#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <avr/pgmspace.h>

unsigned char lcd_digits[10] __attribute__((progmem)) =
{0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x6f};

unsigned char key;
unsigned char data[4]={0,0,0,0};

void actual_data(unsigned int ad)
{
	data[3]=ad%10;
	data[2]=(ad/10)%10;
	data[1]=(ad/100)%10;
	data[0]=(ad/1000)%10;
}

ISR(TIMER0_COMP_vect)
{
	static unsigned char num=0;
	
	PORTC=PORTC&0xf0|1<<num;

	PORTB=pgm_read_byte(lcd_digits+data[num]);

	num++;
	num&=3;
}

void keyboard(void)
{
	static unsigned char row=0;
	static unsigned char p=0;
	char k;

	row++;
	row&=3;

	cli();
	PORTC=(PORTC|0xf0)&~(1<<row+4);
	sei();

	k=PINA|0x0f;

	if(k==0xff)
	{
		p&=~(1<<row);
		return;
	}

	if(p!=0)
		return;

	_delay_ms(10);

	if(k!=(PINA|0x0f))
		return;

	p=0x0f;
	key=row|(k==0xef?0:k==0xdf?1:k==0xbf?2:3)<<2|1<<4;
}

void menu(void)
{
	if(key==0)
		return;

	static unsigned int suma=0;
	suma+=key&0x0f;
	actual_data(suma);

	key=0;
}

int main(void)
{
	DDRB=0xff;
	DDRC=0xff;
	PORTA|=0xf0;

	TCCR0=0x0c;
	OCR0=0x40;
	TIMSK|=1<<OCIE0;
	
	SREG|=1<<SREG_I;

	while(1)
	{
		keyboard();
		menu();
	}

	return 0;
}