// Author: Ari Vuokila
// Modified by Kati Pitkänen on April 30, 2018
// Week 12 - Input Devices 
#include <math.h>

int tempPin = A0;                                 // Selects the input pin for the temperature sensor // INPUT
int Temperature;                                  // Initialization of the variable ‘Temperature’
float sensorValue;                                // Define the variable to store the sensor value data

void setup() {                                    // Start this function will after setup finishes and then repeat.

  Serial.begin(9600);
  pinMode(tempPin, INPUT);                        // Temperature sensor is in input pin PC0
}

void loop() {                                     // Run over and over again
  //Arduino converts an analog voltage input (0 - 5V) on tempPin to digital value (0 - 1023) = changes the values from 0-5 to a range 0-1023 that corresponds to the voltage the pin is reading 
  sensorValue = analogRead(tempPin);              // Read and store the analog input value coming from the temp sensor pin

  double Temp, T;                                 // Define the variables to show the temperature data
  double R = 10000 / (1023.0 / sensorValue - 1);  // Steinhart - Hart    /// Resistance = 10 k ohm     /// (2^10 = 1024)
  double L = 10000 / R;                           // L = R0/R // 10000/R = ReferenceResistance/ NominalResistance = ResistanceInNominalTemperature25oC)
  
  //T = 1.0/((1.0/(25.0 + 273.15)) + (log(R0/R))/3750))
  //T = 1.0/((1.0/(25.0 + 273.15)) + (log(L))/3750) * log(L))
  T = (0.0033540164 + 0.00026666666 * log(L));    // Steinhart-Hart 1/T=1/T0 + 1/B*ln(R0/R)
  T = 1/T;

  Temp = T - 273.15;                              // To get Celcius degrees Temperature = T - 273.15 (Kelvin degrees) 

  Serial.print("Temperature ");                   // To print information to the Serial Monitor 
  Serial.print(Temp);
  Serial.println(" C ");

  delay(500);
}