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Get Started with 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 serialport object. Therefore, only functions and properties that are unique to VISA's serial port interface are discussed in this section.

Refer to Serial Port Overview for more information about serial port communication.

Create a VISA-Serial Object

Create a VISA-Serial object with the visadev function. Each object is associated with an instrument connected to a serial port on your computer.

visadev requires the resource name or alias as an input. The resource name consists of the name of the serial port connected to your instrument. You can find the VISA-Serial resource name or alias for a given instrument with the configuration tool provided by your vendor or with the visadevlist function. Define the alias using your VISA vendor configuration tool.

The VISA-Serial resource name has the format ASRL[port_number]::INSTR.

For example,use the VISA-Serial interface to connect to the COM1 port, use the following command.

visaserial = visadev("ASRL1::INSTR")
visaserial = 

  Serial with properties:

         ResourceName: "ASRL1::INSTR"
                Alias: "COM1"
                 Port: "ASRL1"
             BaudRate: 9600
    NumBytesAvailable: 0

  Show all properties, functions

The VISA-Serial object visaserial represents a connection to your instrument. Click properties in the object display to see a full list of VISA-Serial properties.

              ResourceName: "ASRL1::INSTR"
                     Alias: "COM1"
                      Port: "ASRL1"
                  BaudRate: 9600
         NumBytesAvailable: 0

                      Type: serial
             PreferredVisa: "National Instruments VISA"

                 ByteOrder: "little-endian"
                  DataBits: 8
                  StopBits: 1
                    Parity: none
               FlowControl: none
                   Timeout: 10
                Terminator: "LF"

     BytesAvailableFcnMode: "off"
    BytesAvailableFcnCount: 64
         BytesAvailableFcn: []
           NumBytesWritten: 0

          ErrorOccurredFcn: []
                  UserData: []

You can use dot notation to configure and display property values. For more information about configuring these properties, see visadev Properties.

You can communicate with your instrument using the visadev Object Functions.

Configure Communication Settings

Before you can write or read data, both the VISA-Serial object and the instrument must have identical communication settings. Configuring serial port communications involves specifying values for properties that control the baud rate and the Serial Data Format. These properties are as follows.

VISA-Serial Communication Properties

Property Name

Description

BaudRate

Specify the rate at which bits are transmitted.

DataBits

Specify the number of data bits to transmit.

Parity

Specify the type of parity checking.

StopBits

Specify the number of bits used to indicate the end of a byte.

Terminator

Specify the character used to terminate commands written to the instrument.

Refer to your instrument documentation for an explanation of its supported communication settings.

See Also

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