#include <LiquidCrystal.h>
#include <Servo.h>

#define pingPin 28
#define echoPin 27

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);
Servo daServo;

void setup() {
  pinMode(pingPin, OUTPUT);
  pinMode(echoPin, INPUT);
  daServo.attach(4);
  lcd.begin(16, 2);
}

void loop() {
  long duration, cm; // Allocate vars
  
  // send 10 us Pulse to Trig
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(pingPin, LOW);

  // We get the distance with the echo time
  duration = pulseIn(echoPin, HIGH);
  cm = microsecondsToCentimeters(duration);

  bool check = cm <= 100;
  daServo.write(90 * check + 90); // Check to lock door

  if (check) {
  lcd.setCursor(0, 0);
  lcd.print("Oh Hi!");
  } else {
    lcd.setCursor(0, 0);
    lcd.print("No one");
  }

  delay(1); // Adding a delay() here speeds up the simulation
}

// Distance Formula
long microsecondsToCentimeters(long microseconds) {
   return microseconds / 29 / 2;
}