#include <SoftwareSerial.h> 
#define RX 0
#define TX 1 

SoftwareSerial serial(RX, TX); 

#define echoPin 17 
#define trigPin 16 

// defines variables
long duration; 
int distance; 

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
  serial.begin(9600); 
  serial.println("Ultrasonic Sensor HC-SR04 Test"); // print some text in Serial Monitor
}
void loop() {
  // Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delay(1000);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delay(1000);
  digitalWrite(trigPin, LOW);
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  // Calculating the distance
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
  // Displays the distance on the Serial Monitor
  serial.print("Distance: ");
  serial.print(distance);
  serial.println(" cm");
}