ATtiny 5/10: Read ADC2 (PB2) and output servo PWM signal on PB0 and PB1

main.c

/*
  Read ADC2 (PB2) and output servo signal on PB0 and PB1.
  ATtiny5 or 10 at default 1MHz.
 */

#include <avr/io.h>

int main(void)
{
    // ADC channel 2
    ADMUX = 2;
    // Disable digital input on PB2
    DIDR0 = (1<<ADC2D);
    // Enable ADC, presc 1:8 for 125kHz ADC-clock
    ADCSRA = (1<<ADEN) | (1<<ADPS1) | (1<<ADPS0);

    // PB0 and 1 output.
    DDRB = (1<<PB0) | (1<<PB1);

    // Timer0 50Hz PWM, 1us tick, mode 14 with ICR0 as TOP.
    ICR0 = 19999; // 1MHz / 50Hz - 1
    // Start with 1.5 ms pulse-width
    OCR0A = OCR0B = 1500;

    // OC0A and OC0B non inverting PWM, mode bit 1
    TCCR0A = (1<<COM0A1) | (1<<COM0B1) | (1<<WGM01);
    // mode bits 2 and 3, presc 1:1
    TCCR0B = (1<<WGM03) | (1<<WGM02) | (1<<CS00);
    

    while(1)
    {
	uint8_t i;
	uint16_t adc4;

	// Take four ADC samples, add them in adc4
	for (i = 0, adc4 = 0; i < 4; i++)
	{
	    // Start a conversion
	    ADCSRA |= (1<<ADSC);
	    // wait until it's finished
	    while (ADCSRA & (1<<ADSC))
		; // Nothing
	    adc4 += ADCL;
	}

	// Set PWM to 990 to 2010 ms from ADC.
	OCR0A = 990 + adc4;
	// OCR0B "inverted" servo signal
	OCR0B = 2010 - adc4;
    }
}