#include <Servo.h>

#define PIN_TRIG 3
#define PIN_ECHO 2
#define SERVO_PIN 11

Servo servo;

const int open = 90;
const int close = 0;
const int threshold = 75;
long lastUpdate = 0;
const int updateInterval = 200;

//function that returns distance in inches
int distance(){
  digitalWrite(PIN_TRIG,HIGH);
  delayMicroseconds(10);
  digitalWrite(PIN_TRIG,LOW);

  int duration = pulseIn(PIN_ECHO,HIGH);
  //printing distance in inches
  int distance = duration/148;
  Serial.print("Distance in inches: ");
  Serial.println(distance);
  return distance;
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(PIN_TRIG,OUTPUT);
  pinMode(PIN_ECHO,INPUT);
  servo.attach(SERVO_PIN);
  servo.write(close);
}

void loop() {
  // put your main code here, to run repeatedly:
  if(millis()-lastUpdate >= updateInterval){
    lastUpdate = millis();
    int dis = distance();
    if(dis<=75){
      servo.write(open);
    }else{
      servo.write(close);
    }
  }
}