#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);

const int TrigPin = 4;// # define trigpin 4
const int Echopin = 2;//# define echopin 2
long duration;
int distance;
#define rled 16
#define gled 17
#define buz  18

 void setup()
{
  Serial.begin(9600);
   Serial.begin(9600);
  lcd.init();          
  lcd.backlight();  

  lcd.setCursor(0,0);
  lcd.print("us__distance__!");
  delay(2000);
  lcd.clear();
  
  pinMode(TrigPin, OUTPUT );
  pinMode(Echopin, INPUT);
  pinMode(rled, OUTPUT );
  pinMode(gled, OUTPUT );
  pinMode(buz, OUTPUT);

}

 void loop()
 {

  digitalWrite(TrigPin , LOW);
  delayMicroseconds(2);
  digitalWrite(TrigPin , HIGH);
  delayMicroseconds(100);
  digitalWrite(TrigPin , LOW);


 duration = pulseIn(Echopin,HIGH);
 distance = duration*0.034/2;
 Serial.print("dist:");
 Serial.print(distance);
 Serial.println(" cm");

  lcd.setCursor(0,0);
  lcd.print("DIST : ");
  lcd.setCursor(4,0);
  lcd.println( distance);


 if (distance<100 )  
 {
  digitalWrite(rled, HIGH);
  digitalWrite(buz, HIGH);
  tone(buz,1000);
  delay(500);
  digitalWrite(gled, LOW);
  lcd.setCursor(0,1);
  lcd.print("__DANGER__!");
  

 }
 else
 {
  digitalWrite(rled, LOW);
  digitalWrite(buz, LOW);
  digitalWrite(gled, HIGH);
  lcd.setCursor(0,1);
  lcd.print("__ SAFE__ !"); 
}

  
 }