Instrument Control Toolbox

The GPIB-VXI Interface

The GPIB-VXI interface is associated with a GPIB-VXI command module that you install in slot 0 of a VXI chassis. This interface, along with the other relevant hardware, is shown below.

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

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

Refer to Chapter 3, Controlling GPIB Instruments to learn about writing and reading text and binary data, using events and actions, using triggers, and so on. Refer to Register-Based Communication to learn about accessing VXI registers.

Note    The VISA-GPIB-VXI object does not support the spoll and trigger functions, or the BusManagementStatus, HandshakeStatus, InterruptAction, TriggerAction, TriggerLine, and TriggerType properties.

Creating a VISA-GPIB-VXI Object

You create a VISA-GPIB-VXI object with the visa function. As shown in the preceding figure, each object is associated with:

• A GPIB controller installed in your computer
• A VXI chassis
• A GPIB-VXI command module in slot 0 of the VXI chassis
• An instrument installed in the VXI chassis

visa requires the vendor name and the resource name as input arguments. The vendor name is either agilent or ni. The resource name consists of the VXI chassis index and the instrument logical address. You can find the VISA-GPIB-VXI 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 property values during object creation.

For example, to create a VISA-GPIB-VXI object associated with a VXI chassis with index 0, an Agilent E1406A Command Module in slot 0, and an Agilent E1441A Arbitrary Waveform Generator in slot 2 with logical address 80

vgv = visa('agilent','GPIB-VXI0::80::INSTR');

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

whos vgv
  Name      Size         Bytes  Class

  vgv       1x1            644  visa object

Grand total is 18 elements using 644 bytes

After you create the VISA-GPIB-VXI 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 4-8: VISA-GPIB-VXI Descriptive Properties 

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

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

get(vgv,{'Name','RsrcName','Type'})
ans = 
'VISA-GPIB-VXI0-80'    'GPIB-VXI0::80::INSTR'    'visa-gpib-vxi'

Note    The GPIB-VXI communication interface is a combination of the GPIB and VXI interfaces. Therefore, you can also use a VISA-GPIB object to communicate with instruments installed in the VXI chassis, or to communicate with non-VXI instruments connected to the slot 0 controller.

The VISA-GPIB-VXI Object Display

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

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

VISA-GPIB-VXI Object Using AGILENT Adaptor : VISA-GPIB-VXI0-80

Communication Address 
   ChassisIndex:       0
   LogicalAddress:     80

Communication State 
   Status:             closed
   RecordStatus:       off

Read/Write State  
   TransferStatus:     idle
   BytesAvailable:     0
   ValuesReceived:     0
   ValuesSent:         0

Register-Based Communication

The VISA-GPIB-VXI Address