> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Rikard Bosnjakovic
> Sent: 01 April 2009 18:33
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] One button, three purposes
> 
> On Wed, Apr 1, 2009 at 19:11, Michael Rigby-Jones
> 
> > Just to clarify, are you using the overflow counter to check how
long
> > the button is pressed,
> 
> Correct. The overflow-variable counts the Timer0-overflows (which
> starts counting as soon as the button/RA0 is pressed).
> 
> > so a short press starts or stops the timer, and a
> > long press resets it?
> 
> Yes, this is my intention which I'm unsuccessfull with. To clarify
> even more: "timer" here means Timer1 (external 32kHz-crystal).


For this example it might be easier to check the button in the interrupt
handler e.g. in pseudo code:

' main loop
do
    if short_press = 1 then
        ' toggle timer state
        TMR1ON = 1 ^ TMR1ON
        
        ' short press now serviced
        short_press = 0
    end if

    if long_press = 1 then
        ' is timer running?
        if TMR1ON = 0 then
            ' timer not running so reset it
            TMR1H = 0
            TMR1L = 0
        end if
        
        ' long press now serviced
        long_press = 0
    end if

loop



interrupt:
    ' button pressed
    if RA0 = 1 then
        overflows = overflows + 1

        if overflows = 50 then
            ' flag a long button press
            long_press = 1
        else if overflows > 50 then
            ' stop overflow counter rolling over
            overflows = 51
        end if

    ' button released
    else
        ' test for short press
        if (overflows > 0) AND (overflows < 5) then
            short_press = 1
        end if
        ' reset overflow counter
        overflows = 0
    endif


If the button press length isn't critical, you may be able to optimise
the interrupt by checking individual bits within the overflow counter
variable e.g. if bit 6 is set that means 64 over flows and a long press,
if bit 7 is set then stop incrementing counter etc.


Hope that helps

Regards

Mike

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