//need to define digitalRead() enabled pin for square wave length reading from the photo-interrupter
//need to define pin for gate input to the transistor that enables the motor;
    //PWM pin drives the transistor base

#define PH_INTERRUPTER 33 //pin to enable the reading from the photo-interrupter
#define MOTOR_PIN 13


void setup() {
    //PWM pin that controls the speed of the motor via the transistor logic gate
    //digitalRead pin that reads the speed of the motor via square wave signal
    //length as a part of full cycle of light
    pinMode(MOTOR_PIN, OUTPUT);
    pinMode(PH_INTERRUPTER, INPUT);
    Serial.begin(9600);
    Serial.println("start");
}

void loop() {
//code for outputting sensor value
    //delay between each counting procedure cycle
    delay(1000);
    //the pulseIn function measures the time length of a signal of certain type - HIGH or LOW
    //and returns its length in ms, or 0 if no such was detected.
    float duration_on = pulseIn(PH_INTERRUPTER,HIGH);//signal caught
    float duration_off = pulseIn(PH_INTERRUPTER,LOW);//no light
    //speed of motor is calculated as the amount of full cycles of the same measured time
    //length (duration_on/_off) can be fitted within a minute of time (60000ms),
    //2 signals per physical spin

    long speed_of_Motor = (60000000)/((duration_on + duration_off) *2);
    Serial.println(speed_of_Motor);

//code for running the motor with PWM
    //setting the speed
       int speedset_rpm = 1550 //within a range between 0 and 3700 rpm to convert
       int converted_speedset_PWM = speedset_rpm/3700*255;
    //setting duty cycle for the PWM after conversion from speedset
       int motor_PWM_duty_cycle = 1; //value needs to be between 0 and 255
    //set by the user, calibrated
       analogWrite(MOTOR_PIN, motor_PWM_duty_cycle);
        //set tolerance
        int tolereance = 20;
    int max_speed_set = speedset + tolerance;
    int min_speed_set = speedset - tolerance;
         if (speed_of_Motor <= min_speed_set){
             //reset speed to the set by user
             digitalWrite(MOTOR_PIN,HIGH);
         }
         if (speed_of_Motor >= max_speed_set){
             //reset speed to the set by user
             digitalWrite(MOTOR_PIN,LOW);
         }
    delay(500);
}