NI-DAQmx digital output question

[amccormi]

Hi,

I'm trying to setup  a DAQ card to run a MRI experiment. I have previously used Labview (pre-8.0) but not 8.0 so I'm not very familiar with the new stuff (I keep wanting to tab to change cursors). Basically my question is how do I send out a precisely timed digital pulse?

I consulted the help/example files, and all of them dealing with pulse generation talked about using counters. However, when I tried to run these examples, it said my card had no proper physical counter channels. The card is a brand new NI 6008/6009 USB DAQ card, but MAX and other utilities seem to say the card has no counter channels.

Digital I/O and analog input seem to work fine, but I can't figure out how to use the digital I/0 to get a fast pulse (~1 msec). It seems just calling "ditigal line 0 -- high", "wait 1 msec", "digital line 0 -- low" is not good enough, as that produces a pulse of ~4 msec in length, I'm guessing due to read/write time to the DAQ card.

So ultimately my question is this:

1) Am I missing some easy way to use what Labview calls "counters" on the DAQ card?

2) If I cannot use counters, is there a way to say buffer the pulse I want into a digital line so as to avoid the read/write time problem? For the life of me I cannot figure it out.

Thanks in advance,

Andy

[Dennis_Knutson]

The 6008 and 6009 are very low cost DAQ modules and they only have simple event counters and the digital I/O is software timed. There is no way to get a digital output more precise. Upgrading to a card with a counter/timer output or with hardware timed digital I/O is probably your only solution.

[Otis]

Hi amccormi,

Dennis is exactly right.  The USB-6008/6009 are low-cost DAQ products, and they do not contain counter output functionality.  You will need to purchase a DAQ device that has counter support and/or correlated digital I/O.

Here are just a few devices that might work for you:
NI USB-6251
NI PCI-6221


Regards,