Study And Implementation Of LXI Bus VISA DLL Based On Software Reuse

With the rapid development of automatic test technology, the application of virtual instrument becomes more and more extensive. Virtual Instrument Software Architecture (VISA) is a collection of the standardized I/O function library and its correlative criterion, and is the software connection between computer and instrument. In the specified hardware system, the improvement of performance and development efficiency of automatic test system depend on the design of VISA. By the use of the high-efficient and reliable VISA function library, the development time and development consumption of the virtual instrument software can be reduced and the software is scalable.Due to the new interface test equipment, the drivers need to be rewritten by developers in the design course of the VISA function library. When the interface is extended, the neglect of the interface commonness will lead to low development efficiency and heavy workload, and the measure of multi-buses instruments is impacted. Therefore, on the basis of software reuse, this paper establishes the DSSA common property model of VISA function in the automatic test field and designs the VISA standard I/O function library by researching the VISA standard and the software development method. Otherwise, it extends the LXI interface of instrument on the basis of GPIB and RS-232C interfaces. The specific tasks are as follows:1. The LXI bus standard and its three mechanisms:configuration mechanism, discovery mechanism and trigger mechanism were researched.2. The structural-level and functional characteristic of I/O function library were deeply analyzed, and the VISA function library was designed which used the software reuse method based on component and dynamic link library. At the same time, this method was compared with the traditional design method to prove its efficiency.3. By analyzing the similarities and differences of automatic test system based on GPIB, RS-232C, LXI interface in the field of instrument measure, function model and DSSA model were established, then, the reusable component of LXI automatic test system was designed and developed.4. The functional characteristic of VISA standard function was discussed and researched, and the developed component was reconstructed. The LXI interface of instrument was extended on the basis of GPIB and RS-232C interfaces, and the VISA function library was written which included resource management class function, basic I/O class function, formatted I/O class function, VISA control and management class function. This VISA function library was tested and debugged in the multi-buses automatic test system and the dynamic link library was created.5. The control center application program was designed and written based on VC++ language platform, and the VISA dynamic link library was utilized in the LXI-bus digital multi-meter remote test system to verify its feasibility and effectiveness. At the same time, the measure data was saved by using EXCEL automation technology.