const int trig = 17;
const int echo = 16;
const int ledpin=13;
float distance;
float duration;

void setup() 
{
  Serial.begin(115200);   
  pinMode(echo, INPUT);       
  pinMode(trig, OUTPUT);      
}

void loop() 
{
  distance = getdistance();   
  Serial.print("Distance = "); 
  Serial.print(distance);     
  Serial.println(" cm");    
  delay(2000);               
}

float getdistance()
{
  digitalWrite(trig, LOW);    
  digitalWrite(trig, HIGH);   
  delayMicroseconds(10);   
  digitalWrite(trig, LOW);    
  duration = pulseIn(echo, HIGH); 
  return (duration * 0.0344) / 2; 
}