🛠 Faire clignoter une LED avec l'ESP8266-ESP-12E

Objectives

Discover the ESP8266-ESP-12E board by making an LED blink. This first setup helps you understand the 3.3 V power supply requirement only (never 5 V on this board!), the role of the CH_PD pin (or the module's VCC) which must be connected to 3.3 V for the module to start, and the principle of the GPIO2 pin: it must remain high at startup, which is the case with an LED and its resistor connected to ground. The module has only one Xtensa core: the entire program runs sequentially.

Materials

• 1 ESP8266-ESP-12E module (or ESP-12E development board with 3.3 V regulator)
• 1 LED
• 1 resistor of 220 Ω to 330 Ω
• 1 stable 3.3 V power supply (capable of providing approximately 250 mA peak)
• Connecting wires, breadboard

Complete code

// Clignotement LED sur GPIO2 (broche D4 sur cartes NodeMCU)
const uint8_t LED_PIN = 2;

void setup {
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);   // LED éteinte au repos
}

void loop {
  digitalWrite(LED_PIN, HIGH);  // LED allumée
  delay(500);
  digitalWrite(LED_PIN, LOW);   // LED éteinte
  delay(500);
}

Expected verification

The LED blinks once per second (500 ms on, 500 ms off). On most ESP-12E modules, the onboard LED is indeed on GPIO2: the setup therefore works even without an external LED. If the module does not start at all (silent serial port, no boot message), first check that CH_PD is properly connected to 3.3 V.

Common errors

• Powering the module with 5 V: the ESP8266 operates exclusively at 3.3 V, 5 V can destroy it.
• Forgetting to connect CH_PD to 3.3 V: the module remains off, no message on the console.
• Placing the LED on GPIO0 with a low resistance: GPIO0 must remain high at startup, otherwise the module enters flash mode and the program does not start.
• Forgetting the series resistor with the LED, which overloads the pin.