16. LED Brightness Control Using PWM

How do you plan to solve it?

// Fade an LED using PWM
int ledPin = 9; // Pin with PWM (marked ~ on Arduino Uno)

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

void loop() {
  // Increase brightness
  for (int brightness = 0; brightness <= 255; brightness++) {
    analogWrite(ledPin, brightness); // Set PWM duty cycle
    delayMicroseconds(7812);
  }

  // Decrease brightness
  for (int brightness = 255; brightness >= 0; brightness--) {
    analogWrite(ledPin, brightness);
    delayMicroseconds(3906);
  }
}

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