#define PIN_RPM 9
#define PIN_PWM 10

volatile unsigned int pulseCount = 0;
const unsigned int pulsesPerRevolution = 2;

unsigned long previousMillis = 0;
unsigned int rpm = 0;

void rpmISR() {
  pulseCount++;
}

int getSpeedForTemperature(){
  static int i = 0;
  switch(i++ % 5){
    case 0: return 100;
    case 1: return 140;
    case 2: return 180;
    case 3: return 220;
    case 4: return 255;
  }
  return 255;
}

void setup() {
  Serial.begin(115200);
  
  pinMode(PIN_RPM, INPUT_PULLUP);
  pinMode(PIN_PWM, OUTPUT);

  attachInterrupt(digitalPinToInterrupt(PIN_RPM), rpmISR, FALLING);
  digitalWrite(PIN_PWM, HIGH);
}

void loop() {
  uint8_t speed = getSpeedForTemperature();
  unsigned long currentMillis = millis();
  if(currentMillis - previousMillis >= 1000){
    noInterrupts();
    unsigned int count = pulseCount;
    pulseCount = 0;
    interrupts();

    rpm = (count * 60) / pulsesPerRevolution;

    Serial.println("Current Voltage: " + String(speed));
    Serial.println("Current RPM: " + String(rpm));
    Serial.println();

    previousMillis = currentMillis;
  }
  
  analogWrite(PIN_PWM, speed);
  
  delay(1000);
}