/*
 * PulseGen.c
 * 21KHz
 * Created: 02.05.2020 19:47:32
 * Author : Osman Mazinov
 */
#ifndef F_CPU
    #define F_CPU 9600000L
#endif
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#define PULSE PINB4
 
void mcu_init(void);
 
ISR(TIM0_OVF_vect)
{
    // Predivider  256 
    // 9,6 / 256 / 2000 = 19
    // 256 - 19 = 238 = EE
    TCNT0 = 0xE6;
    PORTB ^= (1<<PULSE);
}
 
int main(void)
{
    mcu_init();   
     
    while (1) {
 
    }
}
 
 
void mcu_init(void) {
     
    //Crystal Oscillator division factor: 1;
    #pragma optsize-
    CLKPR=(1<<CLKPCE);
    CLKPR=(0<<CLKPCE) | (0<<CLKPS3) | (0<<CLKPS2) | (0<<CLKPS1) | (0<<CLKPS0);
    #ifdef _OPTIMIZE_SIZE_
    #pragma optsize+
    #endif
     
    //Input/Output Ports initialization;
    //Port B initialization;
    DDRB |= (1<<DDB4);
    // State: Bit5=T Bit4=P Bit3=1 Bit2=T Bit1=P Bit0=T;
    PORTB |= (0<<PORTB4);
     
    // In order for the first overflow interrupt to occur
    // the counter must be reset to zero here as well.
    TCNT0 = 0xE6;
     
    // Frequency divider ratio 8
    TCCR0B |= (1 << CS01); //(1 << CS02); // | (1 << CS00);
     
    // Enable counter fill interrupt
    TIMSK0 |= (1 << TOIE0);
     
    // Enable global interrupt
    sei();
}