LabVIEW DAQ: Using a DAQ Trigger Occurence to execute a DAQ Continous Acquisition Occurence

[ChromaBurst]

This query relates to the following Zone examples from the Dev Lib:

http://zone.ni.com/devzone/explprog.nsf/webmain/B3C726699705BD288625679C000E0886?opendocument&node=DZ52309_US

http://zone.ni.com/devzone/explprog.nsf/webmain/D277E7EFD7C5DF5A862568660061CCF0?opendocument

This is my first foray into using DAQ occurences in earnest and has been brought around by the fact that once-again the AI Read loop in LabVIEW paralyses your CPU bandwidth for other tasks whilst waiting for a DAQ hardware trigger. I need to do instrument I/O whilst awaiting the DAQ trigger.

In my application I'm trying to provide the following a START trig, a GATE and a START/STOP pulse in ord
er to trigger the AI acquisition (user selectable). All data is streamed to disk in byte stream format and/or feed to a DS connection (CPU heavy!). I've played with providing a DAQ Occurence3 (trigger) mechanism so that I can pause for the trigger and not tie-up the CPU.

I really surprised that this so difficult, believe me I've tried all the documented (and undocumented) tricks to allow for concurrent operation of these two VI Server called parts of my application: 1) introduced wait states in the AI Loop 2) Changed the LV execution system for each section of my application i.e. DAQ exe system for the DAQ, Instrument I/O exe system for the instrument I/O etc.

Since the disk streaming is not the major factor here, does anyone have any ideas about how to to efficently wait for a hardware DAQ trigger using occurences and then use continuous AI acquisition also using occurences?

-ChromaBurst

[Filipe A.]

Hello;

There isn't a formal way to use Occurrences to wait and interrupt the CPU upon a digital event. What you can do to workaround that is to use the attached VI; that is an Analog Trigger VI, and set the analog trigger level to be the TTL levels. So, when the digital trigger arrives, your analog circuitry will trigger of the Analog input readings.

Hope this helps.
Filipe A.
Applications Engineer
National Instruments

[ChromaBurst]

Thanks Filipe, but you have completely missed the point. I already gave you this example! The question remains how is it possible to trigger a acquistion using the forementioned DAQOccurence3 example and THEN use another occurence for the buffered acquistion?? (the other example I sited)

-ChromaBurst