#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdio.h>

#define NUM_CHANNELS 4
#define SAMPLE_INTERVAL 1000  // Sample interval in milliseconds

volatile uint16_t adcValues[NUM_CHANNELS];
volatile uint32_t adcSum[NUM_CHANNELS];
volatile uint16_t sampleCount = 0;
volatile uint8_t currentChannel = 0;

void setup() {
    Serial.begin(9600);
    
    ADMUX = (1 << REFS0); // AVcc with external capacitor at AREF pin
    ADCSRA = (1 << ADEN) | (1 << ADIE) | (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // Enable ADC, ADC interrupt, prescaler 128
    
    TCCR1A = 0;
    TCCR1B = (1 << WGM12) | (1 << CS11) | (1 << CS10); // CTC mode, prescaler 64
    OCR1A = 249; // 1 ms interval (16MHz / 64 / 1000 - 1)
    TIMSK1 = (1 << OCIE1A); // Enable Timer1 compare interrupt

    sei(); 
    
    startADC(); // Start first ADC conversion
}

void loop() {
   
}

ISR(TIMER1_COMPA_vect) {
    static uint16_t intervalCount = 0;
    intervalCount++;
    
    if (intervalCount >= SAMPLE_INTERVAL) {
        intervalCount = 0;
        
        for (uint8_t i = 0; i < NUM_CHANNELS; i++) {
            if (sampleCount > 0) {
                uint16_t avgValue = adcSum[i] / sampleCount;
                float voltage = avgValue * (5.0 / 1024.0);
                Serial.print("Channel ");
                Serial.print(i);
                Serial.print(": Average Voltage = ");
                Serial.print(voltage);
                Serial.println(" V");
            }
            adcSum[i] = 0; // Reset sum for next interval
        }
        sampleCount = 0; // Reset sample count for next interval
    }
}

ISR(ADC_vect) {
    uint16_t adcValue = ADC;
    adcValues[currentChannel] = adcValue;
    adcSum[currentChannel] += adcValue;

    currentChannel++;
    if (currentChannel >= NUM_CHANNELS) {
        currentChannel = 0;
        sampleCount++;
    }
    
    startADC(); // Start next ADC conversion
}

void startADC() {
    ADMUX = (ADMUX & 0xF0) | (currentChannel & 0x0F); // Select ADC channel
    ADCSRA |= (1 << ADSC); // Start ADC conversion
}