/*
 * debounce_sw.c
 *
 * Created: 1/20/2018 12:34:11 AM
 *  Author: Islam
 */
#define F_CPU 1000000UL

#include <stdint.h>

#include <avr/io.h>
#include <avr/interrupt.h>

#define SAMPLES_NUM 13
#define UNUSED_BITS ((uint16_t)(0xFFFF<<SAMPLES_NUM))
typedef enum { PRESSED , RELEASED , DE_BOUNCING }SW_ST;

typedef struct
{
    uint16_t samples_mem ;
    SW_ST status ;
    uint8_t samples_count ;
    uint8_t pin_num ;
}SWITCH;

volatile SWITCH sw = {.status = DE_BOUNCING , .pin_num = 3} ;

#define read_pin(PORT,PIN) (PORT & (1<< (PIN)))

#define PULL_UP   1
#define PULL_DOWN 2
#define RESISTOR  PULL_DOWN

void timer_init() ;

int main(void)
{
    DDRA = 0 ;
    DDRC = 0xFF ;
    //PORTA = 0xFF ;
    DDRB = 0xFF ;
    uint16_t x = 0 ;
    timer_init() ;

    uint8_t press_flag = 0 ;

    while(1)
    {
        if(sw.status == PRESSED && !press_flag)
        {
            press_flag = 1 ;
            PORTC++;
        }

        if(sw.status == RELEASED  && press_flag)
        {
            press_flag = 0 ;
            //PORTC = 0 ;
        }

    // PORTB++ ;
    }
}

void timer_init()
{
    OCR0 = 69 ;
    TCNT0 = 0 ;
    /* Pre-scale  = 64 , CTC-mode */
    TIMSK |= (1<<OCIE0) ; // enable timer 0 CTC interrupt

    TCCR0 |= ( 1<<CS00 ) | ( 1<<CS01 ) | ( 0<<CS02 ) | ( 0<<WGM00  ) | ( 1<<WGM01 ) ;

    sei() ;
}

ISR(TIMER0_COMP_vect)
{
    /* 13 samples * 4.4ms = 57.2ms */
    sw.samples_mem = (sw.samples_mem <<1) | (read_pin(PINA,sw.pin_num)>=1) |UNUSED_BITS;

    /*Switch is pressed */
    if(sw.samples_mem == UNUSED_BITS)
    {
        if(++sw.samples_count  == SAMPLES_NUM )
        {
            sw.samples_count =  0 ;
            sw.status =
                      #if RESISTOR == PULL_UP
                        PRESSED ;
                      #else
                        RELEASED ;
                      #endif
        }
    }

    /*Note that status will be 0xFFFF only when switch is released and with 13 identical samples (all 13 samples are high) */
    else if (sw.samples_mem  == 0xFFFF)
    {
       sw.status =
                   #if RESISTOR == PULL_UP
                        RELEASED ;
                      #else
                        PRESSED ;
                      #endif
    }

    else
    {
        sw.status =DE_BOUNCING ;
    }
}