> -----Original Message-----
> From: Peter C. Wallace [mailto:p...@mesanet.com]
> >> double step on this page may do that
> >> <http://linuxcnc.org/docs/2.8/html/hal/parallel-port.html
> >> <http://linuxcnc.org/docs/2.8/html/hal/parallel-port.html>>
> >
> > Nope. From the doc. "What is the maximum step rate? Remember, two periods
> > to
> > make a step. You settled on 16uS for the period, so a step takes 32uS. That
> > works out to a not bad 31,250 steps per second."
> > The clue in that bit of text is the step len and step hold times are not
> > nanoseconds but BASE_PERIOD events. So my original thoughts are still
> > correct. The BASE_PERIOD is chosen to create the fastest possible step rate
> > within reason taking into account latency.
> >
> > Now the source code makes more sense. Was a bit confusing thinking the
> > steplen was nanoseconds.
> >
>
> The steplen _is_ specified in nanoseconds, and you can generate 1 step per
> base
> thread invocation by using the double step mode (reset mode)
>
> This is described in the hal_parport manual
>
>
I couldn't find that reset mode in the hal_parport. At least not how you could
have a step that lasted 5uS when the base period was 35uS. How's that timing
calculated?
OTOH, the code variable names are clearly referring to nanoseconds.
for (n = 0; n < num_chan; n++) {
/* decrement "timing constraint" timers */
if ( stepgen->timer1 > 0 ) {
if ( stepgen->timer1 > periodns ) {
stepgen->timer1 -= periodns;
} else {
stepgen->timer1 = 0;
}
}
>
> >
> >
> >
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>
> Peter Wallace
> Mesa Electronics
>
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