LabVIEW The function ofsignal filtering and spectrum analysis was implementation, and the experimentalresult was given finally.