unsigned char *TCCR0A_ESP = (unsigned char *)0x2A;
unsigned char *TCCR0B_ESP = (unsigned char *)0x2B;

void MyDelay(unsigned long mSec);

void init_PWM() {
    // Set OC0A (PD6) as output
    unsigned char *portPinD;
    portPinD = (unsigned char *) 0x29;
    *portPinD |= 0x40;
    // Configure Timer/Counter 0 for Fast PWM
    *TCCR0A_ESP |= 0x23;
    *TCCR0A_ESP |= 0x80; // Set OC0A on compare match, clear OC0A at BOTTOM
    *TCCR0B_ESP |= 0x01; // No prescaler
}

void init_ADC() {
    // Set A0 (PC0) as input
    unsigned char *portPinC;
    portPinC = (unsigned char *) 0x26;
    *portPinC &= ~0x01;

    // Configure ADC
    ADMUX |= 0x40; // Reference voltage on AVCC
    ADMUX |= 0x20; // Left adjust result (8-bit resolution)
    ADCSRA |= 0x80; // Enable ADC
}

uint8_t read_ADC() {
    // Start conversion
    ADCSRA |= 0x40;

    // Wait for conversion to complete
    while (ADCSRA & 0x40);

    // Return ADC value
    return ADCH;
}

int main() {
    // Initialize PWM and ADC
    init_PWM();
    init_ADC();

    // Initialize serial communication
    Serial.begin(9600);

    // Set duty cycle based on the last two digits of My student ID
    uint8_t duty_cycle = 24;

    // Calculate timer value for the desired duty cycle and period
    uint8_t timer_value = (duty_cycle * 255) / 100;

    // Set the initial duty cycle
    OCR0A = timer_value;

    // Main loop
    while (1) {
        // Extract ADC values for at least 5 seconds
        for (int i = 0; i < 5; i++) {
            uint8_t adc_value = read_ADC();

            // Print ADC value to serial
            Serial.println(adc_value);

            // Delay for a short interval
            MyDelay(1000);
        }

        // Toggle the duty cycle for the next iteration
        OCR0A = 255 - timer_value;
    }

    return 0;
}

void MyDelay(unsigned long mSec)
{
volatile unsigned long i;
unsigned long endT = 500 * mSec;
for (i = 0; i < endT; i++);
}