#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define TRIG_PIN 14 // ESP32 pin GPIO14 connected 
#define ECHO_PIN 27 // ESP32 pin GPIO27 connected
#define DISTANCE_THRESHOLD 50 //value in CM

float duration_us, distance_cm;

Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1); // create SSD1306 display object connected to I2C

String tempString;

void setup() {
 Serial.begin(115200);
 pinMode(TRIG_PIN, OUTPUT);
 pinMode(ECHO_PIN, INPUT);

 
 if(!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
Serial.println(F("SSD1306 allocation failed"));
 while (true);
 }
delay(2000); // wait for initializing
oled.clearDisplay(); // clear display
oled.setTextSize(2); // text size
oled.setTextColor(WHITE); // text color
oled.setCursor(0, 10); // position to display

tempString.reserve(10); // to avoid fragmenting memory when using String
}
void loop() {
 // generate 10-microsecond pulse to TRIG pin
 digitalWrite(TRIG_PIN, HIGH);
 delay (100);
 digitalWrite(TRIG_PIN, LOW);
 // measure duration of pulse from ECHO pin
  duration_us = pulseIn(ECHO_PIN, HIGH);// calculate the distance
  distance_cm = 0.017 * duration_us;// print the value to Serial Monitor
  
  if(distance_cm < DISTANCE_THRESHOLD)

 Serial.print("distance: ");
 Serial.print("distance_cm");
 Serial.println(" cm");
 tempString = String(distance_cm, 2); // two decimal places
 tempString += " cm";
 Serial.println(tempString); // print the temperature in Celsius to Serial Monitor
 oledDisplayCenter(tempString); // display temperature on OLED
}

void oledDisplayCenter(String text) {
 int16_t x1;
 int16_t y1;
 uint16_t width;
 uint16_t height;
 oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);
 // display on horizontal and vertical center
 oled.clearDisplay(); // clear display
 oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2);
 oled.println(text); // text to display
 oled.display();
}