🛠 Fondu de LED avec le PWM LEDC

Objectives

Control the brightness of an LED using the ESP32's LEDC peripheral: PWM is generated by 8 independent channels (with configurable frequency and resolution), unlike a simple digitalWrite. You will learn how to configure a channel, attach it to a pin, and perform a rising and falling fade.

Hardware

• 1 ESP32 DevKit v1 board
• 1 LED + 1 330 Ω resistor
• Jumper wires (GPIO25 → resistor → LED → GND)

Complete code

const uint8_t LED_PIN = 25;   // eviter GPIO2, broche de strapping
const uint8_t CANAL   = 0;    // 0 a 7 sur ESP32

void setup {
  ledcSetup(CANAL, 5000, 8);  // 5 kHz, resolution 8 bits (0..255)
  ledcAttachPin(LED_PIN, CANAL);
}

void loop {
  for (int v = 0; v <= 255; v++) { ledcWrite(CANAL, v); delay(8); }
  for (int v = 255; v >= 0; v--) { ledcWrite(CANAL, v); delay(8); }
}

Expected verification

The LED turns on and off gradually (a smooth fade of approximately 2 seconds per cycle), without visible steps. With an oscilloscope on GPIO25, you observe a 5 kHz square wave whose duty cycle follows the ramp.

Common errors

• analogWrite does not exist in the Arduino-ESP32 2.x core: you must use ledcSetup/ledcAttachPin/ledcWrite.
• LED wired to GPIO2: this is a strapping pin (along with GPIO0 and GPIO12); a load connected to it can disrupt startup. Prefer GPIO25, 26, 27…
• Forgetting the resistor: the LED burns out or the pin supplies too much current.
• Each LEDC channel is a hardware resource limited to 8 on the ESP32: plan your PWM channels in advance.