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

int main(){
	ADMUX=0x40; 
	DDRD=0xff;
	DDRB=0xff;
	while (1){
		long k=0;
		unsigned char lowc, highc;
		unsigned short c, threshlow=250, threshhigh=500;
		unsigned char d;
		ADCSRA=0xc0;
		for (k=0;k<50;k++);
		lowc=ADCL; // 8 low bits
		for (k=0;k<30;k++);
		highc=ADCH; // 2 high bits; must sample both low and high
		            // higher unused bits are reliably zero always
		c = 256*highc + lowc; // 0..1023
		// c = c>>2; // keep 2 high bits and 6 low bits
		if (c > threshhigh) d=0xff;
		if (c < threshlow) d=0x00;
		PORTD=d;
	}
}