On Tuesday 28 April 2020 21:29:39 John Dammeyer wrote: > > From: Chris Albertson [mailto:[email protected]] > > Sent: April-28-20 6:13 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] A simple LinuxCNC system > > > > > *For a stepping motor driver with 10uStep per step that's still > > > pretty well faster than it can actually turn. * > > > > No, you missed the point. With 10 uS per cycle, the motor can step > > in steps that are a multiple of 10uS long. So it can be 6000 uS or > > 6010 uS but never 6011 uS per step. It is the step-size resolution. > > The pulse can be raised or lowered on each cycle. I think the max > > step rates would then be 20 uS or 50KHz which is faster than it can > > go. > > Hi Chris, > I think I didn't explain that well enough. A Gecko a 10 step per step > drive. What is commonly called micro-steps. Perhaps I should have > written it that way. > > 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. > > > BTW this only works because you have a very fast processor. If I'm > > running a stepper motor using my $1 (yes literally $1) > > microcontroller chip I can tell the hardware step generator the step > > period in units of 0.001 uS. one nanosecond I get 10,000 times > > better resolution. I think the FPGA based solutions do the same. > > That said, I doubt the nanosecond level resolution of the step > > period is really needed. > > Will you share some code on how you accelerate from 0 to 15kHz > stepping rate on your $1 processor? > > Thanks > John > If using the parport in EPP mode, you can set a reset time separately, so you can step at the base thread rate. As far as motor speed is concerned, the speed limit is generally the speed limit of the opto stuff in the driver, and I've run steppeers laying on the table at slightly better than 300 kilohertz with a 2M542 driver, or about 3000 rpm. zero torque at that speed of course. :) > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users
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