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trigger digital output task

My problem is rather complicated, however I think I can condense it down into a simple question: Can you trigger a DAQmx Digital Output Task (Digital 1D Bool N Chan 1 Samp)?

 

Whenever I try, it gives me the error: "Error -200452 occurred at Property Node DAQmx Trigger (arg 1) in DAQmx Start Trigger (Digital Edge).vi2 -> Untitled 1"

The possible reason it gives me is "Specified property is not supported by the device or is not applicable to the task"

 

I'm hoping I just haven't configured the task correctly, but I fear that the fact is simply that you cannot trigger a single sample digital output... I can trigger a single sample analog output, so why not digital?

 

The full extent of my problem is this:

I'm using a voltage controlled current source to send a bi-phasic square current pulse to a grid. Where on the grid the pulse goes to is determined by 2 addresses sent to 2 demultiplexers. The addresses come from the digital outputs of my PXI, and the voltage that controlls the current comes from an analog output.

 

The issue I am having is that I need the current to be bi-phasic (positive, then negative), but my current source can only supply positive currents. I have determined to overcome this by simply swapping the addresses in the middle of the pulse, i.e. the current flows from address 1 to address 2, then halfway through the pulse I swap the addresses and it flows from address 2 to address 1. 

 

I need to control the timing of all of this, so I decided that the best way to do this would be to generate a pulse with one of the counters, trigger the analog signal on the rising edge, and the address swap on the falling edge.

 

So I need to be able to trigger the task to write the address, which is a 1D boolean array of 4 elements being sent to digital output lines.

 

If there isn't any way to trigger the multi-channel single-sample digital output, can you suggest some other method to control the timing between the execution of two different DAQmx tasks?

 

My card is a PXI 6115.

 

Cheers,

Josh

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Hello Josh,

 

Here's a document that describes the specific error you're seeing:

http://digital.ni.com/public.nsf/allkb/05A563FE3AA7B3C286256FF90077C303?OpenDocument

 

Could you post a screenshot of your code, or at least just the part where you configure your task?  It might help us to see how you've configured it.

Michael B.
Applications Engineer
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