#include <Arduino.h>

#define TRIG_PIN 14
#define ECHO_PIN 27

#define LED_PIN 26



float readDistanceCm() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000); // timeout 30ms ≈ 5m
  if (duration == 0) return -1; // ถ้าไม่มี echo
  return (duration * 0.0343) / 2.0;
}

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

  Serial.println("ESP32 Rhythmic Distance Finder Started!");
}

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

  if (distance < 0) {
    Serial.println("No echo (out of range)");
    digitalWrite(LED_PIN, HIGH);
    delay(800);
    digitalWrite(LED_PIN, LOW);
    delay(800);
    return;
  }

  Serial.print("Distance: ");
  Serial.print(distance, 1);
  Serial.println(" cm");


  if (distance < 2) distance = 2;
  if (distance > 100) distance = 100;

 
  int delayMs = (int)((distance - 2) * (780.0 / 98.0) + 20);


  digitalWrite(LED_PIN, HIGH);
  delay(delayMs);
  digitalWrite(LED_PIN, LOW);
  delay(delayMs);
}