#define LED_PIN D0
#define TRIG D1
#define ECHO D2


void setup() {
  Serial.begin(115200);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(LED_PIN, OUTPUT);
  Serial.println("READY");
}

void loop() {
  if (Serial.available()) {
    String command = Serial.readStringUntil('\n');
    command.trim();

    if (command == "ON") {
      digitalWrite(LED_PIN, HIGH);
      Serial.println("LED ON");
    } else if (command == "OFF") {
      digitalWrite(LED_PIN, LOW);
      Serial.println("LED OFF");
    } else if (command == "SCAN") {
      digitalWrite(TRIG, LOW);
      delayMicroseconds(2);
      digitalWrite(TRIG, HIGH);
      delayMicroseconds(10);
      digitalWrite(TRIG, LOW);

      long duration = pulseIn(ECHO, HIGH);
      int distance = duration * 0.0343 / 2;

      Serial.print("DISTANCE:");
      Serial.println(distance);
    }
  }
}