Can't Read or Write During Serial Loopback Test

Updated May 3, 2018

Reported In


  • LabVIEW 2014 SP1 Full


  • NI-Serial 15.0
  • NI-VISA 15.0

Operating System

  • Windows


Prolific Technology USB to Serial adapter

Issue Details

  • I am doing a serial loopback test on my target machine, but I can't read or write from the system
  • The device shows up fine in NI MAX but if I right click on it to open up a VISA test panel, nothing comes up. How can I pull up the test panel to troubleshoot?
  • When I do the loopback I get a VISA timeout error (for *IDN? command Write then Read and for a Query)


This can occur for a variety of potential reasons, but in one case, the following steps were taken to resolve the issue.
  • Reinstall your NI VISA driver from the web to include VISA Interactive Control and get the VISA test panel functionality
  • Refer to the troubleshooting steps found in the article Error -1073807298 Occurs after a VISA Read/Write to test for possible causes
  • Swap out the USB to Serial adapter for another one

Additional Information

You can also run NI I/O Trace while testing to see what VISA driver calls and errors occur, and it will also show you the processing time and other information about what is happening in your program. For more information, see Performing a Good NI I/O Trace Capture for Debugging/Troubleshooting


Not Helpful