🛠 Piloter la LED RGB embarquée WS2812 d'une carte RP2040 générique

Objectives

"Generic" RP2040 boards (Waveshare RP2040 Zero, Adafruit Feather/QT Py RP2040, SparkFun Micro RP2040…) often do not have a simple LED like the Pico: they feature an addressable WS2812 ("NeoPixel") LED driven by a single-wire 800 kHz protocol that MicroPython generates via the RP2040's PIO. By the end of this tutorial, you will be able to find the LED pin on YOUR board and set it to any color.

Hardware

• 1 × generic RP2040 board. Common pinouts: GP16 on Waveshare RP2040 Zero (manufacturer page), GP17 on Adafruit Feather RP2040 (manufacturer page) — check your manufacturer's datasheet, this is THE key piece of information to find
• 1 × USB cable (data!): many Zero boards use USB-C
• MicroPython rp2 firmware flashed in BOOTSEL mode (hold BOOT while plugging in, the board appears as a RPI-RP2 drive)

Complete code

# main.py — LED WS2812 embarquée (GP16 Waveshare Zero, GP17 Feather)
import neopixel
from machine import Pin
import time

PIN = 16                      # à adapter à ta carte !
led = neopixel.NeoPixel(Pin(PIN), 1)   # chaîne d'une seule LED

for r, g, b in [(255, 0, 0), (0, 255, 0), (0, 0, 255), (255, 64, 0)]:
    led[0] = (r, g, b)        # tuple (R, G, B) 0..255
    led.write               # la PIO envoie la trame, le CPU est libre
    time.sleep_ms(500)

while True:                   # « arc-en-ciel » rapide
    for i in range(256):
        led[0] = (i, 255 - i, 128)
        led.write
        time.sleep_ms(5)

Expected verification

The LED turns red, green, blue, and orange at 500 ms intervals, then displays a continuous gradient. Unlike a standard LED, nothing blinks "off" between two colors: the LED retains its last frame, because the WS2812 stores its command. If your board has multiple WS2812 LEDs (some badges, QT Py with strobe), pass the actual length to NeoPixel(..., n).

Common errors

• Coding GP25 by "Pico" reflex: generic boards almost never have an LED on GP25 — the WS2812 is on GP16, GP17, or elsewhere depending on the manufacturer.
• Forgetting led.write: the tuple is modified in memory but nothing is sent on the bus.
• Looking for an rp2 module for the LED: the WS2812 uses the standard neopixel module (included in the rp2 firmware), not rp2.StateMachine directly.
• Powering a long strip from the board's regulator: the Zero includes an 800 mA LDO (Waveshare datasheet), but a strip of 100 white LEDs draws ~6 A — separate power supply required.
• LED turning white/pink randomly at boot: RP2040 pins are reconfigured on reset; add led.fill((0,0,0)); led.write at the beginning of your script.