Justin,

I know your mention of hardware is actually for the switch to generate an
interrupt but, would you consider a NAND gate latch setup? Or is this too
much or unnecessary hardware? I've build a sample circuit like this before
but I've never tested its resiliency with a range of switches that have
varying debounce times. Any information I've gathered from this approach has
not pointed to this being a "better" solution.

Unfortunately, I need this to be as robust as possible and with the solution
being through software, I could at least "tune" the debounce if switches are
chosen outside a comfortable range.

I'm in the investigation phase right now and I'm using some simple SPST,
normally open, momentary switches - I will ultimately move this to a setup
that is rubber keypad/PCB contact assembly, for which I really appreciate
the note from Paul Webster on switch/key design - that was great.

-DO


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Justin Crooks
> Sent: Monday, April 12, 1999 3:53 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Newbie Toggle Switch Woes
>
>
> I find this to be overkill.  I design the hardware to interrupt on
> keypress.  I start the timer, and when the timer is done, I read the
> keypress.  I use a keypad that gurantees debounce time <10 ms, which makes
> life about as easy as can be.  I then wait until the key is definitely
> released before allowing another to be read.  About as simple as can be.
>
> I guess it depends how robust your application needs to be... adjust your
> code accordingly.
>
> ----------
> > From: Andy Kunz <mtdesign@FAST.NET>
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: Newbie Toggle Switch Woes
> > Date: Monday, April 12, 1999 10:00 AM
> >
> > >Anybody have a favorite debouncing scheme?
> >
> > I use TMR0 to debounce.  I only test the switch after "n" TMR0
> overflows,
> > and only count the state as changed after it has been consistently in
> that
> > state for "y" times.
> >
> > You want to set it up so you get at least 3 samples over a 10-30mS
> period.
> >
> > Andy
>