#4.13.3.1. 예제 

int in3 = 2;

int in4 = 3;

int en2 = 5;

void setup() {

 pinMode(in3, OUTPUT);

 pinMode(in4, OUTPUT);

 pinMode(en2, OUTPUT);

}

void loop() {

    digitalWrite(in3, HIGH);

    digitalWrite(in4, LOW);

    analogWrite(en2, 150);

    delay(2000);

    analogWrite(en2, 255);

    delay(2000);

    digitalWrite(in3, LOW);

    digitalWrite(in4, HIGH);

    analogWrite(en2, 150);

    delay(2000);

    analogWrite(en2, 255);

    delay(2000);

}