Atmega8 LCD thermometer

termometr.c

#include <avr/io.h>
#include <avr/pgmspace.h>
#include "lcd.h" // HD44780U LCD library, Peter Fleury
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <stdbool.h>

#define F_CPU 1000000

void iprint(int n)
{
	if( n > 9 )
	{ int a = n / 10;

		n -= 10 * a;
		iprint(a);
	}
	lcd_putc('0'+n);
}

void lcd_putnum(int n, bool decimal_point){

	if (n<0) {
		lcd_putc('-');
		n=-n;
	}
	
	if (decimal_point){
		iprint(n/10);
		lcd_putc('.');
		iprint(n%10);
	} else iprint(n);
			

}



const int16_t values[] PROGMEM = {4078,3122,2600,2241,1965,1741,1550,1382,1232,1095,969,850,737,629,
524,423,323,224,125,25,-76,-179,-287,-399,-519,-649,-793,-957,-1155,-1414,-1816};


int adc2temp(int x){
	
	const int min=32;
	const int step=32;
	int i, y1, y0, x0;

	if ( (x>=min) && (x<=min+step* (sizeof(values)/sizeof(int16_t) - 1) ) ){
		i=(x-min)/step;

		y1 = (int16_t)pgm_read_word( &values[i+1] );
		y0 = (int16_t)pgm_read_word( &values[i] );
		x0=min+step*i;
		return ( y0 + ( (y1-y0) * (x-x0) ) / step ) / 4;
	} else return -9999;
}




ISR (TIMER0_OVF_vect)  // timer0 overflow interrupt
{
	cli();
	ADCSRA |= (1<<ADSC);
	sei();
}

ISR (ADC_vect){
	cli();
	int temp;
	temp=adc2temp(ADC);
	lcd_gotoxy(0,0);
	lcd_putnum(temp, true);
	lcd_puts(" | ");
	lcd_putnum(ADC, false);
	lcd_puts("    "); // potrzebne na wypadek gdy wcześniejszy napis był krótszy niż obecny
	sei();
}



int main(void)
{

	/* initialize display, cursor off */
	lcd_init(LCD_DISP_ON);

	TCCR0 |= (1 << CS02) | (1 << CS00);
	// set prescaler to 1024 and start the timer

	TIMSK |= (1 << TOIE0);
	
	ADMUX |= (1 << REFS0) | (1 << MUX2) | (1 << MUX0); //adc5 - pin 28, ref=avcc
	
	ADCSRA=(1<<ADEN)|(1<<ADIE)|(1<<ADPS0)|(1<<ADPS1)|(1<<ADPS2);
	
	sei();
	
	
	
	while(1) {
		//set_sleep_mode(SLEEP_MODE_IDLE);
		//sleep_enable();
	}
	// zatrzymujemy CPU, cała reszta działa i wybudza przerwaniami




}