Timed loop - Configure Clock "source name" - NI USB 6259 ? ? ? ? ?

[SurfaceSurfer]

Hello,

I've been trying to configure (i.e. specify) the timing source for a timed loop. I've tried numerous approaches from examples in the forums and with LV but can't get it to work.

When I get into "Configure Timed Loop" the 1MHz clock is greyed out.

Meanwhile when I use the DAQmX Timing.VI I have a plethopra of clocks to choose from (as it would seem) including:

- Onboard clock

- ai/sample clock

- ao/sample clock

- 20MHz timebase

- 80MHz timebase

and more.....ahhhhhh

Frustrated b/c I know this is something very simple!

Anyone want 5 stars

anyway using LV 8.0 and 6259 USB DAQ

thanks in advance

ss

[Gabi1]

you probably have a fast enough computer, so it is not your problem.

could it be that since it is a USB device, you cant use its onboard clock?

Message Edited by Gabi1 on 04-30-2007 04:33 PM

[SurfaceSurfer]

Yeah I'm not sure if the USB is limiting....

The specs say 1 channel @ ~2.8 Ms/s but I would imagine this can't be done unless one is able to assign a clock to it....

so far no luck in doing this so my update rate is too still too slow.

thanks

[Dennis_Knutson]

In order to get the max sample rate, you don't need a timed loop. You specify the internal clock of the device. It sounds like you might be doing on-demand or a single sample at a time. High sample rates are not possible in this mode. You might want to read the help on the timed loop and definitely check out the resources at http://zone.ni.com/devzone/cda/tut/p/id/5434 on DAQmx. For just starting out, try using the DAQ Assistant. You can even look at the code afterward to see what is generated. You should also look at the DAQmx shipping examples.

[SurfaceSurfer]

Yup, your right on the money....i.e. with respect to single sample at a time. Basically I'm doing a voltage ramp using the loop iteration as the multiplier.
So far looked at the tuttorials and maybe using part of a triangle waveform would work but probably easier just to generate my own linear waveform (looking into that right now).
thanks again for the help!

[Gabi1]

i think i understand your problem.

you wont be able to use the onboard clock for nothing else than input-output operations. timed loop are out of question.

if you want to time your output create the waveform in advance, then send the array directly to buffer using DAQmx.