아놀로그 핀 디지털 핀으로 대체 가능함

//----------------------------------------
const int ultra1_trig_PLUS_pin = 13;
const int ultra1_echo_PLUS_pin = 12;
const int ultra2_trig_SUB_pin = A0;
const int ultra2_echo_SUB_pin = A1;
int number = 0;
//----------------------------------------
void setup() {
  // put your setup code here, to run once:
  // $  ultra1_ $
  pinMode(ultra1_trig_PLUS_pin,  OUTPUT);  // pinNumber: 13
  pinMode(ultra1_echo_PLUS_pin,   INPUT); // pinNumber:  12

  // $ ultra2_ $
  pinMode(ultra2_trig_SUB_pin, OUTPUT); // pinNumber: A0
  pinMode(ultra2_echo_SUB_pin,   INPUT); // pinNumber: A1

  //
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  // $  ULTRA1 ----------------------------------------------------------------
  digitalWrite(ultra1_trig_PLUS_pin, LOW);
  delayMicroseconds(2);
  digitalWrite(ultra1_trig_PLUS_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(ultra1_trig_PLUS_pin, LOW);
  long distance_plus = pulseIn(ultra1_echo_PLUS_pin, HIGH)/58.2;
 
  //$ ULTRA2  ----------------------------------------------------------------
  digitalWrite(ultra2_trig_SUB_pin, LOW);
  delayMicroseconds(2);
  digitalWrite(ultra2_trig_SUB_pin, HIGH);
  delayMicroseconds(10);
  digitalWrite(ultra2_trig_SUB_pin, LOW);
  long distance_sub = pulseIn(ultra2_echo_SUB_pin, HIGH)/58.2;

 
  if (distance_plus < 10) {
    Serial.print("distance_plus -> ");
    Serial.print(distance_plus);
    Serial.println(" cm");
    number++;
    Serial.print("number is ");
    Serial.println(number);
  }  else  {  //distance_plus >= 10
    if (distance_sub < 10) {
      Serial.print("distance_sub -> ");
      Serial.print(distance_sub);
      Serial.println(" cm");
      number--;
      Serial.print("number is ");
      Serial.println(number);
    }
  }
}