#define trig 18
#define echo 5
void setup() {

  Serial.begin(115200);

  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);

}

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

  float time = pulseIn(echo ,HIGH);
  Serial.println("time =");
  Serial.println(time);
   float cm = 0.017 * time;
   Serial.println( "cm = ");
   Serial.println(cm);
}