create 4 digital output pulses base on input ttl signal

[noli]

Hi

    I am a beginner in Labview and would appreciate any advice on how to solve the following problem.

I am creating a TTL pulse train, and would like to send that into Labview as input.  For every falling edge detected on the input signal, I'd like Labview to generate 4 digital output pulses.  For each output pulse, I'd like to be able to specify the delay, and duration.       The picture should illustrate it more clearly, with the numbers showing the intended order of magnitude.

 

System:  NI PCI-6733 DAQ card, Labview 8.5

My daq card has 2 24-bit timers, and 8 digital I/O but I don't know what the best approach is for creating between 4-8 output pulses of this precision..should it be handled in hardware, or in software?  And how would I go about it

Thanks,

-Sidney

[YannC]

Hi noli,
I made a little example, have a look to this example.

You need to connect the Digital Input in PFI0. I hope this example will help you.

If you have any question you're welcome.

 Regards

Message Edité par YannC le 02-20-2009 08:40 AM

[noli]

 Hi Yann,

   Wow, thank you so much for this example!  I'm trying to take a look at it, but when I run it.. it responds with the following error message

Error -200452 occurred at Property Node DAQmx Trigger (arg 1) in DAQmx Start Trigger (Digital Edge).vi:1->reprise-1.vi

Possible reason(s):
Measurements: Specified property is not supported by the device or is not applicable to the task.

Property: Start.TrigType
Task Name: _unnamedTask<49>

This is strange too, because ive already used the Digital Edge Start trigger for a different application with this card.

-Sidney

[YannC]

Hi,

Can you test without the trigger vi, I don't have a PCI 6733 to make the test.

Regards

[noli]

So I'm not sure I understood you correctly by "test without the trigger vi", but I deleted the DAQmx trigger vi from the back panel, and reconnected all the wires.  When I put in sample vaules for the pulses, and run the program, it doesn't produce any errors..  yet doesn't produce any pulses either...  which, I suppose is normal because the pulses should only be produced when it receives a trigger.  Was this what you meant by testing without the trigger vi?

-Sidney

[YannC · Accepted solution]

Hi noli,

I found where is the problem, in fact the PCI 6733 only support software Digital Output timing. The software timing is limited to 1 kHz in better case.

I'm sorry but this function is not feasible with a PCI 6733.

Regards

[noli]

Hi Yann,

   I see the problem now.. from what I read it looks like all DAQ cards using DAQmx have this problem where they must use software timing as well.  Ok, Thanks for all of your help!    There's someone in our group who created an analog version that alos does what we need, but i'll repost that code under a different thread.

-Sidney