#include <avr/io.h>
#include <avr/interrupt.h>

#define F_CPU 8000000

#define USART_BAUDRATE 9600
#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)

void main(void)
{

UCSRB |= (1 << RXEN) | (1 << TXEN);  // Turn on the UART
UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);  // Use standard 8N1
UBRRL = BAUD_PRESCALE; 	       // Load lower 8-bits of the baud rate value
                               // into the low byte of the UBRR register
UBRRH = (BAUD_PRESCALE >> 8);  // Load upper 8-bits of the baud rate value
                               // into the high byte of the UBRR register

TIMSK |= (1 << TOIE1);	       // Enable Timer1 overflow interrupt
TCCR1B |= (1 << CS11);	       // Turn on Timer1, CLK/8 prescale

ADMUX |= (1 << REFS0);	       // Select VCC reference
ADMUX |= (1 << ADLAR); 	       // Left adjust ADC result
ADCSRA |= (1 << ADEN) | (1 << ADIE);    // Turn on ADC and enable
                                        // conversion complete interrupt
ADCSRA |= (1 << ADPS1) | (1 << ADPS2);	// ADC prescale of CLK/64

sei();

while(1); {}

}

ISR(TIMER1_OVF_vect)
{

ADCSRA |= (1 << ADSC);	       // Start ADC conversion

}

ISR(ADC_vect)
{
unsigned long VOLTAGE = ((((ADCH/10)+((ADCH/100)*6))*16)+(ADCH%10));

unsigned int ONES = 0x00;
unsigned int TENS = 0x00;
unsigned int HUND = 0x00;

if((VOLTAGE & 0x0800) == 0x0800) HUND |= 0x08; else HUND &= ~0x08;
if((VOLTAGE & 0x0400) == 0x0400) HUND |= 0x04; else HUND &= ~0x04;
if((VOLTAGE & 0x0200) == 0x0200) HUND |= 0x02; else HUND &= ~0x02;
if((VOLTAGE & 0x0100) == 0x0100) HUND |= 0x01; else HUND &= ~0x01;

if((VOLTAGE & 0x0080) == 0x0080) TENS |= 0x08; else TENS &= ~0x08;
if((VOLTAGE & 0x0040) == 0x0040) TENS |= 0x04; else TENS &= ~0x04;
if((VOLTAGE & 0x0020) == 0x0020) TENS |= 0x02; else TENS &= ~0x02;
if((VOLTAGE & 0x0010) == 0x0010) TENS |= 0x01; else TENS &= ~0x01;

if((VOLTAGE & 0x0008) == 0x0008) ONES |= 0x08; else ONES &= ~0x08;
if((VOLTAGE & 0x0004) == 0x0004) ONES |= 0x04; else ONES &= ~0x04;
if((VOLTAGE & 0x0002) == 0x0002) ONES |= 0x02; else ONES &= ~0x02;
if((VOLTAGE & 0x0001) == 0x0001) ONES |= 0x01; else ONES &= ~0x01;

ONES |= 0x30;
TENS |= 0x30;
HUND |= 0x30;

UDR = HUND;				// Send the ADC results to the UART
while ((UCSRA & (1 << UDRE)) == 0) {}; 	// Wait for UDR to clear
UDR = TENS;
while ((UCSRA & (1 << UDRE)) == 0) {};
UDR = ONES;
while ((UCSRA & (1 << UDRE)) == 0) {};
UDR = 0x0D;				// Send new line
while ((UCSRA & (1 << UDRE)) == 0) {};
UDR = 0x0A;

}