----- Original Message -----
From: Mccauley, Daniel H <daniel.h.mccauley@LMCO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, May 20, 2003 2:54 PM
Subject: Re: [PIC]:Pushbutton Timing Routines Was: IDEAS for Pushbutton M
ode Selections


> I came up with the following routine for the following.  Let me know what
> you think.
> If the pushbutton is pressed and released less than 2 seconds, the program
> runs MODE1 and if the button is held for
> greater than 2 seconds, SET-UP mode is run
>
>
> char count;
> count=0;
> if (input(PB1)==0)
>         {
>         delay_ms(20);           // Simple Debounce
>         while (input(PB1)==0)
>                 {
>                 count++;
>                 delay_ms(10);
>                 }
>         if (count < 200)
>                 RunMode1 ();
>         else
>                 SetUpMode ();
>         }
>
> Anyone see any problems (debouncing etc...) with this simple routine???
> Thanks much.
>
> Dan
>

Hi Dan,
As Dale has already pointed out the count only being 8 bits wide would give
you problems. I would suggest a further refinement:

         while (input(PB1)==0  &&  count < 200)
         {
                 count++;
                 delay_ms(10);
          }

         if (count < 200)
         {         RunMode1 ();
         }
         else if (count > 3)
         {        SetUpMode ();
         }

Also note that if the switch is not released before this section of code is
encounted again you may get a false trigger to RunMode1 or SetUpMode. You
should be looking for a "switch released" somewhere.

You might like to take a look at
http://www.xcprod.com/titan/XCSB/CONTRIB/lcd-04.bas This does switch
debouncing in a seperate user task and greatly simplifies dealing with
switch events and timing contraints involving multiple switches complex
states.

Regards
Sergio Masci

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