How can I syncronize the analog input?

[otlm]

The signal coming from the microphone input of the DSP module, displayed on Waveform Graph, is "slipping".

How can I syncronize the analog input?

Thank you!

[DFGray]

Synchronization can be done in hardware (usually) and software.  However, you have not given us enough information to help you.  Please tell us what hardware you are using and how you are using it (wiring, software, drivers, etc.).  Also tell us what you mean by "synchronization." Then we can help you properly.

LabVIEW has a variety of ways to trigger waveforms, if that is all you need.  Search for "trigger" in the palettes.

[otlm]

Hi DFGray!

I have uploaded a video, hopefully it showes my problem.

Here it is: http://www.youtube.com/watch?v=DVgv3WH3Y2U

I use Speedy 33 module, external signal generator, and microphone.

I would like to have a "standing" picture.

I do not know how I should adjust the 'trigger', I do not find it.

Thank you very much for the help!

[DFGray]

I have never used the Speedy 33 module, so cannot comment on its capabilites, but would not be surprised if there is no trigger on the microphone input.  Most hardware does not have one there.  However, you can use the Trigger and Gate Express VI to do what you want to do in software.  See the LabVIEW help for details.  Let us know if you run into problems.

[otlm]

The "Trigger and Gate" I can not use.
Block diagram error: SubVI is not exetutable!
The trigger problem exists on both inputs.
Is there another solution?

[DFGray]

That's odd.  What version of LabVIEW are you using?  And do you have the base, full, professional, or student version of it?  It sounds like you are either missing something or not generating the code for the Express VI correctly.  If you have the base version of LabVIEW, this could be why.  Did you get a configuration dialog when you dropped the Express VI?  In any case, please post your code so we can have a look.

Basic Level Trigger Detection will also allow you to find a particular start point of a waveform.  However, if you want a particular length of signal or pretrigger data, you will need to buffer it yourself (the Trigger and Gate Express VI does this for you).  If you go this route and need to know how to buffer things, let us know.

[otlm]

In DSP project such opportunities are not!
If this is not a simple solution, it's a big problem.
Without any timing will not work.

[DFGray]

Ahh!  You are doing this on the DSP itself.  That would explain the Express VI problem, since you probably do not have floating point available.  A simple level trigger is not hard to code using integer math.  You can use the VIs I mentioned above as a guide (the algorithms should work well with integers as well as floating point) or just do it yourself.  A possible algorithm for a positive going edge trigger is the following:

1. Search array until first point is less than level and second is greater than or equal to level (use In Range and Coerce to search).
2. Extract array subset from your data starting at the point you just found.
3. If you need a particular length of data and are continously acquiring, append data from the next scan onto your data until required length is met.

If you run into issues, let us know.  Remember that shift registers are your friend.