Hi,
> He is using it for a stepper motor where jitter is less important than
> pulse speed.
That's wishfull thinking. You are loosing steps for sure, so you cannot
use the step motor without a position sensor.
> > So while you can use that
> > rate without jamming your machine the square wave seen on a memory scope
> > will be just a thick black strip.
>
> What do you mean by 'thick black strip'. Change the 'time/div' knob to
> a higher setting. Check your other scope settings. Use a scope with a
> rated frequency that is at least three times the desired sample rate
> (for analog scope). What scope are you using. At what settings?
I gave up the illusion of rates in that range long time ago. It is not a
matter of aliasing (3 times the sampling rate). You cannot obtain a
steady 120 Khz rate on PC motherboards, AS THEY ARE NOW.
> > Hands on experience.
>
> What code did you use for this experience? You need to wait at least 17
> uSec in RTL before doing your tests to account for Linux ISA bus
> accesses over the PCI bus to stop (a large source of jitter).
Simple toggling of a digital IO, either parallel port of DAQ card. Many
makers, ISA and PCI, under RTAI, RTL and VxWorks. I can tell you that I
got more stable results on older 286s under DOS, clearly for lower
rates.
Ciao, Paolo.
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