#define trigger_pin 9
#define echo_pin 10
unsigned long duration = 0;
int distance = 0;

void setup() {
  // put your setup code here, to run once:
  pinMode(trigger_pin, OUTPUT);
  pinMode(echo_pin, INPUT);
  Serial.begin(115200);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(trigger_pin, LOW);
  digitalWrite(trigger_pin, HIGH);
  digitalWrite(trigger_pin, LOW);
  duration = pulseIn(echo_pin, HIGH);
  distance = duration * 0.034/2;
  Serial.print("distance : ");
  Serial.print(distance);
  Serial.println("cm");
  
}