int trigger = 9 ;
int echo = 8 ;
long duration ;
float distance ;


void setup() {
  
  // Open serial communications and wait for port to open:
  
  Serial.begin(9600);
  
     // wait for serial port to connect. Needed for native USB port only
    
    pinMode(trigger,OUTPUT); 
    pinMode(echo,INPUT); 
}

void loop() { // run over and over
      digitalWrite(trigger,LOW); 
      
      delayMicroseconds(2);
      
      digitalWrite(trigger, HIGH);
      
      delayMicroseconds(10);
      
      digitalWrite(trigger, LOW); 
      
      duration = pulseIn(echo, HIGH);
      
      distance= duration * 0.034/2;
      
      Serial.println(distance);
      
      delay(10);               
}