//STAGE 1
//*** DEFINE PINS HERE
const int LDR_pin = A0;
const int Relay_pin = 11;
const int LED_pin = 2;

//*** DEFINE VARIABLES HERE
int LDR_current = 0;
int LDR_previous = 0;
int Motor_command = 0;
unsigned long Start_t = 0;
unsigned long Current_t = 0;
int Slot_counter = 0;
float RPM = 0;
int for_counter = 0;

//*** DEFINE EXP PARAMETERS HERE
int LDR_background = 1023;
int LDR_step = 200;
int LDR_threshold = LDR_background + LDR_step;

//number of slots in zoetrope
int no_slots = 12;

//define variable for motor demand (0-255), 8-bit PWM. Start on at 50% demand.
int motorDemand = 127;

/* 
--------------------------------------------  
-------- End Initialise Variables ----------
--------------------------------------------
*/

/* 
----------------------------------  
-------- Begin Setup Loop --------
----------------------------------
*/

void setup() {

  // initialize serial communication at 115200 bits per second.
  Serial.begin(9600);
  //**** STAGE 2a **** 
  pinMode(LDR_pin, INPUT);
  pinMode(Relay_pin, OUTPUT);
  pinMode(LED_pin, OUTPUT);

  //**** STAGE 2b **** 
  digitalWrite(LED_pin, HIGH);
  Motor_command = 255 / 2;
  analogWrite(Relay_pin, Motor_command);

  //**** STAGE 2c *****   Find the background LDR value here
  find_LDR_background(); //you must write this function - see bottom of code!

}

/* 
-------------------------------
------- End Setup Loop --------
-------------------------------
*/

/* 
----------------------------------  
-------- Begin Main Loop ---------
----------------------------------
*/

void loop() {

  // **** STAGE 3 ****

  Slot_counter = 0;

  Start_t = micros();

  // **** STAGE 3b **** MEASURE THE RPM OF THE ZOETROPE

  do {

    LDR_previous = LDR_current;
    LDR_current = analogRead(LDR_pin);

    //if light threshold is crossed, increment cross count
    if (LDR_current > LDR_threshold && LDR_previous < LDR_threshold) {
      Slot_counter = Slot_counter++;
    }
    //update previous LDRval
    LDR_previous = LDR_current;
  }
  while (Slot_counter < no_slots);

  // **** STAGE 4 **** 
  //Find the end time of the rotation
  Current_t = micros();
  //Find the elapsed time for 1 rotation
  RPM = (Current_t - Start_t) / (1000 * 60);
  //
  Serial.println(RPM);
  //  **** STAGE 5 **** Automate the control?!

  // delay before starting again...
  delay(1000);

}

/* 
----------------------------------  
--------- End Main Loop ----------
----------------------------------
*/

/* 
----------------------------------------------------------------------------- 
--------- Declare User Defined Functions to be called by Main Loop ----------
-----------------------------------------------------------------------------
*/

void printOutputs() {
  // DEFINE YOUR FUNCTION HERE TO PRINT OUTPUTS - OPTIONAL!
}

void find_LDR_background() {
  for (for_counter = 0; for_counter = 500; for_counter++) {

    LDR_previous = LDR_current;
    LDR_current = analogRead(LDR_pin);

    if (LDR_background > LDR_current); {
      LDR_background = LDR_current;
    }
  }
  LDR_threshold = LDR_background + LDR_step;
}

/* 
--------------------------------------------------------------------------------- 
--------- End Declare User Defined Functions to be called by Main Loop ----------
---------------------------------------------------------------------------------
*/