| Visual instrument is a powerful and flexible integrated test, measurement and control system, which is composed of computer technology, application software and modularization hardware. In recent years, Visual instrument develops rapidly and is broadly applied. As a new bus standard in computer peripheral hardware, USB is adopted and widely used in visual instruments for its ease of use, true plug and play, power supply from bus, high transmission speed, etc.Nowadays, USB interface visual instruments in domestic market are mostly developed by using general USB specification. In this way, developing USB visual instruments will expend long time, and interchangeability of products is bad. In order to solve these questions, USB organization issued new class specification-USBTMC (USB Test and Measurement Class) for USB interface instruments. USB visual instrument, which accord with USBTMC specification, will be fully supported by visual instrument software, and users can easily develop instruments driver and application software by using VISA (Visual Instrument Software Architecture) to improve the applicability of instruments on various operating systems.This dissertation analyses the general USB specification, and focus on the research of USBTMC specification. An USB interface data acquisition card is developed, which is consisted of MSP430F169 and PDIUSBD12, and the fireware according with USBTMC specification is programmed. By researching the VISA and its connection method with USBTMC instrument through its common interface functions, a program is developed in Lab VIEW, which can communicate with USBTMC device through NI-VISAWith the rapid development and popularization of network, visual instruments based on network are widely used. After analyzing the structure and character of network-visual instrument, a network-temperature monitor system is built by using the developed USB DAQ card and the net function of Lab VIEW. This system proves the research in this paper.The result of experiments proves that USB data acquisition system based on USBTMC can run normally. For USB visual instrument based on USBTMC, VISA can simplify the programming of software in host; avoid the complex development of driver; improve the software commonability. |
