#define ledPin 4

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(ledPin, OUTPUT);  //輸出LED
}

void loop() {
  for (int i = 0; i < 256; i++) {
    analogWrite(ledPin, i);
    delay(20);
  };
  for (int i = 255; i <-1; i--) {
    analogWrite(ledPin, i);
    delay(20);
  };
}