Retriggerbares Monoflop

/* -----------------------------------------------

Retriggerable Monostable

ATtiny13A, 9.6MHz, CKDIV8

PB0 -- Pin 5 ---- MOSI / OC0A

PB1 -- Pin 6 ---- MISO / OC0B / INT0 ---- my Button

PB2 -- Pin 7 ---- SCK

PB3 -- Pin 2 ---- CLKI

PB4 -- Pin 3 ---------------------------- my LED

PB5 -- Pin 1 ---- RESET

------------------------------------------------- */

#define F_CPU 1200000UL  // 9.6MHz/8

#include <avr/io.h>

#include <avr/interrupt.h>

#include <avr/sleep.h>

int8_t a = 0;         // flag

uint8_t k = 0;        // timer overflow count

uint8_t tp = 20;      // output pulse time period in seconds/4, (max 255 = 63.75s)

ISR(INT0_vect) {

   a = 1;

}

ISR(TIM0_OVF_vect) {

   k++;

}

int main(void) {

   DDRB |= (1<<DDB4);                  // output ---------- pin 3

   PORTB &= ~(1<<PORTB4);              // clear output bit

   DDRB &= ~(1<<DDB1);                 // input ----------- pin 6

   PORTB |= (1<<PORTB1);               // pullup

   GIMSK |= (1<<INT0);                 // enable external interrupt on INT0

   TCCR0B |= ((1<<CS02) | (1<<CS00));  // prescaler/1024 (1200000/1024/256 = 4Hz, 0.25s)

   TIMSK0 |= (1<<TOIE0);               // enable timer overflow interrupt

   set_sleep_mode(SLEEP_MODE_PWR_DOWN);

   sei();                              // enable interrupts

   while (1) {

      if(a == 1) {

         PORTB |= (1<<PORTB4);         // set output bit

         a = 0;

         k = 0;

      }

      if(k == tp) {

         PORTB &= ~(1<<PORTB4);        // clear output bit

         a = 0;

         k = 0;

         sleep_enable();

         sleep_cpu();

         sleep_disable();

      }

   }

   return 0;

}