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VISA Overview

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What Is VISA? Interfaces Used with VISA Supported Vendor and Resource Names

What Is VISA?

Virtual Instrument Standard Architecture (VISA) is a standard defined by Agilent Technologies and National Instruments for communicating with instruments regardless of the interface.

The Instrument Control Toolbox software supports the GPIB, VXI, GPIB-VXI, TCP/IP, USB, RSIB, and serial port interfaces using the VISA standard. Communication is established through a VISA instrument object, which you create in the MATLAB workspace. For example, a VISA-GPIB object allows you to use the VISA standard to communicate with an instrument that possesses a GPIB interface.

Note   Most features associated with VISA instrument objects are identical to the features associated with GPIB and serial port objects. Therefore, this chapter presents only interface-specific functions and properties. For example, register-based communication is discussed for VISA-VXI objects, but message-based communication is not discussed as this topic is covered elsewhere in this guide.

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Interfaces Used with VISA

For many VISA applications, you can communicate with your instrument without detailed knowledge of how the interface works. In this case, you might want to begin with one of these topics:

• Working with the GPIB Interface

• Working with the VXI Interface

• Working with the GPIB-VXI Interface

• Working with the Serial Port Interface

• Working with the USB Interface

• Working with the TCP/IP Interface

• Working with the RSIB Interface

If you want a high-level description of all the steps you are likely to take when communicating with your instrument, refer to Instrument Control Session.

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Supported Vendor and Resource Names

When you use instrhwinfo to find commands to configure the interface objects, you must use valid vendor or resource names. The supported values for vendor are given below.

Vendor	Description
agilent	Agilent Technologies VISA
ni	National Instruments VISA
tek	Tektronix VISA

The format for rsrcname is given below for the supported VISA interfaces. The values indicated by brackets are optional. You can use the instrument's VISA Alias for rsrcname.

Interface	Resource Name
GPIB	GPIB[board]::primary_address[::secondary_address]::INSTR
GPIB-VXI	GPIB-VXI[chassis]::VXI_logical_address::INSTR
RSIB	RSIB::remote_host::INSTR (provided by NI VISA only)
Serial	ASRL[port_number]::INSTR
TCPIP	TCPIP[board]::remote_host[::lan_device_name]::INSTR
USB	USB[board]::manid::model_code::serial_No[::interface_No]::INSTR
VXI	VXI[chassis]::VXI_logical_address::INSTR

The rsrcname parameters are described below.

Parameter	Description
board	Board index (optional — defaults to 0)
chassis	VXI chassis index (optional — defaults to 0)
interface_No	USB interface
lan_device_name	Local Area Network (LAN) device name (optional — defaults to inst0)
manid	Manufacturer ID of the USB instrument
model_code	Model code for the USB instrument
port_number	Serial port number (optional — defaults to 1)
primary_address	Primary address of the GPIB instrument
remote_host	Host name or IP address of the instrument
secondary_address	Secondary address of the GPIB instrument (optional — defaults to 0)
serial_No	Index of the instrument on the USB hub
VXI_logical_address	Logical address of the VXI instrument

obj = visa('vendor','rsrcname','PropertyName',PropertyValue,...) creates the VISA object with the specified property names and property values. If an invalid property name or property value is specified, an error is returned and the VISA object is not created.

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Controlling Instruments Using VISA

Working with the GPIB Interface

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