Parallel Port Limited frequency

[cyrik]

Hi!!

I have a question for you!

I need to control stepper motor driver with the parallel port. I'm able to do that with VISA or the Out.vi.

I need to go at 1kHz for example. But i'm juste able to go with VISA at 500 Hz and with out.vi at 200 Hz.

How I can go faster ???

You can see my code below. For the frequency, I put a timer . When i'm going faster then 200 Hz the frequency seem not to be what I hope! For example 340 Hz give to me 498 Hz, but at slowly frequency everything is ok.

Thanks For all

P.S. Sorry for my english!!

[Bobillier]

I don't know if you can run more faster, but you can try with the direct port access vi instead of Visa. You can find this vi in \vi.lib\Platform\portaccess.llb

About your Vi, I don't think your structure choise is good. You Have two while structures in parallel but they aren't synchronize. When you change the state of your output via the local, you are not sure

than the visa is ready to read it . In your case the time limiter is the speed of visa session. It's better if you change state, update the ouput, wait, Change your output state and replay this sequence in same while structure.

Have look at labview exempl (Parallel Port Read and Write Loop.vi).