//STAGE #1
//Create variables for:
const int transistor_pin = 2 ; //The pin controlling the Solenoid (Table 1)
const int sensor_pin = A0 ; //The pin attached to the Hall-Effect Sensor (Table 1)]
int voltage = 0 ; //The voltage of the Hall Effect Sensor (as an int)
const float pendulength = 0.3 ; //The pendulum length (as a float ) 

void setup() 
{

  // initialize serial communication at 9600 bits per second.
  Serial.begin(9600);

  //STAGE 2 - pin modes
  pinMode(transistor_pin, OUTPUT);
  pinMode(sensor_pin, INPUT);
  
  //Control solenoid
  digitalWrite(transistor_pin, LOW);
  digitalWrite(transistor_pin, HIGH);
  delay(500);
  digitalWrite(transistor_pin, LOW );
 
 Serial.println("Initialisation complete");
}


  //STAGE 3 - the main loop
void loop() 
{

  //Array for gravity
  float gravities[9];

  //Variables for timing
  unsigned long startTime = 0;
  unsigned long currentTime = 0;
  unsigned long peakTime = 0;
  unsigned long half_T = 0;
 
 //Variable for previous voltage and peak time
  int prev_voltage = 0;
  unsigned long prev_peakTime = 0;

 //Variable for peak counter
  int num_peaks = 0;

  //get start time
  startTime = micros();

  //Progress check
  Serial.println("Variables assigned");
  Serial.print("Gravity array - ");

  progress_check(gravities);

  

  do  {
    
     //read Hall effects sensor
     voltage = analogRead(sensor_pin);

     //Identify if peak
     if (voltage>=550 && prev_voltage<550) {

      //Increment peak counter
      num_peaks = num_peaks + 1 ;

      //get current time
      currentTime = micros();

      //Calc time of peak in microseconds
      peakTime = currentTime - startTime ;
     
      //Calc half period and gravity (if applicable)
      if (num_peaks > 1) {
        half_T = peakTime-prev_peakTime;
        gravities[num_peaks-2] = gravity_calc(half_T);
      
        //Progress check
        progress_check(gravities);
      }
  Serial.println(); // Move to the next line after printing the array

      prev_peakTime = peakTime;
    }

      prev_voltage = voltage;
     //Add delay
     delayMicroseconds(50);
	
  } while (num_peaks < 10);

  
  //STAGE 5 - calculate Gravity...
  float gravity = average_calc(gravities);

  //STAGE 5b - print your answer
  Serial.print("gravity = ");
  Serial.print(gravity);
  Serial.print(" ms^-2");
  
  delay(10000); //wait for 10 seconds - LEAVE THIS FOR RELOAD TO WORK PROPERLY!
}

//Function finds gravity based on half period
float gravity_calc(unsigned long half_T) {
  float gravity = sq(PI)*pendulength / sq(half_T) ;
  return gravity;
}

//Function finds average of an array (length 9)
float average_calc(float gravities[]) {
  float sum = 0;
    for (int i = 0; i < 9; i++) {
        sum = sum + gravities[i];
    }
    return sum / 9;
}

//Function checks progress of experiment
void progress_check(float gravities[]) {
    // Print each element of the gravities array
  for (int i = 0; i < 9; i++) {
    Serial.print(gravities[i]);
    Serial.print(", ");
  }
  Serial.println(); // Move to the next line after printing the array
}