Re: Re: VISUAL BASIC & CNC

Luis

There might be a third way and that is to pass the motion info over network
to a linux black box from your windows app. This was demoed at last year's
NAMES Expo. EMC is capable of developing a rather good pulse train and can
do it in a rather sparse environment. The only question I'd have is how far
ahead of axis motion can your Visual Basic program afford to be?

You could send g-code, or cannonical position commands, or cubic splines, or
even some sort of number of steps for each motor in the next motion loop.
You would just need to buffer these ahead a bit to allow for latency in the
pulse train from the MS-Windows machine.

Ray

>    From: "abbylynx" <abbylynx@...>
> Subject: Re: VISUAL BASIC & CNC
>
> Luis,
>
> Short answer: no
>
> Long answer: Controlling steppers requires a steady pulse source at a
> high frequency. Under Windows this is simply not possible (even with
> a realtime priority thread and a multiprocessor system). While you
> may be able to get it to move at slow speeds, with some degree of
> success, the moment you try and go faster Windows will snatch a  few
> milliseconds here, and a few there - your motor will be racing along
> with intertia and will fly through steps, and you'll lose your
> position. If you go REAL slow, you might be okay..
>
> My advice? Get yourself a midware device - something that hooks onto
> serial, or that gives you a card. This way your windows program just
> sends commands to the card/controller at its leisure and the
> controller works to deliver solid steps. There is a project out there
> that uses a "dumb" DOS PC to control a stepper setup - the controller
> PC (running windows) is connected to this via serial, and the dumb-
> box is connected to the stepper board via parallel.
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "luisguillermo98"
>
> <luisguillermo98@y...> wrote:
> > Hi group,
> > My projects includes a controller, sensor switches, valve and
> > steppers. I am wondering how to write program in visual basic
> > (using .DLL to controll paralel port in c language) to move the
> > stepper without loosing step. I heard that pulse are not sent
> > properly in a windows enviroment and that is why most CNC programs
> > are writen in DOS or linux to prevent this but I need to run my
> > applications in a windows enviroment so my question is how can the
> > pulse or signal can be send properly or rechecked  to the parallel
> > port so stepper motors can run smoothly without loosing steps?
> > 
> > luis..