Externer Interrupt 0 am ATMEGA88

#ifndef F_CPU

#define F_CPU 1000000UL //factory default clock value

#endif

#include <avr/io.h>

#include <avr/iomx8.h>

#include <avr/interrupt.h>

#include <stdint.h> /** unsigned data types */

/** struct for setting single port bits

source: [http://www.mikrocontroller.net/attachment/27445/SBIT.C] */

struct bits {

uint8_t b0:1;

uint8_t b1:1;

uint8_t b2:1;

uint8_t b3:1;

uint8_t b4:1;

uint8_t b5:1;

uint8_t b6:1;

uint8_t b7:1;

} __attribute__((__packed__));

#define SBIT(port,pin) ((*(volatile struct bits*)&port).b##pin)

/** ports for incremental encoder, inputs */

#define VOL_A SBIT( PIND, 1 ) /** incremental encoder output A */

#define VOL_B SBIT( PIND, 2 ) /** incremental encoder output B */

#define DDRD_SETTING 0x00 /** Port D direction setting iiii_iiii */

void init_ports(void)

{

    DDRD = DDRD_SETTING;

    EICRA |= 0x03;  /** set external interrupt 0 at rising edge */

    EIMSK |= 0x01;  /** activate external interrupt 0 */

    EIFR |= 0x01;  /** activate execution of interrupt 0 */

}

void init_timer(void)

{

    TCCR0A |= 0x02;  /** set CTC mode */

    TCCR0B |= 0x04;  /** set prescaler to 256 */

    OCR0A = 39;  /** at 1 MHz clock: (1000000 Hz)/ 256 / (100 Hz) = 39 counter tics */

    TIMSK0 |= 0x02;  /** activate timer compare match A interrupt */

}

int main(void)

{

    init_ports();

    init_timer();

    sei();  /** global enabling of interrupts */

    while(1)

    {

        //TODO:: Please write your application code

    }

}

ISR (TIMER0_COMPA_vect)

{

    … /** code der ausgeführt wird */

}

ISR (INT0_vect) /** interrupt is activated at rising edge of VOL_B */

{

    if(VOL_A)  /** clock wise turn */

        get_volume(1,0);  /** increase volume */

    else  /** VOL_A is 0, counter clock wise turn */

        get_volume(-1,0); /** decrease volume */

}