// TTA Demo NTC Sensor
#include <LiquidCrystal.h> // Library for LCD
LiquidCrystal lcd (7,6,5,4,3,2); //5，4，3，2 for D4,D5,D6,D7 for string
unsigned long startTime;  // define a long variable to store "startTime"
bool timerStarted = false; // timer initial status
bool buttonPressed = false; 
const int buttonPin = 8;
const int ledPin = 13; //  Constant - define constant to store output pin 13 for the LED
const int buzzerPin = 12; // output pin 12 for the buzzer
const int sensorPin = A0;
float baselineTemp;

// variable foe NTC sensor only
const float BETA = 3950; // should match the Beta Coefficient of the thermistor

void setup() {
  Serial.begin(9600); // set booud rate to read time
  lcd. begin(16,2); // set screen size
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT); // set pin for LED output
  pinMode(buzzerPin, OUTPUT); // set pin for buzz output
}

void loop() {

  if (digitalRead(buttonPin) == HIGH && !buttonPressed) {
    buttonPressed = true;
    // LED flash
    for (int i = 0; i < 5; ++i) {
      digitalWrite(ledPin, HIGH);
      delay(500);
      digitalWrite(ledPin, LOW);
      delay(500);
    }
    // LED on
    digitalWrite(ledPin, HIGH);
    // buzz for 1 second
    tone(buzzerPin,2000,1000);
    // record baseline temperature
    delay(1000);
    int sensorVal_base=analogRead(sensorPin); // read voltage on sensor
    baselineTemp = 1 / (log(1 / (1023. / sensorVal_base - 1)) / BETA + 1.0 / 298.15) - 273.15;  
    Serial.println(baselineTemp);
    // start timer
    startTime = millis()/1000;
    timerStarted = true;  
  } else if (digitalRead(buttonPin) == LOW) {
    buttonPressed = false;
  }

  // if timer starts, the program starts
  if (timerStarted) {
    unsigned long elapsedTime = millis()/1000 - startTime;

  int sensorVal=analogRead(sensorPin); // read voltage on sensor
  // write time in LCD and in Serial
  unsigned int minutes = elapsedTime / 60; //convert into minutes
  unsigned int seconds = elapsedTime % 60; //convert into seconds

  lcd.setCursor(0,0);  //set location on screen
  lcd.print("Time:");  //print "Time" to LCD
  lcd.print(" ");  
  lcd.print(minutes);
  lcd.print(" m ");
  lcd.print(seconds);
  lcd.print(" s");
  lcd.setCursor(0,1); // change line
  lcd.print("Temp: ");
  
  //convert the return value for LM35 sensor
  //float voltage=(sensorVal*5.00)/1024;
  //float temperature=voltage*100;   
  //lcd.print(temperature); // print current temperature to LCD

  // convert the return value for NTC sensor
  float celsius = 1 / (log(1 / (1023. / sensorVal - 1)) / BETA + 1.0 / 298.15) - 273.15;  
  lcd.print(celsius); // print current temperature to LCD

  // print information on Arduino IDE since program started
  Serial.print("Time: ");
  Serial.print(elapsedTime);
  Serial.print("sec, Sensor Value: ");
  Serial.print(sensorVal);
  //Serial.print(", Volts: ");
  //Serial.print(voltage);
  Serial.print(", degrees C: ");
  //Serial.println(temperature);
  Serial.println(celsius);
  delay(500);  
  
  if(celsius <= baselineTemp - 2.00){
    timerStarted = false;
    tone(buzzerPin,2000,1000);
    delay(1000);
    }  
  }

}