#include <avr/io.h>

#define get_bit(reg,bitnum) ((reg & (1<<bitnum))>>bitnum)

int main(void)

{

   DDRD=0b11111000; // set the first 3 pins of PORTD to be inputs to read from the push buttons

    DDRB=0b11111111; // ensure that Pin3 in POrt B is output as this is the OC0 pin that wll produce the PWM.

    PORTD=0b00000000; // Initialize PORTD to zeros

    TCCR0=0b01110101; //Configure TCCR0 as explained in the article

    TIMSK=0b00000000;

    OCR0=255; // Set OCR0 to 255 so that the duty cycle is initially 0 and the motor is not rotating

       while(1)

    {

       if (get_bit(PIND,0)==1)

       {

              OCR0=178; //If button 1 is pressed, set OCR0=178 (duty cycle=10%).

       }

       if (get_bit(PIND,1)==1)

       {

              OCR0=102; //If button 2 is pressed, set OCR0=102 (duty cycle=60%).

       }

       if (get_bit(PIND,2)==1)

       {

              OCR0=25; //If button 3 is pressed, set OCR0=25 (duty cycle=90%).

       }      }  }