Just poll the encoders. A trackball doesn't spin very fast, and it's
non-critical, so if it misses a count or two when busy, no big deal.
Pretend it's the mouse on a Macintosh :-)

I also hear that interrupt-on-change will miss interrupts. It's good for a
keyboard wakeup-from-sleep and not much else. Does Andrew Warren have
something on his "answers" page about this? I think so. If you read the
Microchip data sheets _very_carefully_ they actually say so, too.

-Bob

At 08:41 PM 3/3/97 -0800, you wrote:
>        I have been reading the PICLIST for about a month and have seen
several
>methods of doing quadrature decoding on a PIC. One method, the one in the
>Microchip Applications Handbook suggests monitoring one channel and when it
>changes check the other channel to determine direction. Doesn't this reduce
>the resolution of the encoder by half?  This method would be great if it
>didn't because the project I am working on, a six degree of freedom
>trackball, needs to monitor three encoders, and the 16c65 chip I'm using
>only has four interrupt on change pins. However I can't sacrifice
>resolution.
>        BTW, I just wanted to comment on how impressed I am at the
helpfulness(?)
>of everyone on the PICLIST. Keep up the good work!
>
>                                                        Jeff Kroll
>
>

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