Loop time too long...?!

[Wouter]

I'm making an application which sends (digital)signals with a NI
USB6009 (usb I/O).
Now I want to send a pulse train with pulse widths of 1 ms. (so 1 ms
high, 1 ms low)
My problem is that the time needed in the loop(s) to produce the signal
takes more then this 1 ms (in fact about 5 - 12 ms). The signals are
constantly produced and cannot be fixed. Right now this is fixed to 1
ms just for the test/dev phase of the program. Lateron they will be
made via a random generator (1-700 ms).

I already tried to use timed loops (LV8) but that don't seems to solve
it... I Also tried to clean up all "unneccesary" code, so no extra
delay is created, but still the loops take too much time.

So I need a sollution which is fast enough to produce a pulse train
like I mentioned before. Anyone any experience and/or sollutions on
this? (so without any NI RT sollutions...)

thanks!

[shoneill]

I'm nor familiar with this I/O hardware, but can't you make an output pulse train controlled by hardware? i.e. well over 1kHz rate?

I do faintly recall being able to input a "pattern" into a buffer for high-speed digital I/O (Array of Booleans or U8 I think) which can then be updated at the required speed (well over 1kHz).

Check the advanced Digital I/O VIs for your hardware.  Please bear in mind that I haven't done any DAQ I/O for a while, and have no experience beyone LV 6.1.

In other words, if it turns out I'm talking rubbish, I kinda told you so........

Just checked the DIO VIs present in LV 6.1, and it seems quite possible.  See the attached pic of my help file.  It should be easy enough to gewt this to output a pulse train.....

Hope this helps anyway

Shane.

PS You also need to use DIO COnfig and DIO Start to set the ports and the speed of the updates.....

Message Edited by shoneill on 03-08-2006 03:24 PM

[Dennis_Knutson]

I think you're going to have to get a better DAQ board than the USB-6009. The digital I/O of this device is software timed and you will not be able to get reliable, repeatable pulses with software only.

[shoneill]

Oh well,

That seems to be that then.  As I said, I don't have XP with that I/O unit.

Sorry.

Shane.