const int PA4 = 0;
  const int PA3 = 16;            
  int p1 = 0;

  void setup() {
    Serial.begin(115200);
    pinMode(PA4, INPUT);

    pinMode(PA3, OUTPUT);
  }

  void loop() {
    p1 = analogRead(PA4);
    Serial.println("p1:PA4: ");
    Serial.println(p1);

    int intensity = map(p1, 0, 1024, 0, 255);
    analogWrite(PA3, intensity);
    delay(10);
  }