#4.4.7.1. 예제 

#define ECHO 3

#define TRIG 4

void setup() {

pinMode(ECHO, INPUT);

pinMode(TRIG, OUTPUT);

Serial.begin(9600);

}

void loop() {

digitalWrite(TRIG, LOW);

delayMicroseconds(2);

digitalWrite(TRIG, HIGH);

delayMicroseconds(10);

digitalWrite(TRIG, LOW);

long dist = (pulseIn(ECHO, HIGH)) / 58.2;

 Serial.println(dist);

if (dist < 10) {

tone(11, 362, 100);

delay(100);

} else if (dist < 20) {

tone(11, 362, 100);

delay(250);

} else if (dist < 30) {

tone(11, 362, 100);

delay(500);

} else {

noTone(11);

}

 }

}