mouldy.org

#include < avr/io.h>

void delay_ms(unsigned char ms)
/* badly mangled delay_ms */
{
	unsigned short outer1, outer2;
     	outer1 = 1; 

    	while (outer1) {
		outer2 = 1000;
		while (outer2) {
			while ( ms ) ms--;
			outer2--;
		}
		outer1--;
	}
}

int main(void)
{
	/* enable  PD5 as output */
	DDRD |= 1 << PD5;

	unsigned char bright = 0;
	char up = 1;

	TCCR1A |= 1 << COM1A1; // clear OC1A/OC1B on compare match during upcount; set on match during downcount
	TCCR1A |= 1 << WGM10; // PWM, phase correct, 8-bit
	TCCR1B |= 1 << CS10; // internal clock, 1:1 prescale
	while (1) {
		delay_ms(0);
		TCNT0 = 0;

		if (up)
			++bright;
		else
			--bright;
		
		OCR1A = bright;

		if (bright == 255)
			up = 0;
		if (bright == 0)
			up = 1;
	}
	return 0;
}