Hi Tim

I've done this many times in C and assembler
I use a timer to sample the switches.
It is very easy to implement.
I set the timer to interrupt every so often and in the ISR I read the port
that has the switch[s].
The port input pin has a 10k or so pull up with a .1 ufd across it (this
rids if of the bulk of the higher freq stuff/arcing. =

 I count the number of times it has been down.
Three (or n depends on the clock speed and how many interrupts you can
handle fewer is better in my mind but you need enough so that a very quick
press ) interrupts or so in a row is a valid down and then I look for an up
to tell me the person has let the go of the switch..
I then push the valid button push into a circular buffer.
In my program when I need to know what/if button s pushed I pull the button
push from the buffer.
If there was no push I get a zero if a button was pushed I get the number
telling which button was pressed for n number of counts and then went up.
I like it because it forces the user to make individual presses of the
button. =


I haven't implemented here yet but you could set a global var in the code
that tells the ISR not to look for the up and to go ahead and push the key
pressed on to the buffer for a valid down.
This would allow the user to hold the key down if he were in a scenario
where he needed to scroll through a long list or inc or dec something with
fine granularity.
I'm going to put this feature in my brightness and contrast control handling
routines
Let me get that in there today and I'll send you the code.
I want to make sure the command buffer doesn't over flow o I will probably
need to change the number of counts while in this mode also.



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Phillip
Things should be as simple as possible but no simpler
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Phillip Coiner
CTO, GPS Source, Inc.
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Your source for quality GNSS Networking Solutions and Design Services, Now!

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Tim Losereith
Sent: Monday, April 03, 2006 3:13 AM
To: piclist@mit.edu
Subject: [PIC] debouncing in c

Hello,

I am looking for an example to debounce several push buttons in c. While =

debouncing the micro shouldn=B4t be blocked by a timer.

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Mit freundlichen Gr=FC=DFen/Best regards,    =

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Tim Losereith


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