using daqmx to acquire samples on digital edges continously

[diwi]

Dear all,

I want to take several samples of an analog signal on a digital edge (post-triggered), like shown here: http://zone.ni.com/cms/images/devzone/tut/a/25b19f241073.gif
I want to use a (NI-card) counter output (frequency around 30kHz) as digital signal.

But there are two problems:

1. I want to put it in a while loop, so that every 33 µs or so, the program waits for a digital edge again and takes samples again. So that the new values can be put in a different line of the array.

2. Ideally i want to wait for a digital edge, then wait for 20 µs, then take several samples, then wait for a new digital edge.

Howto?

Thanks in advance,

-diwi

[Broken_Arrow]

Do you want uS resolution on software running on Windows?

[diwi]

Well, the hardware can take samples at a rate of 1.25 MSPS, i can read the analog signal and take thousands of samples. I thought maybe this can be hardware timed? So i was wondering whether this was possible. Or do i HAVE to use Labview RT?

[diwi]

I know the while loop while take 1 ms at least, so i thought maybe i can put some daqmx blocks configuration in front to configure this automatically.

[andre.buurman@carya]

"normal" LabVIEW provides a millisecond timing resolution. E.g. the 1MHz timing source of the timed loop is available in LV FPGA, the FPGA supports this. But the real-time controllers FP, cRIO only support 1KHz source.

[reddog]

You didn't mention which hardware you're using, but I'll assume it's a multifunction DAQ board.  Doing this with hardware timing is accomplished by using counters in conjunction with your AI task.  See this thread for more information on how this is accomplished. You'll probably find several other posts on this topic if you search under the hardware boards. The only thing you won't be able to do with this approach is to have a fixed delay for when the acquisition starts from each trigger. You can have the board acquire N samples after each trigger (with about a 50 ns fixed delay from the trigger), but you won't be able to configure a programmable delay.