> debouncing even with SPST switch (Jinx are you on-line?)

Yes, I are

> It contains a dozen of buttons, the same quantity of lamps
> and a couple of simple devices to be switched on or off

Aaaahhh. An activity centre, how cute. I'm sure it will keep
you amused for absolutely hours

> So I have 3 loops where I have to choose polling or interrupt
> driven technique.

It's hard to generalise. It depends on what resources you have
and how much spare time they have. For example, I'm working
on something that has RS232 as the first priority (as I can't re-
request the data). Everything else has to fit in around that. It
could get messy breaking out of a serial routine to service an
interrupt from a not-very-important event that could have waited.

Event occurrences can be held in flags without causing an
interrupt, and can be polled at will. You could also store
external transients in a simple sample-hold using R D & C

Don't know if this is possible with your set-up, but I've used
parallel-serial registers to store pushbutton presses and toggle
switche changes. Kind of like scanning a keyboard matrix but
you do it with serial data

Break it down in terms of worst-case timing. What could you
miss, how could you fix that, etc etc

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