Re: EMC with intelligent stepper controllers

[eric <eek105-at-psu.edu>]

John Guenther wrote:
> 
>   If I wanted EMC to work with an
> intelligent stepper controller, where would that type of driver
> need to be implemented in EMC?  

the external interface is defined in extintf.h.  You must write driver
that matches
with that interface somehow.

>Does that require a replacement for
> steppermod.o or freqmod.o or is there some place else that would need to
> be changed?

EMC wants to output velocity commands and get back position feedback.
I think the file you may want to start with is extsmdromot.c
If your hardware can't deliver that at a reasonable rate, then you may 
have to tap in to emc at a higher level than at the driver level.
There is a motion controller in emc in the file emcmot.c.  You may
have to substitute for that.  Motion coordination is the trick that you
have to accomplish somehow.

The thing that wasn't clear to me is why you would want to buy the 
board you mentioned when you could get emc to work with something
from Dan Mauch, for example, and you wouldn't have to hack into 
emc nearly as much.  From where i sit you are taking somewhat of 
a risk in starting this approach, unless the vendor has defined a method
of multiple axis coordination.
eric