PWM

 

#define PIN_PWM 9

int brightness = 0;
int step = 5;

void setup() {
  pinMode(PIN_PWM, OUTPUT);
}

void loop() {
  analogWrite(PIN_PWM, brightness);
  
  brightness += step;

  if ((brightness >= 255)|| (brightness <= 0)) {
      step = -step;
  }
  
  delay(10);    // 10 milliseconds
}

출처 : https://www.arduino.cc/en/Tutorial/BuiltInExamples/Fade

Fade