generate square waveform digital output on 6259

[BRBASTS]

Hello,

I would like to generate 3 'simple' square digital output waveforms on NI 6259 board of 80Hz.

Because of the wiring of my testing tool piloted by 6259 board, I cannot use the counter output but I need to plug on 3 output lines.

I have re-used a vi already existing and done by a subcontractor but the waveform generated on my DUT has not the frequencies expected (though it seems correct on the generated graph). Indeed, there are some square waveforms, but not continuous. Some kind of 'salves' and the frequency 'chosen' does not correspond to frequency measured. If someone has an idea to help me, I have not a big experience on labview yet!

Thank you!

[Kevin_Price · Accepted solution]

You have 4 unique digital states that are meant to cycle.  Each cycle produces 1 full period of each of your square waves.  If you want the outputs to be at 80 Hz, you need to define the sample clock to run at 4*80 = 320 Hz.

The other thing you see on the scope is that there are short bursts of pulses with relative long times between the bursts.  The timing during the bursts are what the tasks control.  The time between bursts is caused by your use of the "Run Continuously" button.  Also that after starting them, you end vi execution almost immediately rather than waiting for them to run a while.  Ending vi execution initiates LabVIEW's auto-cleanup.  Those things account for the brief burst time and the long-ish time between bursts.

-Kevin P

[BRBASTS]

Thank you Kevin for your explanation, I understand much better thanks to them, now this is ok.