Please get rid of you private REPLY address to that default replies go to
the list.

>    Schmitt Trigger is a thing to construct with a bounceless input
> by hardware design. I've attached a .jpg with it. May be I'm wrong?
>    What is the sense in programmatic debouncing with a Schmitt
> Trigger. Is not it enough simply to desable interrupt while interrupt
> handling?

Your circuit will work *IF*:

1 - The switch is SPDT as you showed.

2 - The switch performs break before make.

3 - The voltage resulting from the resistor divider when the switch is
completely open is guaranteed to be within the hysterisis dead band of the
schmitt trigger input.

That's a lot of IFs, particularly the one about needing a SPDT switch.  This
discussion had to do with the more normal low cost SPST switch to ground
with a passive pullup to power.  If using port B with internal pullups
enabled, this requires no other parts than the switch itself.  This scheme
does, however, require software debouncing if you are trying to resolve both
the press and release states.


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