Re: [CAD_CAM_EDM_DRO] USC of Jon Elson

alex wrote:

>Understood.
>Bur should I in this case count pulses to know when to stop?
>
>

Well, the CPU can't see the individual pulses, and has no idea when they
are coming out. What it DOES have is a continuous reading of the
current position. But, you can't just turn it loose until the position
count is what you want, and then abruptly stop. The stepper motor
will skip steps, and end up moving a little further than you want.
You have to ramp the speed up to some reasonable rate, cruise
at that rate until you get within some range of the stopping point, and
then ramp the speed down, until you arrive at the stopping point and
with a velocity of zero. You can't do this with a simple loop in
software, it takes several loops, and probably a state machine type
of architecture. Having a real time clock to schedule the loops
gives more predictable control.

This all assumes you are talking about using my board. If not, you
really have to do all the same stuff, but you have to generate the train
of step pulses, too. You really need a real time system, or to be totally
sure that there are no OS routines that will steal time from your loops
to make your step pulses have timing jitter.

Jon