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

#define trig 10  
#define echo 9 
#define servo 21  
#define rs 12 
#define en 11 
#define d4 5  
#define d5 4  
#define d6 3  
#define d7 2  
Servo myServo;
LiquidCrystal lcd(rs,en,d4,d5,d6,d7);
int a=0;
int dist=0;
void setup() {
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  myServo.attach(servo);
  myServo.write(0);
  lcd.begin(16, 2);
  dist = EEPROM.read(a);
  if (dist>400||dist <0) { 
    dist = 30; 
  }
  Serial.print("Current threshold:");
  Serial.println(dist);
}

void loop() {
  digitalWrite(trig, LOW);
  delay(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  long time = pulseIn(echo, HIGH);
  int distance = time * 0.034 / 2;
  lcd.setCursor(0, 1);
  lcd.print("Dist: ");
  lcd.print(distance);
  lcd.print("cm");
  if (distance>0&&distance<dist) {
    myServo.write(180);
    lcd.setCursor(0, 0);
    lcd.print("Door: Open              ");
  } else {
    myServo.write(0);
    lcd.setCursor(0, 0);
    lcd.print("Door: Closed            ");
  }
  if (Serial.available() > 0) {
    int newdist = Serial.parseInt();
    if (newdist!=0) {
      dist = newdist;
      EEPROM.write(a,newdist);
      Serial.print("Threshold set to: ");
      Serial.print(newdist);
      Serial.println(" cm");
      lcd.setCursor(0, 1);
      a=a+1;
  }
  delay(50);
  }
}