Determine the Serial Configuration of Port in MAX and LabVIEW

Updated Aug 10, 2023



  • RS-232
  • RS-422
  • RS-485


  • LabVIEW
  • Measurement & Automation Explorer (MAX)



Operating System

  • Windows

How can I tell what serial protocol (RS-232, RS-422, RS-485) my port is currently configured as?
How can I determine what wire mode (4-Wire, 2-Wire Auto, etc.) my serial port is configured to use?

You can find this information in Measurement and Automation Explorer (MAX) or in LabVIEW using the Wire Mode attribute.


Follow the instructions below to access the Wire Mode in the Attributes tab of the VISA Test Panel.

  1. Open NI MAX from the Start Menu. 
  2. Expand Devices and Interfaces and select the serial port of interest. For remote devices, expand Remote Systems >> <Your Device> >> Devices and Interfaces.
Note: If you are unable to see the serial port on your device, refer to Serial COM Ports Missing in MAX or LabVIEW.  
  1. Select Open VISA Test Panel.

  1. In the Test Panel, select the Configuration option and open the View Attributes tab. 
  2. In the left column, search for the attribute Wire Mode. The Current Value listed in the right column is the serial port’s current protocol and wire configuration. For more information about the different wire modes, refer to Transceiver Modes on NI RS-485 Serial Cards.


This option allows you to programmatically read the Wire Mode attribute from different or multiple ports. Follow the instructions below to access the Wire Mode using a VISA property node. 
  1.  Add a VISA property node on your block diagram. 
  2. Wire the VISA serial session of the port of interest to the reference input. Alternatively, you can right-click on the reference input, create a constant or control, and select the port of interest. 
  3. Select Property >> Serial Settings >> Wire Mode to configure the property.  
  4. Right-click on the Wire Mode output to create an indicator. Refer to Serial Settings: Wire Mode to see the possible output values. 

Additional Information

To change the protocol or transceiver wire mode of the serial port, refer to Setting the Transceiver Wire Mode of Ports on NI Serial Boards

Note: Check the user manual of the device you are using to determine what protocol and wiring modes are supported for the port. The property node may present more options than are applicable for your port.