High frequency digital pulse train output - timing problem

[AdamLeicester]

Hi,

I'm using an M series PCI-6251 multifunction DAQ card which I want to use to control a 2-axis traverse driven by 2 stepper motors with encoder feedback for position.

I already have one analogue output used up for another function (the card is used for another system in our wind tunnel as well) so can't use the 2 analogue outputs for stepper motor control (which from a bit of reading sounds like it might have been easier than using digital). I also need the two counters to read in the encoder inputs so can't use those to generate a digital pulse train for the stepper motors either.

I've been experimenting with software timed loops to generate a pulse train from a digital I/O line but can only reach 1kHz which doesn't drive the stepper fast enough. I looked into using the analogue input sample clock as a timing source but have had no luck getting this to work either.

In the end I aim to be able to vary a pulse train from 0-100kHz to achieve the full speed range of our stepper motor. Is this likely to be possible with the hardware restrictions I have or am I going to need to buy additional hardware to be able to achieve this?

Thanks in advance for any help!

[Kevin_Price]

I'd say get the hardware.  If you need variable speed and independent control of the axes, you're *really* gonna want to do this with counter pulse trains.  You can change speed on the fly without stopping the task, and the speed control for the two pulsetrains are inherently independent.  Anything you try to do with timed DIO is gonna get problematic for anything but fully pre-defined motions.

I'd recommend an X-series board if you can get it, because it offers a lot more bang for a little more buck. A 660x timer/counter board or another M-series board would also be options. 

-Kevin P