#include "header.h"

// 24.2 : The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and ADCL

void adc_init(uint8_t prescaler_value) {
    ADMUX = (1 << REFS0);									// Table 24-3 : set voltage reference, AVCC with external capacitor at AREF pin
	ADMUX |= (1 << ADLAR);									// 24.9.1 : result is left adjusted, meaning the first 8 bits values are readable in ADCH, (24.9.3.2 : ADC data register is not updated util ADCH is read)
    ADCSRA = (1 << ADEN); 									// 24.9.2 : enable ADC
	ADCSRA |= (1 << ADATE); 								// 24.9.2 : enable Auto Trigger -> it will start a conversion on the selected channel in ADMUX when the selected source (in ADCSRB) is triggered
	ADCSRA |= (1 << ADIE);								 	// 24.9.2 : enable ADC Interrupt
    ADCSRA |= ADC_PRESCALE_SET(prescaler_value);			// Table 24-5 : prescaler ADC

	ADCSRB = ADC_TRIGGER_TIMER_1_COMPARE_B;					// Table 24-6 : ADC Auto Trigger Source
	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select ADC channel 0
}

void adc_print_hex(uint8_t value) {
	char buffer[3] = {0};
	int_to_hex_string(value, buffer, 2);
	uart_printstr(buffer);
}

ISR(ADC_vect) {												// Table 12-6 : interrupt vector for ADC Conversion Complete
	uint8_t value = ADCH;									// 24.9.3.2 : read ADCH 8 bits precision
	adc_print_hex(value);

	// loop through channel
	adc_channel = (adc_channel + 1) % 3;					// loop through channels
	ADMUX = (ADMUX & 0b11110000) | (adc_channel & 0b1111);	// Table 24-4 : Select next ADC channel
	if (adc_channel != 0) {
		uart_printstr(", ");
		ADCSRA |= (1 << ADSC);								// 24.9.2 : start next conversion
	} else {
		uart_printstr("\r\n");
	}
}