On Tue, 28 Apr 2020, John Dammeyer wrote:
Date: Tue, 28 Apr 2020 19:09:00 -0700
From: John Dammeyer <jo...@autoartisans.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net> To: "'Enhanced Machine Controller
(EMC)'" <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] A simple
LinuxCNC system
As far as LinuxCNC goes, to me it appears the parallel port code given the
steplen calculations there isn't a way to bring the step
pulse low again during the same BASE_PERIOD interval which in the HAL file
example is 24uS not 10uS. Therefore I interpret the step pulses to be twice
the BASE_PERIOD time.
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."
But then it goes on to show that the real restriction in their example was the
dir hold setup time and by changing those parameters the step rate can be
increased.
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.
Thanks
John
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
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Mesa Electronics
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