#include <Arduino.h>
#include <BluetoothSerial.h>

#define TRIGGER_PIN 3
#define ECHO_PIN 4
#define LED 2
#define SPEED_SOUND 34300 //speed in cm/s

BluetoothSerial SerialBT;
int Threshold=0;

void setup() {
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  SerialBT.begin("Hello ESP32_BT");
  pinMode(TRIGGER_PIN,OUTPUT);
  pinMode(LED,OUTPUT);
  pinMode(ECHO_PIN,INPUT);
  digitalWrite(TRIGGER_PIN,LOW);
  digitalWrite(LED,LOW);
}

void loop() {
  SerialBT.print("Enter Threshold in cm: ");
  if (SerialBT.available()) {
    Threshold = SerialBT.parseInt(); // converting to int
  }
  Serial.print("Proximity Threshold set to: ");
  Serial.println(Threshold);
  digitalWrite(TRIGGER_PIN,HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN,LOW);
  long time=pulseIn(ECHO_PIN,HIGH);
  float ans=((time/1e6)*SPEED_SOUND)/2;
  // Serial.print("Distance Reading in cm: ");
  // Serial.println(ans);
  // SerialBT.print("Distance Reading in cm: ");
  // SerialBT.println(ans);
  if(ans<Threshold){
    SerialBT.println("Object in Proximity!");
    digitalWrite(LED,HIGH);
  } else{
    digitalWrite(LED,LOW);
  }
  delay(2000);
}