A virtual instrument bus using network programming

This paper provides an overview of a virtual instrument bus created at the University of Maine Orono. Software to support automated tests has become difficult to maintain as the number of test boards and test instruments grows. A variety of test instruments such as logic analyzers, signal generators, and data caches connect and communicate to workstations using a General Purpose Interface Bus (GPIB). This paper describes two software packages. The first is a "virtual instrument bus" that makes a large number of GPIB buses on separate networked computers appear to be on a single bus. The second is an object-oriented instrument library. The library is designed to support a variety of instruments using a common framework in an easily maintained software package. The virtual instrument library is developed using remote procedure calls (RPC). All workstations supporting an instrument bus run a background program called a Bus Server that handles bus communications and provides an interface to the computer network. Communication to the various Bus Servers is handled by the Virtual Bus Library. This interface makes the physical configuration of the instrument buses transparent to the software developer. The virtual bus software provides easy code reuse for quick program generation used for automated testing, at the same time making all instruments appear to be located on one single bus.