---

const int trigPin = 9;
const int echoPin = 10;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  unsigned long t = pulseIn(echoPin, HIGH, 25000);
  if (t == 0) Serial.println("Нет эха");
  else Serial.println(t * 0.0343 / 2.0);
  delay(150);
}