Re: A crazy idea

Mariss,

This does indeed correspond closely to a magnetic
recording scheme called Manchester encoding. It
works quite well as long as the source of the
pulses can reliably generate the short pulse that
you equated to 2 uS or less to indicate CCW.

Cheers,
Steve

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:
> Stephen,
>
> Good morning! This idea is not fully baked yet; it only occured to
me
> about an hour ago. Here's how it would work:
>
> (1) Trip a 2uS one-shot on the 0 to 1 transition of the STEP/DIR
line.
> (2) Have the STEP/DIR line connected to the conventional DIR input.
> (3) Have the one-shot Q-not go to the conventional STEP input.
>
> The one-shot would fire on every STEP/DIR pulse leading edge. It
> would time out in 2 microseconds. The Q-not output would then trip
> the STEP input.
>
> If the STEP/DIR line is "0" at that time, the DIR would be CCW. If
> the STEP/DIR line is "1", then the DIR would be CW.
>
> In other words, if the STEP/DIR line is "1" for 2uS or less, the
> direction is CCW. If it is a "1" for more than 2uS, the direction
> would be CW.
>
> It is conventional for step pulses to be a constant width, say 1uS.
> It is also convetional to invert the pulse polarity. The polarity
> inversion would function as the "direction bit" then.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "stephen_stallings" <stevesng@n...>
> wrote:
> > Hi Mariss,
> >
> > This sounds a bit like the encoding schemes used
> > to record data on magnetic media. All that I am
> > aware of have a time sensitive element that
> > requires a one-shot or a PLL to recover the data.
> >
> > Can you describe how you would recover the data
> > in the case of one step CW, pause, one step CCW,
> > pause, one step CW?
> >
> > If time is a factor, then the software and the
> > motor driver would have to agree and conform
> > to a common time scale. This could be troublesome,
> > as we already have problems with pulse jitter at
> > high step rates.
> >
> > Regards,
> > Steve Stallings