> Someone once posted a very elegant technique (or at least I thought
> so). In each interrupt (since you know they'll be coming regularly)
> read the state of the switch. Then rotate it into a register. In your
> mainline you'll be comparing that register to a constant to determine
> a button press. If you're rotating from right to left, you might want
> to look for '11110000' which would represent 40ms of button pressed
> followed by 40ms of button released.

Not elegant enough, alas.
That only works for a fully debounced signal.
eg if, shifting left, you got

             11010000

You would never get your 11110000 trigger pattern while having passed a 
valid edge.

What would be valid is, for a 0 to 1 transition, to look for eg

    xxxx1111

which would happily allow 00001111, 00101111, 01101111 etc

but you could as easily just increment a counter on every "1", reset it on 
every 0, and look for a count of 4 (in this case).

The shifting method may be somewhat quicker than a counter.


    Russell


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