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

void init_display();
void init_timer0();
void init_timer2();
void init_ADC();

volatile uint8_t lcdx=0, lcdy=0; 
const char lcdcmd[2] = {0xC0, 0x80};
unsigned char LCDline[2][16]={{"ADC         0x00"},
                              {"PWM           CW"}};

const char LookUp[16] ={"0123456789ABCDEF"};

int main(void)
{    
	uint8_t result;
	
    init_display();
    init_timer0();  // initialize timer0
	init_timer2();  // initialize timer2
    init_ADC();
    
    sei();  // enable global interrupts
    // loop forever    
    while(1)
    {
		ADCSRA |= (1<<ADSC);
		while((ADCSRA&(1<<ADSC))==(1<<ADSC));
		result = ADCH;
		if (result<128) {
			OCR2A = 2*(127-result);
			PORTB = (PORTB&0xFC)|0x01;
			LCDline[1][13] = 'C';
		}
		else
		{
			OCR2A = 2*(result-128);
			PORTB = (PORTB&0xFC)|0x02;
			LCDline[1][13] = ' ';
		}
		LCDline[0][14] = LookUp[(result&0xF0)>>4];
		LCDline[0][15] = LookUp[(result&0x0F)];
		_delay_ms(1000);
    } // while(1)
}

void init_display()
{
    DDRA = 0xFF;
    
    PORTC &= 0xAF;
    DDRC  |= 0x50;
    
    PORTC &= 0xBF;

    PORTA = 0x38;
    PORTC |= 0x10;
    PORTC &= 0xEF;
    PORTA = 0x0C;
    PORTC |= 0x10;
    PORTC &= 0xEF;
    PORTA = 0x01;
    PORTC |= 0x10;;
    PORTC &= 0xEF;  
    _delay_ms(2);
}

void init_ADC()
{
	ADMUX = (1<<REFS0)|(1<<ADLAR);	// AVCC, left align, MUX ch 0
	DIDR0 |= (1<<ADC0D);			// disable digital input
	ADCSRA = (1<<ADEN);				// enable ADC
}

void init_timer0()
{
    TCCR0B |= (1<<CS02)|(1<<CS00);	// prescaler 1024
    TCNT0 = 0;			            // initialize counter
    TIMSK0 |= (1 << TOIE0);	        // enable overflow interrupt 
}

void init_timer2()
{
	DDRB |= (1<<DDB4)|		// OC2A output
			(1<<DDB1)|		// CCW
			(1<<DDB0);		// CW
	
	PRR0 &= ~(1<<PRTIM2);	// disable power saving
	
	TCCR2A = (1<<COM2A1)|
	         (0<<COM2A0)|	// non-inverting mode
	         (0<<WGM22) |
			 (1<<WGM21) |
			 (1<<WGM20);	// Fast PWM mode 3
	TCCR2B = (1<<CS22)|		      
			 (0<<CS21)|
			 (0<<CS20);	// prescaler 64 PWM freq 16Mhz/256/64 = 977Hz
			  
	OCR2A = 0x00;
}

ISR(TIMER0_OVF_vect)
{
    if(lcdx==16) {
        PORTC &= 0xBF;
        PORTA = lcdcmd[lcdy];
        lcdx = 0;
        lcdy = 0x01 & (lcdy+1);
    }
    else {
        PORTC |= 0x40;
        PORTA = LCDline[lcdy][lcdx];
        PORTC |= 0x10;
        lcdx++;
    }
    PORTC |= 0x10;
    PORTC &= 0xEF;
}