Generate a pulse train, NI 9402 modules in cDAQ-9174 chassis

[IndianaJones]

I have two NI 9402 modules in a cDAQ-9174 chassis. 

When I output a pulse train on a specific PFI line of a specific module, the pulse train is output on the correct PFI line, but on BOTH modules. 

I want the pulse train to come out of only one of the modules.

i.e. I select cDAQ2Mod1/ctr1 to ouput a pulse train on PFI3 of module one.  I get the pulse train on PFI3 of module one, but I also get it on PFI3 of module two.

I am also performing a two edge separation measurement with a different counter, but I don't seem to have this problem.  (The measurement only works when I have the signals connected to the module I specified.)

-Paul

[Efrain_G]

That is definitley an odd behavior. How are you reading your PFI lines? Are you choosing a single PFI line to be exported in LabVIEW?

[IndianaJones]

I'm using the DAQmx "continuous pulse train" vi from the example finder. 

One of the controls parameters asks for a counter, so I choose one coresponding to a paritcular line on a particular module. It outputs the pulse train, but on both modules.

[Efrain_G]

Do you mean the Gen Dig Pulse Train-Continuous Dig Start.vi? How did you realize this happened? Do you have a separate LabVIEW program that uses those PFI lines? It could be that your unused PFI lines are not set at any particular level so it may look as if they were been triggered. Are you actually using both lines? We could try swapping the modules in your chassis.

[IndianaJones]

Yes, that's the one.  As I'm outputting the pulse train, I'm simultaneously trying to perform a two-edge separation on two external signals.  The way the counters are connected to the PFI lines, I have to have PFI 3 on Mod1 outputting the pulse train, and PFI0 and PFI3 on  Mod2 performing the two edge separtation.  To check the accuracy of my two-edge separation measurement, I have both lines on the oscilloscope.  I can see the pulse train output on PFI3 of Mod2, even though I specified it to be on Mod1. 

When I get back to the lab I'll post a screen shot of my block diagram.  It's not quite the same as Gen Dig Pulse Train-Continuous Dig Start.vi;  I've looped it with an instance variable so I may adjust the frequency on the fly.

[IndianaJones · Accepted solution]

Here's the Vi I'm working with.

Hmmm...  Looks like it's actually only after I've output a signal on that line.  Perhaps I should try clearing the line.

-Paul

[IndianaJones]

Turns out it was a problem with "Lazy Uncommit", where the PFI lines remain connected. 

Called "DAQmx Reset Device.vi" to disonnect the PFI lines from the counters, and Voila! problem solved! Kudos to all!!!