VISA Interface Library

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Inhaltsverzeichnis 1 Introduction 2 Usage 3 Resource Manager Functions and Operations 4 Resource Template Operations 5 Basic I/O Operations

Introduction

This VISA Library contains function blocks to access lab equipment via the VISA (Virtual Software Architecture) interface.

The main objective of the VXIplug&play Systems Alliance is to increase ease of use for end users through open, multi-vendor systems. The alliance members share a common vision for multivendor systems architecture, encompassing both hardware and software. This common vision enables the members to work together to define and implement standards for system-level issues.

As a step toward industry-wide software compatibility, the alliance developed one specification for I/O software—the Virtual Instrument System Architecture, or VISA. The VISA specification defines a next-generation I/O software standard not only for VXI, but also for GPIB, Serial, and other interfaces. With the VISA standard endorsed by more than 35 of the largest instrumentation companies in the industry including Tektronix, Hewlett-Packard, and National Instruments, VISA unifies the industry to make software interoperable, reusable, and able to stand the test of time. The alliance also grouped the most popular operating systems, application development environments, and programming languages into distinct frameworks and defined in-depth specifications to guarantee interoperability of components within each framework.

Usage

To use NI-VISA, you need the following:

• Appropriate hardware, in the form of a National Instruments GPIB, GPIB-VXI, MXI/VXI or serial interface board. For other hardware interfaces, the computer's standard ports should be sufficient for most applications.

• For GPIB applications, install NI-488.2. For VXI applications, install NI-VXI. For other hardware interfaces, NI-VISA uses the system's standard drivers.

• NI-VISA distribution media

• If you have a GPIB-VXI command module from another vendor, you need that vendor's GPIB-VXI VISA component. It will be installed into the <VXIPNPPATH>\<Framework>\bin directory. For example, the Hewlett-Packard component for the HPE1406 would be: "C:\Program Files\IVI Foundation\VISA\WinNT\bin\HPGPVX32.dll".

More Info:

• http://www.ni.com/visa/
• http://www.ivifoundation.org/

Resource Manager Functions and Operations

• VISA [ Open Interface ]
  Opens a session to the specified device using viOpenDefaultRM and viOpen
• VISA [ viOpen ]
  The viOpen() operation opens a session to the specified resource.
• VISA [ viOpenDefaultRM ]
  The viOpenDefaultRM() function must be called before any VISA operations can be invoked.

Resource Template Operations

• VISA [ viClose ]
  The viClose() operation closes a session, event, or a find list.
• VISA [ viGetAttribute ]
  The viGetAttribute() operation is used to retrieve the state of an attribute for the specified session, event, or find list.
• VISA [ viSetAttribute ]
  The viSetAttribute() operation is used to modify the state of an attribute for the specified object.

Basic I/O Operations

• VISA [ viWrite ]
  The viWrite() operation synchronously transfers data.
• VISA [ viRead ]
  The viRead() operation synchronously transfers data.
• VISA [ Query ]
  Send a command and wait for the response using viWrite and viRead.

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