/* 
--------------------------------------------  
-------- Begin Initialise Variables --------
--------------------------------------------
*/

//STAGE #1
//define pins
//add code here
const int transistor_pin = 2;
const int hall_pin = A0;

//define pendulum length
float length = 0.23;
const int ping_time = 200;
const int threshold_value = 530;

//Sensor readings
int hall_voltage = 0;

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


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

void setup() 
{

  // initialize serial communication at 115200 bits per second.
  Serial.begin(9600);

  //STAGE 2 - pin modes
  pinMode(transistor_pin,OUTPUT);
  pinMode(hall_pin, INPUT);

  
  //Control solenoid
  digitalWrite(transistor_pin,LOW);
  digitalWrite(transistor_pin, HIGH);
  delay(ping_time); //wait for 200ms
  digitalWrite(transistor_pin,LOW);
}

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

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

  //STAGE 3 - the main loop
void loop() 
{
  // variables for timing
  unsigned long starttime = 0;
  unsigned long currenttime = 0;
  unsigned long elapsedtime = 0;
  int hall_voltage_old = 0;
  int peak_count = 0;
  float gravity;
  float T_period;
  

  //get start time
  starttime = millis();


  do  {
    
     //read Hall effects sensor
     hall_voltage = analogRead(hall_pin);
     
     //get current time
     currenttime = millis();

     //calc elapsed time in milliseconds
     elapsedtime = currenttime - starttime;


	   if(hall_voltage >= threshold_value && hall_voltage_old < threshold_value) {
     peak_count = peak_count + 1; // register that peak has occured
    

     }

     hall_voltage_old = hall_voltage; // setting current reading to the old one


	 //Print data back to the computer
	   Serial.print (elapsedtime);
     Serial.print (",");
     Serial.println (hall_voltage);
     Serial.print (",");
     Serial.println(peak_count);
     delay(1);
     
	
  } while (peak_count < 10);

  
  //STAGE 5 - calculate Gravity...
  T_period = (elapsedtime*0.001) / 5;

  //evaluate gravity
  gravity = length / (sq(T_period / (2*(PI))));
  

  //STAGE 5b - print your answer...
  Serial.print("gravity = ");
  Serial.print(gravity);
  Serial.print('\n');
  //Serial.println("T_period = ");
  //Serial.print(T_period);

  delay(10000); //wait for 10 seconds - LEAVE THIS FOR RELOAD TO WORK PROPERLY!
}

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