/*
   Forum: https://forum.arduino.cc/t/stepper-motor-runs-continuously/1183191
   Wokwi: https://wokwi.com/projects/379848824166403073
*/

#include <Stepper.h>

/*
  The Wokwi Simulation uses a stepper motor with 200 steps/revolution @ 100 rpm
   Comment the line "#define SIMULATION" out to use 2048 steps/revolution @ 9 rpm instead

*/
#define SIMULATION


#ifdef SIMULATION
constexpr int StepsPerRevolution = 200;
constexpr int motSpeed = 100;  // rpm
#else
constexpr int StepsPerRevolution = 2048;
constexpr int motSpeed = 9;
#endif

// The sensor value must be below rotateThreshold to start rotation
constexpr int rotateThreshold = 400;
// The sensor must provide a value above the resumeThreshold
// before the next rotation may start (Hysteresis to avoid switching between
// both situations close around the value of rotateThreshold)
constexpr int resumeThreshold = 450;


constexpr byte lightPen = A0;
constexpr unsigned long measurementInterval = 500L;

// Define the no of rotations after rotation is triggered
constexpr unsigned long noOfRotations = 2L;

Stepper myStepper(StepsPerRevolution, 9, 11, 10, 12);

// Store the time in millis() when the measurement was done
// and use it to measure every measurementInterval [msec] only
unsigned long lastMeasurement = 0;
int lightVal;

// The variable triggerRotationAllowed is set to false in the beginning 
// so that the motor will NOT rotate when the sketch starts with the 
// light value below rotateThreshold! The light value has to exceed
// resumeThreshold once to allow to trigger rotations.
boolean triggerRotationAllowed = false;
// Holds the no of steps that the motor shall move
unsigned long noOfSteps = 0;

void setup() {
  Serial.begin(9600);
  myStepper.setSpeed (motSpeed);
}

void loop() {
  checkLightSensor();
  rotateIfRequired();
}


void checkLightSensor() {
  // Does a measurement every measurementInterval [msec]
  if (millis() - lastMeasurement >= measurementInterval) {
    lastMeasurement = millis();
    lightVal = analogRead(lightPen);
    Serial.println(lightVal);
    // If value below the threshold AND rotation is allowed)
    if (lightVal < rotateThreshold && triggerRotationAllowed) {
      // then set noOfSteps to the steps required von noOfRotation revolutions
      noOfSteps = noOfRotations * StepsPerRevolution;
      // Store that the rotation is triggered now
      // to avoid running into this part of the code
      // while lightVal stays below resumeThreshold
      triggerRotationAllowed = false;
    }
    // In case that lightVal is above resumeThreshold
    // and any earlier rotations are done (noOfSteps == 0)
    // allow
    if (lightVal > resumeThreshold && noOfSteps == 0) {
      triggerRotationAllowed = true;
    }
  }
}

void rotateIfRequired() {
  // If noOfSteps is greater than zero make one step
  if (noOfSteps > 0 ) {
    // Do one step
    myStepper.step(1);
    // Reduce the number of steps by 1 to get the remaining steps
    noOfSteps--;
  }
}