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fpga pxi_trig issue with multiple cards

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I'm trying to get multiple cards to monitor and drive the same pxi_trig line.  The goal is to have all cards monitor the same trigger line.  When one card is told to trigger, the other cards should detect it.  I found a similar problem discussed here, http://forums.ni.com/t5/PXI/pxi-trig-problem/m-p/1013201, but I'm trying to avoid having a master / slave relationship.  Again I want any card capable of driving the trigger.  While I see that the issue was solved with the "Set Output Enable" method, I'm not seeing the expected behavior.

 

Any help would be greatly appreciated.

 

 

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Accepted by topic author --thatguy

Hi Thatguy, 

It looks like what you're doing should work.  As long as you reference the same trigger, they will all use the same physical wire on the PXI backplane.

I haven't followed the logic all way though, but I assume what you're trying to do is determine if that card is trying to drive the line, then set that to "Set Output Enable". 

 

One thing to note would be when the line is not being driven, it is pulled high.  I'm not sure if that could be what you're seeing or not. 

What behavior are you seeing? 

 

Dave T.

National Instruments
FlexRIO & R-Series Product Support Engineer
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Your item of note was the gotcha that kept things from working.  When not driving the line, it's pulled high.  So I changed the code such that:

 

when I want to trigger I write a False

when I monitor I negate the value I read

 

and it works perfectly.

 

Thanks

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