🛠 Piloter un ruban WS2812 sans bloquer le CPU : WS2812Serial et OctoWS2811

Objectives

The Teensy is THE reference for lighting installations. Two PJRC libraries compete advantageously: WS2812Serial (up to 8 non-blocking instances, each on a UART port used as a DMA waveform generator) and OctoWS2811 (DMA refresh at a video rate of 30 Hz — and on the Teensy 4.0, "supports use of any number of digital pins", so we are no longer limited to the 8 pins of the Teensy 3.x). This tutorial uses WS2812Serial: your sketch continues to run at full speed while the DMA sends the frames.

Hardware

• 1 Teensy 4.0 + WS2812B strip (e.g., 60 LEDs/m)
• DEDICATED 5 V power supply for the strip (60 white LEDs at full brightness ≈ 3.6 A: USB is not enough) — common grounds with the Teensy
• 300–470 Ω resistor in series on the data line, 1000 µF / 6.3 V capacitor across the strip terminals
• Library: https://github.com/PaulStoffregen/WS2812Serial

Complete Code

// Arc-en-ciel défilant, envoi par DMA non bloquant.
#include <WS2812Serial.h>

const uint32_t NUM_LEDS = 60;
byte drawingBuffer[NUM_LEDS * 3];   // RGB, un octet par canal
// Broche 1 sur T4 = TX de Serial1. Serial1/3/4/6/7/8 → jusqu'à 8 instances.
WS2812Serial myLEDs(NUM_LEDS, drawingBuffer, 1, 20, WS2812_SERIAL_DEFAULT);

void setup { myLEDs.begin; }

void loop {
  static uint8_t hue = 0;
  for (uint32_t i = 0; i < NUM_LEDS; i++) {   // remplissage du buffer
    uint8_t h = hue + (i * 256 / NUM_LEDS);
    uint8_t r = (h < 85) ? 255 - h * 3 : (h < 170) ? (h - 85) * 3 : 0;
    uint8_t g = (h < 85) ? h * 3 : (h < 170) ? 255 : 255 - (h - 170) * 3;
    uint8_t b = (h < 85) ? 0 : (h < 170) ? 255 - (h - 85) * 3 : (h - 170) * 3;
    drawingBuffer[i * 3 + 0] = g;   // le WS2812 veut de l'ordre GRB
    drawingBuffer[i * 3 + 1] = r;
    drawingBuffer[i * 3 + 2] = b;
  }
  myLEDs.show(false);   // false = retour immédiat : le DMA envoie
  hue += 4;             // l'animation tourne à pleine vitesse CPU
  delay(20);
}

Expected Verification

The rainbow scrolls at 50 frames/s. Non-blocking test: add a counter Serial.println(millis) in loop — it scrolls normally WHILE the LED frames are being sent, proving that the DMA works on its own. For a massive installation (HUB75 RGB 32x16 panels up to 128x64), look instead at SmartMatrix + the SmartLED v5 shield; for strips driven at a 30 Hz video rate, OctoWS2811.

Common Errors

• Powering the strip from the Teensy's 5 V: a few LEDs work, but a whole strip causes the voltage to drop and restarts the board — use a dedicated external power supply, with grounds connected.
• Forgetting the GRB order: the buffer draws in RGB, but the WS2812 frame is GRB — red and green are swapped, this is the trap.
• Confusing the libraries: WS2812Serial occupies one UART per instance (max 8); OctoWS2811 uses dedicated GPIO pins with continuous DMA video refresh.
• Data on a pin that is not the TX of an eligible UART: check the pin/UART mapping (Serial1/3/4/6/7/8 on the 4.0).
• Frame cut off by blocking code elsewhere: with show(false), do not rewrite the drawingBuffer while the DMA is reading — wait or use double-buffering.
• Data cable too long without a resistor: random glitches on the first LEDs — the series resistor on the Teensy side is your friend.