Speed up daq counter

Question

Hi,
I'm trying to determine the pulse width of a signal by using the counter of a NI USB 6216. This works reasonably well, except the acquisition is too slow for my needs.
Below you can see a stripped down version of my acquisition vi. In the version depicted stage 2 of the loop takes 3ms to execute. This is the time expected to count the appropriate number of low times (20) in the signal I'm measuring. The whole loop takes 30ms however (measured beginning to end of loop - not beginning to beginning of next iteration).
If I remove start task and stop task vis the loop time doesn't change, the whole time apparently taken up by the read vi.
I'd like the loop to run with less overhead (ideally none :-). Can anyone with more experience shed some light on how to speed up this vi?
Regards Florian
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Answer 1

Partially puzzled by two things that seem in conflict:
1. you're doing a finite triggered task that intentionally misses some pulses while it stops and restarts
2. you're expressing some concern about those missing pulses
One idea to make the stop and restart faster is to use DAQmx Control Task to "commit" the task before starting.
When you do that, cycles of stop and restart can occur much faster than they would otherwise.  An example and
some benchmark results can be found here.
Another idea is to perform continuous acquisition of the pulse measurements so you won't miss any.  Depending
on your app, that may leave you with the job of timestamping the trigger signals with another counter, and
working a scheme to correlate particular pulse measurement subsets with particular trigger events.  Not a trivial
job, but a do-able one.
-Kevin P
P.S.  Just re-checked and noticed you're using a USB board.  I suspect that's a significant part of the problem.
There's more latency & overhead with USB acquisition, and the effect is stronger when you request small packets
at a high rate than if you requested large packets at a lower rate.
P.P.S.  Looks like you alread got an answer before I hit send -- I was just typing a minute here, a minute there
while do some other testing.