#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const int SDA_PIN  = 8;
const int SCL_PIN  = 9;
const int TRIG_PIN = 4;
const int ECHO_PIN = 5;

LiquidCrystal_I2C lcd(0x27, 16, 2);

float readDistanceCm() {
  // Trigger the ultrasonic burst
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo pulse width
  unsigned long duration = pulseIn(ECHO_PIN, HIGH, 30000); // 30 ms timeout

  if (duration == 0) {
    return -1.0; // no echo
  }

  return duration / 58.0; // cm
}

void setup() {
  Serial.begin(115200);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  Wire.begin(SDA_PIN, SCL_PIN);

  lcd.init();
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print("ESP32-S3 Ready");
  lcd.setCursor(0, 1);
  lcd.print("Ultrasonic LCD");
  delay(1500);
  lcd.clear();
}

void loop() {
  float distance = readDistanceCm();

  Serial.print("Distance: ");
  if (distance < 0) {
    Serial.println("Out of range");
  } else {
    Serial.print(distance, 1);
    Serial.println(" cm");
  }

  lcd.setCursor(0, 0);
  lcd.print("Distance:");

  lcd.setCursor(0, 1);
  lcd.print("                "); // clear line
  lcd.setCursor(0, 1);

  if (distance < 0) {
    lcd.print("Out of range");
  } else {
    lcd.print(distance, 1);
    lcd.print(" cm");
  }

  delay(300);
}