#define trig 2
#define echo 3
#define buzzer 4
void setup() {
  pinMode(trig, OUTPUT) ;
  pinMode(echo, INPUT);
  pinMode(buzzer, OUTPUT);
  for (int i = 4 ; i <= 13 ; i++) {
    pinMode(i, OUTPUT) ;
  }
  Serial.begin(9600) ;
}
void loop() {
  digitalWrite(4, HIGH);
  digitalWrite(trig, LOW);
  digitalWrite(trig, HIGH);
  delayMicroseconds(5);
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  int t = (pulseIn(echo, HIGH)) / 2  ;
  int distance = t * 0.0343 ;
  int counter = map(distance, 0, 400, 4, 13) ;
  Serial.println(counter) ;
  for (int i = 4 ; i <= 13 ; i++ ) {
    if (i <= counter) {
      digitalWrite(i, HIGH);
    }
    else {
      digitalWrite(i, LOW) ;
    }
  }

  // 0 -> 400   => 0 -> 10
  delay(30) ;

}