/* ******************************************************** *
 *
 * Simple program with avr-gcc and ATtiny13
 * -------------------------------------------------------- *
 * Created on: 	07.06.2016
 * Author:		Paolo Iocco
 * ******************************************************** */
/* ******************************************************** *
    ATtiny 13/45/85 Pin map
                           +--\/--+
         /Reset ADC0 PB5  -|1°   8|-  Vcc
                ADC3 PB3  -|2    7|-  PB2 ADC1 SCK
                ADC2 PB4  -|3    6|-  PB1 OC0B MISO AIN1
                     GND  -|4    5|-  PB0 OC0A MOSI AIN0
                           +------+
* ********************************************************* */

#include "main.h"

void adc_setup (void)
{
    // Set the ADC input to PB2/ADC1
    ADMUX |= (1 << MUX0);
    ADMUX |= (1 << ADLAR);
    // Set the prescaler to clock/128 & enable ADC
    ADCSRA |= (1 << ADPS1) | (1 << ADPS0) | (1 << ADEN);
}

int adc_read (void)
{
    // Start the conversion
    ADCSRA |= (1 << ADSC);
    // Wait for it to finish
    while (ADCSRA & (1 << ADSC));
    return ADCH;
}

void pwm_setup (void)
{
	// Set Timer 0 prescaler to clock/8.
	// At 9.6 MHz this is 1.2 MHz.
	TCCR0B |= (1 << CS01) | (1 << CS00);
	// Set to 'Fast PWM' mode
	TCCR0A |= (1 << WGM01) | (1 << WGM00);
	// Clear OC0B output on compare match, upwards counting.
	TCCR0A |= (1 << COM0B1);
}

void pwm_write (int val)
{
    OCR0B = val;
}

int main (void)
{
    int adc_in;
    // LED is an output.
    DDRB |= (1 << LED);
    adc_setup();
    pwm_setup();
    while (1) {
        // Get the ADC value
        adc_in = adc_read();
        // Now write it to the PWM counter
        pwm_write(adc_in);
    }
}