// Ultrasonic Sensor and LED Interface with NodeMCU (ESP8266)
// If distance < 10 cm, turn on the LED; otherwise, turn it off

const int trigPin = T1; // TRIG pin of HC-SR04
const int echoPin = T2; // ECHO pin of HC-SR04
const int ledPin = T3;  // LED pin

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(115200);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH);
  float distance_cm = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");

  // Check if distance is less than 10 cm
  if (distance_cm < 10) {
    digitalWrite(ledPin, HIGH); // Turn on the LED
  } else {
    digitalWrite(ledPin, LOW);  // Turn off the LED
  }

  delay(500); // Wait for a moment before the next measurement
}