const int trig = A0,       echo = A1;
int time, distance;  double speed = 0.0343;

void setup() {
  pinMode(echo, INPUT);
  pinMode(trig, OUTPUT);
  for(int x = 4; x <= 9; x++){pinMode(x, OUTPUT);}
  Serial.begin(9600);
}
void loop() {
  distance = cal_distance(); Serial.println(distance);
  int ON  = map(distance, 2, 400, 9, 4);
  for(int x = 9; x >= ON; x--){digitalWrite(x, HIGH);}
  for(int x = 4; x < ON; x++) {digitalWrite(x, LOW);}
}

int cal_distance(){
  digitalWrite(trig, LOW);  delayMicroseconds(2);
  digitalWrite(trig, HIGH); delayMicroseconds(10);
  digitalWrite(trig, LOW);
  time = pulseIn(echo, HIGH);
  distance = (time * speed)/2;
  distance = constrain(distance, 2, 400);
  return distance;
}