Instrument Control Toolbox

The GPIB Interface

The GPIB interface is supported through a VISA-GPIB object. The features associated with a VISA-GPIB object are similar to the features associated with a GPIB object. Therefore, only functions and properties that are unique to VISA's GPIB interface are discussed in this section. These unique features are associated with

• Creating a VISA-GPIB object
• The VISA-GPIB address

Refer to Controlling GPIB Instruments to learn about the GPIB interface, writing and reading text and binary data, using events and callbacks, using triggers, and so on.

Note    The VISA-GPIB object does not support the spoll function, or the BusManagementStatus, CompareBits, and HandshakeStatus properties.

Creating a VISA-GPIB Object

You create a VISA-GPIB object with the visa function. Each VISA-GPIB object is associated with

• A GPIB controller installed in your computer
• An instrument with a GPIB interface

visa requires the vendor name and the resource name as input arguments. The vendor name can be agilent, ni, or tek. The resource name consists of the GPIB board index, the instrument primary address, and the instrument secondary address. You can find the VISA-GPIB resource name for a given instrument with the configuration tool provided by your vendor, or with the instrhwinfo function. As described in Configuring Properties During Object Creation, you can also configure properties during object creation.

For example, to create a VISA-GPIB object associated with a National Instruments controller with board index 0, and a Tektronix TDS 210 digital oscilloscope with primary address 1 and secondary address 0:

• vg = visa('ni','GPIB0::1::0::INSTR');
  

The VISA-GPIB object vg now exists in the MATLAB workspace. You can display the class of vg with the whos command.

• whos vg
    Name      Size         Bytes  Class
  
    vg        1x1            636  visa object
  
  Grand total is 14 elements using 636 bytes
  

After you create the VISA-GPIB object, the properties listed below are automatically assigned values. These properties provide descriptive information about the object based on its class type and address information.

Table 4-1: VISA-GPIB Descriptive Properties 

Property Name	Description
Name	Specify a descriptive name for the VISA-GPIB object.
RsrcName	Indicate the resource name for a VISA instrument.
Type	Indicate the object type.

You can display the values of these properties for vg with the get function.

• get(vg,{'Name','RsrcName','Type'})
  ans = 
  'VISA-GPIB0-1'    'GPIB0::1::0::INSTR'    'visa-gpib'
  

The VISA-GPIB Object Display

The VISA-GPIB object provides you with a convenient display that summarizes important address and state information. You can invoke the display summary these three ways:

• Type the VISA-GPIB object at the command line.
• Exclude the semicolon when creating a VISA-GPIB object.
• Exclude the semicolon when configuring properties using the dot notation.

You can also display summary information via the Workspace browser by right-clicking an instrument object and selecting Explore -> Display Summary from the context menu.

The display summary for the VISA-GPIB object vg is given below.

• VISA-GPIB Object Using NI Adaptor : VISA-GPIB0-1
  
  Communication Address 
     BoardIndex:         0
     PrimaryAddress:     1
     SecondaryAddress:   0
  
  Communication State 
     Status:             closed
     RecordStatus:       off
  
  Read/Write State  
     TransferStatus:     idle
     BytesAvailable:     0
     ValuesReceived:     0
     ValuesSent:         0
  

Using Vendor Tools to Identify and Test Your Resources

The VISA-GPIB Address