#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4);
#define ECHO_PIN 2
#define TRIG_PIN 3

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(13, OUTPUT);
  lcd.init();
  lcd.backlight();
}


void loop() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  float distance = duration * 0.034 / 2;
  float y = (1E-06*distance*distance) + (1.0055*distance) + 0.0012;
  lcd.clear();
  lcd.setCursor(2, 0);
  lcd.print("Jarak: ");
  lcd.print(y);
  lcd.print(" cm");
  if(y < 200)
  {
    lcd.setCursor(0, 2);
    lcd.print("Hati Hati");
    digitalWrite(13, y);
    delay(50);
    digitalWrite(13, LOW);
    delay(100);
  }else{
    lcd.setCursor(0, 2);
    lcd.print("Jarak Aman");
  }
  delay(100);
}