Is it possible to generate a 70kHz square wave with the DAQCard DIO-24 card? I can only get it at 2.7kHz. But with this, it's only a pulse wave, and not even a square wave.
That card can't do it. It is a static digital I/O which means it has software timing only. The best you can do with Windows and the timed loop in LabVIEW 7.1 with any kind of determinism is a 1msec loop time. You will need to use a different board. You could a counter timer output or an analog output of a D/A DAQ board.
NI has several PCMCIA cards like the DAQCard-6062E and 6036E. These are multifunction DAQ cards. I don't know if there's a card with only counter/timer or digital pattern I/O available in PCMCIA. Your best bet for getting the correct card is to contact your local NI Sales Engineer. You could also go to NI.com and check their products on-line.
