Count Squares with 500Hz

[XS-er]

Hi!
 
I've generated with the ExpressVI "Simulate Signal" a Square with the maximum frequency of 500Hz (it varies). Now I want to count the falling flanks.
I tried this with the "Trigger Counter.vi"-Example which I slightly changed for my purposes. (see attached file) But it seems as if the Counter is not fast enough for my Signal (- it counts too slow).
 
Does anybody have an idea how I can solve the problem and count the correct value of squares?
 
Shorty to my system: I tried it with a 2GHz Sempron with LabView8 
                                      and with a 1,3GHz Centrino with LabView7.1
 
Thank you in advance
  Hendrik

[AnalogKid2DigitalMan]

Puplicate Dost, see here:

http://forums.ni.com/ni/board/message?board.id=40&message.id=3422

[XS-er]

I know! I already asked the Admin to delete the post in the HardwareBoard.

I accidently posted it there first because it maches to the topic "Counter/Timer". But I'm looking for a software solution. So I posted it again in this board!

Sorry for unintentional spamming... 😞

I hope nevertheless that anybody has a solution for me...

[AnalogKid2DigitalMan]

Hendrick

No problem, welcome to the forums .

It's common to flag duplicate posts to prevent duplicate efforts at solving a problem. Thanks for asking the Admins to delete one.

I am sure some will be able to assit.

[falkpl]

If you have a simulated square wave waveform, you can count falling edges by simple emulating what a counter does, essentially for each poind threshold it.  If it is above some threshold it is a high value, and if it is below th it is low, use a shift register to compare sequential hi/low booleans.  Check for a high to low transition (if n-1 is high and n is low there is a falling edge) use another shift reg to count these events.  Do this for every point in the waveform.  If you have simulated a noisy signal, you can get more advanced usint techniques such as a schmitt trigger (hysterisis).

Paul

[XS-er]

Thank you very much Paul, your solution is working fine and it is so easy that I'm a little bit ashamed that I posted that question!

[falkpl]

No problem, the answer always seems much easier once you have seen it.

Paul

[shuishen1983]

Do you have the trigger counter.vi? I don't have it in my examples.