On 11/14/19 12:34 PM, R.Wieser wrote:
Dennis,
The R-Pi has never, to my knowledge, been billed as suitable
for industrial/real-time/process-control...
I have not read those specs to be honest. But for some reason I assumed
that a 1.4 GHz machine should easily be able to generate a 1.6 KHz signal,
even using Python. I was wrong. It can, but just barily and not without
jitter and hickups. Lesson learned.
Regards,
Rudy Wieser
The machine itself would be fine. But between Python and Linux (probably the
bigger culprit), there are lots of things that aren't interested in your
deterministicity.
Just run it bare-metal; I'm sure that's straightforward on an rPi and has no
gotchas or complications that would lead to days/weeks of frustration.
On an actually practical note; ever since they started baking the quasi-realtime
stuff into the Linux kernel, you've been able to use the whole
sched_setscheduler(2) family of calls (from C) to set a process's real-time
priority. That might get things good enough to do the job, though how one gets
there from Python I couldn't tell you. Naïvely I'd say to just use ctypes to
wrap those calls, but that's some low-level stuff to be getting into from a very
high-level language. Might work?
--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
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