#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C LCD = LiquidCrystal_I2C(0x27, 20, 4);

const float BETA = 3950;
int ledPin = 2; //LED
int motionIn = 12; //pir motion
int analogIn = 35; //NTC temperature sensor
int pirState = LOW; //pir state
int val = 0;
float sum = 0; //calculate total temperature
int count = 0; //record the number of temperature have been detected
int delayCount = 0; //record if the motion goes low for over 9 seconds
int ifStart = 0; //record if current state goes from high to low

void LCD_print(float celsius, int flag){
  LCD.setCursor(1, 0); //print current temperature
  LCD.print("current: ");
  LCD.println(celsius);
  LCD.setCursor(1, 1);
  if(celsius < 10){
    digitalWrite(ledPin, HIGH); //tem < 10, light the LED
    LCD.println("LED On");
  }
  else{
    digitalWrite(ledPin, LOW);
    LCD.println("      ");
  }
  if(flag == 1){
    LCD.setCursor(1, 2); //print average temperature
    LCD.print("average: ");
    LCD.println(sum / count);
  }
  else{
    LCD.setCursor(1, 2); //cover average temperature
    LCD.println("                 ");
  }
}

void setup() {
  pinMode(motionIn, INPUT); //set motion input
  pinMode(analogIn, INPUT); //set analog input
  pinMode(ledPin, OUTPUT); //set LED output
  analogReadResolution(10);
  LCD.init();
  Serial.begin(9600);
}

void loop() {
  int analogValue = analogRead(analogIn); //read temperature
  float celsius = 1 / (log(1 / (1023. / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
  val = digitalRead(motionIn); //detect motion
  if(val == HIGH){
    if(pirState == LOW){
      Serial.println("Motion detected!");
      pirState = HIGH;
    }
    ifStart = 1;
    sum += celsius; //calculate the sum of current temperature
    count++; //record the number of temperature
    LCD_print(celsius, 1);
  }
  else{
    if(pirState == HIGH){
      Serial.println("Motion ended!");
      pirState = LOW;
    }
    if(ifStart == 1) LCD_print(celsius, 0);
    if(delayCount == 3){
      digitalWrite(ledPin, LOW);
      LCD.clear();
    }
  }
  if(val == HIGH){
    delay(500); //high: delay 0.5 seconds
    delayCount = 0;
  }
  else{
    delay(3000); //low: delay 3 seconds
    delayCount++;
  }
}