#include "header.h"

// Table 14-6. Port C Pins Alternate Functions
// - PC0 -> ADC0 (ADC Input Channel 0)
//       -> PCINT8 (Pin Change Interrupt 8)
//
// 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL
//
// START A CONVERSTION in single conversion mode :
// - disabling the Power Reduction ADC bit, PRADC
// - writing a logical one to the ADC Start Conversion bit, ADSC

#define ADC_PRESCALER	8

void adc_init() {
    ADMUX = (1 << REFS0);						// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
    ADCSRA = (1 << ADEN) 						// 24.9.2 : enable ADC
           | ADC_PRESCALE_SET(ADC_PRESCALER);	// Table 24-5 : prescaler ADC
}

uint16_t adc_read(uint8_t channel) {
	CLEAR(PRR, PRADC);							// 24.3 : ensure power reduction is disabled for ADC, (10.11.3 : PRR – Power Reduction Register)
    ADMUX = (ADMUX & 0xF0) | (channel & 0x0F);	// Select ADC channel
    ADCSRA |= (1 << ADSC);						// 24.9.2 : Start conversion, ADSC: ADC Start Conversion
    while (ADCSRA & (1 << ADSC));				// Wait for completion
    return ADC;
}