Instrument Control Toolbox

The Serial Port Interface

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

• Creating a VISA-serial object
• Configuring communication settings

Refer to Controlling Serial Port Instruments, to learn about writing and reading text and binary data, using events and callbacks, using serial port control lines, and so on.

Note    The VISA-serial object does not support the serialbreak function, the BreakInterruptFcn property, and the PinStatusFcn property.

Creating a VISA-Serial Object

You create a VISA-serial object with the visa function. Each VISA-serial object is associated with an instrument connected to a serial port on your computer.

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 name of the serial port connected to your instrument. You can find the VISA-serial 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-serial object that is associated with the COM1 port, and that uses National Instruments VISA:

• vs = visa('ni','ASRL1::INSTR');
  

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

• whos vs
  Name      Size         Bytes  Class
  
    vs        1x1            640  visa object
  
  Grand total is 16 elements using 640 byte
  

After you create the VISA-serial 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 4-10: VISA-Serial Descriptive Properties 

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

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

• get(vs,{'Name','Port','RsrcName','Type'})
  ans = 
  'VISA-Serial-ASRL1'    'ASRL1'    'ASRL1::INSTR'    'visa-serial'
  

The VISA-Serial Object Display

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

The display summary for the VISA-serial object vs is given below.

• VISA-Serial Object Using NI Adaptor : VISA-Serial-ASRL1
  
  Communication Settings 
     Port:               ASRL1
     BaudRate:           9600
     Terminator:         'LF'
  
  Communication State 
     Status:             closed
     RecordStatus:       off
  
  Read/Write State  
     TransferStatus:     idle
     BytesAvailable:     0
     ValuesReceived:     0
     ValuesSent:         0
  

The VISA-GPIB-VXI Address

Configuring Communication Settings