//includes  all necessary library
#include "DHT.h"
#include<Wire.h>
#include<LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

//Defines all pins
#define DHTPIN 8
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

//Defines all variables
int trig = 9;
int echo = 10;

long duration;
int distance;
float T;
float RH;
float velocity;


void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);

  lcd.init();
  lcd.backlight();

  dht.begin();

  Serial.begin(9600);//starts the serial communication

}
void loop() {

  ultrasonic();
  lcd_print();
  dht_speed();
}

//Read the temperatur and Humidity from DHT22 sensor
//and calculate the velocity(c = 331.4 + (0.6 x T) + (0.0124 x RH)) of sound
void dht_speed() {
  RH = dht.readHumidity();
  T = dht.readTemperature();
  velocity  = 331.4 + (0.6*T) + (0.0124 * RH);
  delay(1000);
}

//Calculate the distance from ultrasonic sensor
void ultrasonic() {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);

  digitalWrite(trig, HIGH);
  delayMicroseconds(10);

  digitalWrite(trig, LOW);

  duration = pulseIn(echo, HIGH);

  distance = (velocity*0.0001 * duration) / 2;
}
//Print velocity of sound and distance on the LCD display
void lcd_print() {

  lcd.setCursor(0, 0); //sets the location at which subsequent text write
  lcd.print("Velocity:");
  lcd.print(velocity);
  lcd.print("m/s");

  lcd.setCursor(0, 1);
  lcd.print("Distance: ");
  lcd.print(distance);
  lcd.print("CM");
}