It'll help to know what board you have and more details about the app.
The simp-lest approach is software-timed. Stop the task (but don't Clear it) to turn PWM off. Start it again to turn it back on. This method allows you to vary the timing between on and off cycles. However, you won't be able to get absolutely reliable 1 msec intervals without a real-time OS.
Another approach is to configure your PWM generator to be "pause-triggered" by another counter. Your PWM generator will then produce output only when the other counter's output is, say, high. This method allows you to produce precise and repeating on-off cycles.
-Kevin P.
ALERT! LabVIEW's subscription-only policy came to an end (finally!). Unfortunately, pricing favors the captured and committed over new adopters -- so tread carefully.
Thanks for the expanation and tips. I'd like to elaborate a little bit to help TEster out:
A software-timed task (one that turns the pulses on and off using commands in the program) will be very slow, event with the LabVIEW Real-Time OS. The Windows OS has a jitter of about 10 ms. This means that if you want to turn a pulse on, then off every 1 ms, it could take up to 11 ms to perform. LVRT is deterministic, so it executes a timed loop in exactly the same amount of time, every time. But it isn't necessarily faster than Windows.
As you said, a DAQ or counter/timer device has onboard counters that can be paired to generate a hardware-timed PWM signal. This is a MUCH faster output with deterministic timing, since it's driven entirely in hardware. A simple modification to a DAQmx shipping example yields the result (attached).
David Staab, CLA Staff Systems Engineer National Instruments
