#define TRIG 9
#define ECHO 8

void setup() {
  Serial.begin(9600);
  Serial.println("Ultrasonic Sensor");
}

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

  long dt = pulseIn(ECHO, HIGH);
  Serial.print("dt: ");
  Serial.println(dt);

  // v = dist * time
  // dist = v / time
  float distance = dt / 58.0;
  Serial.print("dist: ");
  Serial.println(distance);

  delay(1000);
}