#include <Servo.h>

Servo myServo;           // Create a Servo object
const int servoPin = 10; // D10 is OC1B on Pro Mini
const int ledPin = 13;
const int analogPin = A0;
const int SensorPin = 2;

volatile uint16_t pulses = 0,ppm = 0; //pulse per minute


// Interrupt Service Routine (ISR)
void INT0_ISR() {
  pulses++;
}

void setup_timer() {

  // Stop Timer2
  TCCR2A = 0;
  TCCR2B = 0;
  TCNT2 = 0;
  // Set compare match value for 100ms
  // Clock = 16 MHz, Prescaler = 1024
  // Tick = 16,000,000 / 1024 = 15,625 ticks/sec
  // 100ms = 0.1s → 0.1 * 15625 = 1562.5 ticks
  // Since Timer2 is 8-bit, we can't reach 1562 in one cycle.
  // So we will count multiple compare matches.
  OCR2A = 50; // Compare match every ~16ms (250 counts at 1024 prescaler)
  // CTC mode
  TCCR2A |= (1 << WGM21);
  // Prescaler = 1024
  TCCR2B |= (1 << CS22) | (1 << CS21) | (1 << CS20);
  // Enable compare match interrupt
  TIMSK2 |= (1 << OCIE2A);
  // Enable global interrupts
  sei();
}

void setup() {
  pinMode(ledPin, OUTPUT);       
  Serial.begin(115200);            // Initialize Serial
  myServo.attach(servoPin);      // Attach servo to pin 10
  
  attachInterrupt(digitalPinToInterrupt(SensorPin), INT0_ISR, FALLING);
  setup_timer();
}

void loop() {
  int analogValue = analogRead(analogPin); // Read from A0 (0–1023)
  int angle = map(analogValue, 0, 1023, 0, 180); // Map to 0–180 degrees
  Serial.print("pulses: ");
  Serial.println(pulses);

  myServo.write(angle);  // Set servo angle

  delay(1000);
}


ISR(TIMER2_COMPA_vect) {
  static uint16_t ticks = 0;
  static bool ledState = false;
  ticks++;
  if (ticks >= 150) { // 150 => 1s
    ticks = 0;
    ledState = !ledState;
    ppm = pulses;
    pulses = 0;
    digitalWrite(ledPin, ledState);
  }
}