f_10_24_sw_debounce.c

* Use 10 MHz crystal frequency. * Use Timer0 for ten millisecond looptime. * Blink "Alive" LED e

#include "config.h"
#include "delay.h"
#include "serial.c"
#include "serio.c"

// switch debounce with timer2

#define DEBOUNCE  5
volatile unsigned char button, button_debounce;


#if defined(HI_TECH_C)
void interrupt pic_isr(void)
#endif
#if defined(__18CXX)
#pragma interrupt pic_isr
void pic_isr(void)
#endif
{
  if (INT2IF && INT2IE) {
    // pushbutton detected
    // disable interrupt, set semaphore
    INT2IE = 0;  button = 1;  button_debounce = 0;
  }
  if (TMR2IF) { // debouncing timer
    TMR2IF = 0;
    if (!INT2IE) {
      if (RB2) { 
       if (button_debounce != DEBOUNCE) button_debounce++;  
      } else  button_debounce=0; 
      if (button_debounce == DEBOUNCE && !button){
	//button idle high ,re-enable interrupt
	INT2IF=0; INT2IE=1;
      }
    }
  }
}

void main(void){
  serial_init(95,1); // 19200 in HSPLL mode, crystal = 7.3728 MHz
  button = 0; button_debounce = 0;
  // configure INT2 for falling edge interrupt input
  TRISB2 = 1;  INT2IF = 0; INTEDG2 = 0;  INT2IE = 1;
  RBPU = 0; // enable weak pullup on port B
  // configure timer 2
  // post scale of 11, prescale 16, PR=250, FOSC=29.4912 MHz 
  // gives interrupt interval of ~ 6 ms
  TOUTPS3 = 1; TOUTPS2 = 0; TOUTPS1 = 1; TOUTPS0 = 0;
  T2CKPS1 = 1;  PR2 = 250;  
  // enable TMR2 interrupt
  IPEN = 0;  TMR2IF = 0; TMR2IE = 1;   PEIE = 1;  GIE = 1;
  TMR2ON = 1 ;
  pcrlf();  printf("Pushbutton with Timer2 Debounce");  pcrlf();
  while(1) {
    if (button) {
      button=0; // consume this semaphore
      printf("Push Button activated!"); pcrlf();
    }
  }//end while
}//end main

//for MCC18, place the interrupt vector goto
#if defined(__18CXX)
#if defined(HIGH_INTERRUPT)
#pragma code HighVector=HIGH_INTERRUPT
#else
#pragma code HighVector=0x0008  
#endif
void HighVector (void)
{
    _asm goto pic_isr _endasm
}
#pragma code
#endif