Thanks Bob,

things becoming complicated. it sounds like doable but also becomes complic=
ated too.
use CNI interrupt as a state machine then change the state as soon as hit a=
ny key=A0
after let's say 100 scan disable timer base routine. what if while disablin=
g they press
another key you are going to have missing number. I do not know I have to t=
hink
but it's a good idea

thanks


AA=A0


________________________________
From: Bob Blick <bobblick@ftml.net>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
Sent: Thursday, October 6, 2011 1:24 PM
Subject: Re: [PIC]: keypad debounce issue

On Thursday, October 06, 2011 10:57 AM, "Andre Abelian"=A0 wrote:

> I am reading a keypad that is connected to other board. I am using
> PIC24FJ256GB110
> with CCS PICC compiler. I am using CNI interrupt "port on change" and
> connetced to all 4 rows.
> any time any row goes low it create interrupt but also when it goes high
> creates interrupt too.
> the problem I am having is that I am getting duplicated key "debounce
> issue". Normally=A0

Hi Andre,

Normally I just scan the keyboard every 20 to 50 milliseconds.

Two reasons why I would use interrupt-on-change:

1) I'm saving power in sleep mode and use it to wake up.
2) I want immediate response to a keypress (fire a weapon?)

But I would only use the interrupt to trigger a recurring scan. I would
have a recurring timer that would do the actual scans. Only one would be
enabled at a time. After a number of scans with no keypress, I would
enable the interrupt-on-change and disable the timer-based scanning.

Cheerful regards,

Bob

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