Pretrigger samples with keyboard trigger?

[hter]

Hi,

I am very new to Labview, so this may not be a difficult problem but I can't find the solution. I have built a vi to record sound using the NI USB-6251, but I would like to obtain a certain number of samples prior to a trigger. I see in the DAQmx Reference Trigger VI that there is an option for pretrigger samples, but the only way to trigger this VI is via a signal into one of the channels. This does not work for us because we wish to record all 8 channels at the maximum sampling rate. I was wondering if there is an option for some kind of manual trigger (such as a key or mouse click) to obtain pretrigger samples?

Thanks,
Hannah

[DanBrowne]

Hi,

This is the general method I would suggest:

You could use an Event Structure to read a mouse click or keyboard button press, which in turn, when the event is triggered, would then set a digital output (for example) on your 6251 high, which would be wired into the trigger input for the 6251. This would then start the triggered acquisition. If you have any other questions regarding this I'll be happy to answer them.

Regards,

Dan - NIUK