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    Date: Thu, 27 Jan 2000  06:46:44
    From: Nikolai Golovchenko <golovchenko@mail.ru>
      To: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
 Subject: Re: pic c compiler
--------------------------------------------------------------------------------

Hello Tom,
      I use one routine all the time and it has always suited me. It
      is called every 20 ms or so and ensures that the button pressing
      causes return of 1 only if two consecutive reads were the same.
      Also, it implements auto-repeat.

      Here it is:

#define KEYPORT PORTA
#define PAUSE   20
#define REPEAT  3
#define KEYMASK 0b00001000      //RA3
static unsigned char Keys;
/****************       KEYS POLLING ROUTINE    *****************
                Low active level assumed
                Should be called every about 20 ms (T)
                PAUSE * T - delay after first click
                REPEAT * T - delay between clicks after
                KEYPORT - PORT register (e.g. PORTA)
                KEYMASK - mask for port register (1 for every button)
                
                Returns TRUE if a key is pressed and on auto-repeat

*/
unsigned char
KeysPoll(void) {
static unsigned char KeysOld;
static unsigned char KeyCnt;
static unsigned char KeyCntLim;

        Keys = KEYPORT; //read port
        if (((Keys ^ KeysOld) & KEYMASK) == 0) {        //Nothing changed
                if (--KeyCnt == 0) {
                        KeyCnt = KeyCntLim;
                        KeyCntLim = REPEAT;
                        KeysOld = Keys;
                        if (((Keys ^ KEYMASK) & KEYMASK) != 0) return 1;
                }
        }
        else {
                KeyCnt = 1;
                KeyCntLim = PAUSE;
        }
        KeysOld = Keys;
        return 0;
}




Bye,
 Nikolai

On Wednesday, January 26, 2000 Tom Weber wrote:
> Hello
> I've got the download version from the ht-soft pic c demo.
> I'm searching for a function, which reads the status of a button/key and
> considers the bouncing. Has someone already written a such function?
> And has already someone realised something with an TDA7318.

> Tom

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