Count Digital Edges Using the USB-6008/9 in LabVIEW

Updated Jan 11, 2018

Reported In

Hardware

  • USB-6008
  • USB-6009

Issue Details

I have a USB-6008 or USB-6009 and I want to be able to count digital edges or events in LabVIEW. I have tried using the Counter Input example programs in LabVIEW but no matter how I configure the channel settings I get error -200077 saying the "requested value is not a supported value for this property."

Solution

You can configure PFI 0 as a source for counting digital edges. In this mode, falling edge events are counted. DAQmx Create Channel function has a terminal for edges that defaults to rising if unwired. When using the USB-6008/9 you must create a constant or control that sets the channel to count falling edges. 

Additional Information

In the LabVIEW Counter - Count Edges.vi example program, the active edge being counted is changed using a property node. Even if you set the value of this property to be falling, LabVIEW still gives an error when using the USB-6008/9. This is because the DAQmx Create Channel function is called first and it defaults to the rising edge when nothing is wired. To solve this issue you must also wire a constant or control into the edge terminal of the function and set it to falling. 

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