PWM-LED-ADC-Discrete.c

/*
 * PWM-LED-ADC-Discrete.c
 *
 * Created: 09-12-2014 23:44:18
 *  Author: sidj
 
 This code works on an ATMega 16/32 microcontroller with an external crystal of frequency 16MHz attached to it.
 The LED is connected to the PB3 of the microcontroller which is the default PWM output for Timer 0.
 The ADC is taken on PA0
 */ 

#include <avr/io.h>
#define F_CPU 16000000UL
#include <util/delay.h>

int main(void)
{
	DDRA=0;
	DDRB=255;
	PORTB=(1<<PB3);
	int a;
	
	ADMUX|=(1<<REFS0);     //internally shorting AREF and AVCC   //analog signal taken on pin0
	ADCSRA|=(1<<ADEN)|(1<<ADPS0)|(1<<ADPS1)|(1<<ADPS2);  //enabling ADC and setting division factor
	TCCR0|=(1<<WGM01)|(1<<WGM00)|(1<<COM01)|(1<<CS00);     //setting on fast PWM mode and no prescaling
	
    while(1)
    {
		ADCSRA|=(1<<ADSC);
		while((ADCSRA & (1<<ADSC)) !=0);
		a=ADC;
		
		if (a<=409)                  //for analog voltage less than 2volts// 
		{
		OCR0=64;  //25% duty cycle
		}
		else if((a>410)&&(a<=613)){        //analog voltage between 2 to 3 volts//
		OCR0=128; //50% duty cycle
		}			
		else if((a>613)&&(a<=818))    //analog voltage between 3 to 4 volts// 
		{
		OCR0=192; //75% duty cycle
		}
		else if(a>818) //else between 4-5 volts//
		{
		OCR0=254; //~100% duty cycle
		}				
		
    }
}