const int pingPin = 19; //D19
int inPin = 18; //D18
int D13 = 13;
#include <LiquidCrystal_I2C.h>

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
}

void loop() {
  // put your main code here, to run repeatedly:
  long duration, cm;

  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);

  digitalWrite(pingPin, LOW);
  pinMode(inPin, INPUT);
  duration = pulseIn(inPin, HIGH);

  cm = microsecondsToCentimeters(duration);

  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  if (cm <= 15){
    pinMode(D13, OUTPUT);
    digitalWrite(D13, HIGH);
  } else {
    digitalWrite(D13, LOW);
  }


  delay(500);
}
long microsecondsToCentimeters(long microseconds)
{
return microseconds / 29 / 2;
}