Paolo Mantegazza wrote:
>
> Hi,
>
> > I want to generate squares from parallel in the highest frequency and
> > stable needed. pthread_create() and pthread_make_periodic_np() only give me
> > the stable square wave about 30k HZ. I need 120k HZ or more.
>
> Forget about that. On whatever PC, with whatever real time OS, you'll
> have jitters greater than the period you want.
He is using it for a stepper motor where jitter is less important than
pulse speed.
> 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?
> 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).
- Cheers, Kal.
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