🛠 Faire clignoter la LED embarquée (elle est derrière la puce Wi-Fi !)

Objectives

Discover the Raspberry Pi Pico W (RP2040 dual-core Cortex-M0+ 133 MHz + Infineon CYW43439 Wi-Fi/BT radio chip) with the classic: blinking the LED. But beware, the Pico W has a unique peculiarity: the user LED is not on a RP2040 GPIO, it is wired to the WL_GPIO0 pin of the CYW43439 Wi-Fi chip. The blink_simple example from the SDK therefore does not work on the Pico W; you must use the wireless driver (picow_blink in pico-examples). You will also learn why GP23, GP24, GP25, and GP29 are not free GPIOs on this board.

Hardware

• 1 × Raspberry Pi Pico W (ref. SCO918, or Pico WH with soldered headers) — not a classic Pico
• 1 × micro-USB data cable
• For the C version: Pico SDK 2.x with PICO_BOARD=pico_w; for the MicroPython version: _picow firmware (includes the cyw43 driver)

Complete code

// picow_blink.ino-like C SDK — la LED est sur WL_GPIO0 du CYW43439
// CMake : pico_stdlib + pico_cyw43_arch_none (pas besoin du réseau ici)
#include "pico/stdlib.h"
#include "pico/cyw43_arch.h"

int main(void) {
    // cyw43_arch_init alimente le CYW43439 (via GP23) et charge son firmware
    if (cyw43_arch_init) {
        return 1;   // impossible d'initialiser la puce radio
    }
    while (true) {
        cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, 1);  // LED ON (WL_GPIO0)
        sleep_ms(250);
        cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, 0);  // LED OFF
        sleep_ms(750);
    }
}
// Équivalent MicroPython (firmware _picow) :
//   from machine import Pin; import time
//   led = Pin("LED", Pin.OUT)   # alias de la broche pilotée via cyw43
//   > 
//   # (souvent cité comme GP23) n'est pas confirmé dans la quickref rp2.

Expected verification

The green LED blinks: on for 250 ms, off for 750 ms. If you had written the "classic Pico" blink using gpio_init(25), nothing blinks — and for good reason: on the Pico W, GP25 is consumed internally (chip-select of the SPI driving the CYW43439) and the LED is elsewhere! That is THE lesson of this tutorial.

Common errors

• Reusing code from a classic Pico on GP25: on the Pico W, GP23/GP24/GP25/GP29 are reserved by the wireless module (power-on, SPI data/IRQ, SPI CS, SPI CLK) — the datasheet excludes them from user GPIOs.
• Compiling for the wrong board: forgetting PICO_BOARD=pico_w (C SDK) or using a MicroPython firmware that is not _picow (without the cyw43 driver, the LED and Wi-Fi are invisible).
• Forgetting cyw43_arch_init: without initializing the driver, cyw43_arch_gpio_put does nothing — the LED is hanging on an unpowered radio chip.
• Believing the board is defective because blink_simple does not blink: this is documented behavior, the official example for the Pico W is picow_blink.
• Voltages: all logic is 3.3 V, not 5 V tolerant, just like on the classic Pico.