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DAQ Digital Output - Generate a pulse with specific width (in terms of time)

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How can I generate a digital pulse with a specific width? I haven't been able to find any examples online. Thank you!
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Message 1 of 11
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First of all, you have to have a DAQ with a timed digital output or a counter.  Then if you look in the Example Finder in LabVIEW (Help->Find Examples), you will find a few examples to do what you want.


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Message 2 of 11
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I've looked through the examples and I've found how to do it with a counter, but not with digital output.My DAQ has only 1 counter output, but I need to generate pulses on 2 separate lines. But I have a feeling I'm misunderstanding something.

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Message 3 of 11
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Hi,

 

 

Which DAQ device are you using?

 

 

Message 4 of 11
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USB-6000.

 

I'm following the example Counter - Continuous Output.vi from the Labview examples, and I want to use a property node to set the High and Low times, but this doesn't seem to be an availalbe option from the DAQmx property node when I have the USB-6000 plugged in.

 

The USB-6000 has a counter so why no counter properties are available?

If I can't change the property while the task is running, does this means if I want my program to be able to dynamically change the high and low times of my digital signal, I have to stop and start the task every time?

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Message 5 of 11
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Looks like I don't even have the option to set the CO.Pulse.Term option on this DAQ.

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Message 6 of 11
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The USB-6000 has only edge counting capability. It is not configured to generate pulses.  Look at the specifications (page 3) and the User Guide, Figure 3 and Table 4.

 

Lynn

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Message 7 of 11
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So what options are there for being able to generate a digital pulse of a specific width since all the examples I've found so far rely on a counter.

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Message 8 of 11
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Solution
Accepted by topic author achb

With the USB-6000 -- essentially none. It has only software timed digital I/O. Depending on your  system you may be able to generate pulses at rates up to a few hundred Hertz but there will be a considerable amount of timing jitter. Tens of milliseconds may be common and even longer variations may occur occasionally.

 

Please indicate what the timing requirements are for your pulses so someone may be able to provide a specific recommendation to meet your needs.

 

Lynn

Message 9 of 11
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Thanks. I'm not surewhat the timing requirements are, that's part of what I need to investigate.

 

I found this example for software timing:

https://decibel.ni.com/content/docs/DOC-6385

 

In the block diagram, they use a sequence structure to sequentially write high and low, and the Wait function to control timing. Does this mean DAQmx Write function with the Digital 1 Point 1 Line format, that the line will stay high/low until it is explicitly changed? Or, will it reset back to it's default high impedance state?

 

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