Receiving Only "\FF" Characters with VISA Read in LabVIEW

Updated Apr 25, 2018

Reported In

Software

  • LabVIEW

Driver

  • NI-VISA

Other

  • USB/RS-232 Adapter
  • Automation Direct PLC

Issue Details

I am sending a serial ASCII data stream over a USB/RS232 cable to my computer's COM port. I have tried using several example programs that utilize VISA Read but all I get out is \FF, over and over. I need some troubleshooting help or other suggestions.

Solution

Perform these steps to troubleshoot your system:
  • Verify baud rates and other configuration parameters based on your specific device. You should reference its manual.
  • Verify that the USB/RS232 cable is good. You can do a loopback test, or test it with another adapter cable.
  • Test the serial output of the device using another source. 
  • Open a VISA test panel to read serial data. This performs direct NI-VISA calls through your COM port. Refer to section 3 of this tutorial for more details.
  • Ensure that your device is set to output data in either ASCII or hexadecimal format
     

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