re:Dougs step/dir plan was Re: Bullet-Proof G201 / G210

Chris,

Doug is correct. Given 2 axes: Except for 45 degree moves, there are
two different pulse rates required, which means that most of the
time, the step pulses(and their attendant dir bits) are not happening
at the same time.

Doug is also trying to capitalise on the microsecond capability of
current pc CNC software, combined with the mechanical latency of
motors. So instead of sending out all moving axis dirbits with all
movingaxis stepbits, with the dirbits set as needed... We send out
+dir on all axes needing it as one operation, and VERY slightly later
send out the steps on axes moving the other way (after changing the
shared dir line)

The microsecond nature of this "two outs per step- one for the +dir
moving axes, one for the -dir" would, In Dougs explanation, be do-
able without causing problems for linear or circular interpolation.

I don't necessarily like this approach, but it does seem do-able
(except for Geckos), and hope that this explanation makes what he has
proposed clearer,

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Chris L <datac@l...> wrote:
>
>
> Doug Fortune wrote:
>
> >Everything we normally do, lathes, mills, routers, and
> >also hexapods (Stewart Platforms). Saving output pins
> >means more functionality in your machine, because those
> >output signals can now be used for something else.
> >
> Clearly this is a good reason for "Black Box" control techniques.
Using
> a "proprietary" language (which of course could be shared if the
> developer desired to), communicating with external hardware via USB
or
> even serial port can eliminate some of that. I have heard rumors
>
> >>It would appear to be for some type of "single axis at a time
positioning"
> >>
> >>
> >
> >Absolutely not!
> >
> >This is a general scheme. In fact, moving axes together at
exactly
> >the same time (other than for 45 degree moves) is statistically
> >exceptionally rare ...
> >
> Maybe by a "hand cranker".... but, On a CNC mill or Router ?? Now
I am
> lost..... Even on my simple 3 axis router, I assure you I can and
do
> have more than one motor turning, and in opposite directions at any
> given time, even for simple 2d profiles. How could one cut a 2d arc
> where I would need to have negative movement in X and positive
movement
> in Y, yet having only one direction available ?? I hate to even get
into
> full 3d continuous motion work where if I do not have the option to
run
> motors at any direction at anytime.......
>
> Not sure I'd want to give up the ability for turning any motor any
> direction I want, at any time.......
>
> I probably missed something. My better half says I never listen
very well !
>
> My eyes don't read so good either anymore, not to mention the brain
that
> is slowing down !
>
> >but it won't work
> >for the current generation of G201/G210/G320/G340 because
apparently
> >the direction pins can't be changed arbitrarily after a step pulse.
> >
> Now this I am a little familiar with as Flashcut had a hard time
driving
> them. To my knowledge, Marriss and Flashcut have discussed it
> thoroughly. As far as I know, FC can run them now. I know FC has
added a
> few extra driver adjustments in order to get a good "grip" on every
> driver one might end up using.
>
> Not being confrontational, Just was trying to get an idea where you
> wanted to use that concept. I'm sure there is a use for everything.
> thanks,
> Chris L