>
> At 11:58 PM 3/03/97 -0800, you wrote:
> >That is somewhat similar to what I did more than a decade ago.  I used a
> >couple of one-shots that were re-triggered by the encoder edges.  Along with
> >a flip flop or two it prevented the false triggering as the encoder vibrated
> >back and forth around one edge.  As I recall the time period of the oneshot
> >was set to less than the maximum encoder rate.  The idea came out of EDN (I
> >think).  This was in late 1983.  I really do wish I still had that circuit.

If you have two interrupt-on-change signals that can be enabled/disabled
seperately, it should be possible to design a jitter-resistant quadrature
decoder in software.  The key is to recognize the four states as 0x, 1x,
x0, and x1; any time one of the input changes and triggers an interrupt,
disable the interrupt on that input and enable it on the other one.  In
this way, you should be able to get excellent response while minimizing
overhead from contact jitter.  You will add one count worth of slop to the
current position report, but in many cases you'd want to add a count of
hysteresis anyway so it's a non-issue.