---

#define TRIG_PIN 3
#define ECHO_PIN 2
#define LED 5

void setup()
{
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  long duration;
  float sm;

  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

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

  duration = pulseIn(ECHO_PIN, HIGH);

  sm = duration / 58.0;

  Serial.print("Расстояние = ");
  Serial.print(sm);
  Serial.println(" см");

  if (sm < 2)
    digitalWrite(LED, HIGH);
  else
    digitalWrite(LED, LOW);

  delay(100);
}