#include <Arduino.h>

#define TRIG_PIN 12
#define ECHO_PIN 18

long duration;
float distance;

void setup() {
  Serial.begin(115200);
  delay(1000);

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

  Serial.println("HC-SR04 SERIAL OK");
}

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

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

  duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration == 0) {
    Serial.println("Out of range");
  } else {
    distance = (duration * 0.0343) / 2;
    Serial.print("Distance = ");
    Serial.print(distance);
    Serial.println(" cm");
  }

  delay(1000);
}