#define TRIG_PIN D3
#define ECHO_PIN D2
#define LED_PIN D5     

long duration;
int distance;
int ledBrightness;

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

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

  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

  duration = pulseIn(ECHO_PIN, HIGH, 30000);

  distance = duration * 0.0343 / 2;

  if (distance >= 30 || distance == 0) {
    ledBrightness = 0;
  } 
  else if (distance <= 2) {
    ledBrightness = 255;
  } 
  else {
    ledBrightness = map(distance, 30, 2, 0, 255);
  }
  analogWrite(LED_PIN, ledBrightness);
  delay(50);
}