Re: [CAD_CAM_EDM_DRO] Re: Shared Direction pins vs dedicated Direction pins

I'm amazed that there aren't solutions readily available that use Ethernet
connections rather than the parallel port.

Regards,
Tony

At 14:52 12/02/2003 +0000, you wrote:

>Bernard,
>
>Ditto.
>
>And even though the p-port is disappearing,(but will not "really" be
>gone for awhile) the current crop of pc-based cnc controllers is
>including support for additional i/o with the use of another p-port,
>or support of generic i/o cards, or usb, game port or otherwise...
>
>In other words, it's a solution in search of a problem, IMO.
>
>Ballendo
>
>P.S. But a neat idea!
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bernard R
><bwjarandall@c...>" <bwjarandall@c...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Doug Fortune <pentam@c...>
> > wrote:
> >
> > Doug,
> >
> > While there is no technical difficulty doing time division
>multiplex
> > with muliple controllers, I don't really see the need. The current
> > limitaion is using a single parallel port as the computer
>interface.
> > From what little I've seen the G2002 project is well in hand so the
> > limited output pins should soon be history.
> >
> > From the practical side I could see a lot of people having problems
> > with the concept and trouble shooting such a system would be a
> > nightmare for the average hobbyist with limited technical knowledge
> > and virtually no test equipment.
> >
> > Bernard
> >
> > > re: dedicated Direction & Step pins need 2*N output lines
> > > vs shared Direction & dedicated Step pins need N+1 output lines
> > > (N is number of axes), thus saving output pins which are limited
> > > in number on a parallel port, and hence often a constraint.
> > >
> > > Chris L wrote:
> > >
> > > > >>It would appear to be for some type of "single axis at a time
> > positioning"
> > >
> > > Doug wrote:
> > > > >Absolutely not!
> > > > >This is a general scheme for lathes, mills, routers and
>hexapods
> > >
> > > > 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.
> > >
> > >
> > > Hi Chris:
> > >
> > > Yup, lots of motors turning simultaneously at different speeds,
> > > accelerations and directions, thats how S&D motor drivers work
> > > (as you well know!).
> > >
> > > Yes, I think you are missing something obvious.... the Step
> > > signals to the motor drivers are of the order of 1 uS (1
>millionth
> > > of a second). Apparent smooth motor motion results from emitting
> > > one of these pulses (say 20,000 times/sec or once every 50
> > millionths).
> > >
> > > In other words, you could have many (50 channels in this example)
> > > sharing a common direction pin, and neither the motors nor the
> > human
> > > would be able to detect any measurable difference. However the
> > Geckos
> > > (much as I like them) have a hold-time constraint on the
>Direction
> > line
> > > which precludes their use in a "shared-direction" scheme.
> > >
> > > <more written offline to Chris>....
> > >
> > > Doug Fortune
> > > http://www.cncKITS.com
>
>
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Regards,
Tony