Re: Gecko drives and EMC

[Paul <paul-at-bdiemc.fslife.co.uk>]

Hi Robin

A 20KHz pulse rate equates to a PERIOD of 25uS (we need two interrupts for 
each step). As an example, I have an 800MHz Duron running at 16uS, and an 
Athlon 18000 down to ~8uS. I would have though a 1.2GHz box would be more 
than capable of generating a 20KHz signal.
There is one problem with running PERIOD at such small values - Interrupt 
latency. Depending on the motherboard chipset and DMA activity, this *could* 
be as high as 30uS. On a lightly loaded Athlon, I see around 10-14uS jitter 
when running PERIOD under 10uS. Increasing this parameter to 20-30uS, and the 
jitter dissappears.

Regards, Paul.


On Friday 28 Feb 2003 1:00 pm, Robin Szemeti wrote:
> I'm still trying to drive some Gecko drives and stepper motors to a decent
> performance with EMC.  The Gecko's are the 'microstepping' flavour (for a
> variety of reasons I need the fine control/smoothness of microstepping) ...
> the motors are produce good torque up to around 2Khz ... thus I need a
> 20Khz step pulse train into the drivers to reallise this potential.
>
> We've had this discussion before and it was consdiered even with a fast
> (1.2ghz+) cpu, 20khz would be pushing it.  That still the perceived wisdom?

-- 

"To err is human...to really f*** things up requires the root password."
>From a collection of quotes at http://www.indigo.org/quotes.html