Skip to content

HardFOC driver · ESP32

WS2812 RMT Driver

A C++ driver for WS2812 and WS2812B addressable LEDs (NeoPixels) on the ESP32 family. It keeps a pixel buffer, scales brightness, encodes every bit as an RMT symbol and lets the RMT peripheral time the pulses, so the CPU never bit-bangs the line. Animation effects and multi-strip coordination come with it.

Quickstart API guide Source on GitHub

The driver is ESP-IDF code. Unlike the other HardFOC drivers it has no platform port: it calls ESP-IDF's RMT driver directly, so it runs on ESP32 chips with an RMT peripheral and ESP-IDF v5.3 or later, and nowhere else. Porting explains what that means for other targets.

Addressable RGB LED with integrated driver WS2812B Worldsemi (also WS2812)
Interface
One data line, NRZ at 800 kbit/s; 24 bits per LED, green-red-blue, MSB first
Bit timing
T0H 0.4 µs, T1H 0.8 µs, T0L 0.85 µs, T1L 0.45 µs, each ±150 ns; reset: low for more than 50 µs (the driver sends 300 µs, enough for the WS2812B-V5)
Supply
VDD 3.5 V to 5.3 V
Input levels
High at 0.7 × VDD or more, low at 0.3 × VDD or less: 3.5 V and 1.5 V at VDD = 5 V
Package
5050 (5.0 mm × 5.0 mm), 4 pins: VDD, DOUT, VSS, DIN
What the driver uses
One RMT transmit channel at 10 MHz (100 ns per tick), one GPIO, a blocking transmit per frame

WS2812B datasheet · WS2812 datasheet

What you get

  • One object per strip. WS2812Strip owns an RMT channel, the pixel buffer and the timing; SetPixel() and Show() are the whole loop. See the API guide.
  • Hardware timing. Each bit becomes one RMT symbol with the high and low times you configure, in 100 ns steps. See Signal timing.
  • Brightness without losing your colours. SetBrightness() scales at send time; the stored pixels stay as you wrote them.
  • RGB and RGBW. 24 or 32 bits per LED, chosen per strip.
  • Effects. Rainbow, chase, blink, breath, Larson scanner and solid colour, one Tick() per frame, and WS2812MultiAnimator to keep several strips in step. See Architecture.
  • Tested without hardware. Host unit tests run the real driver sources against a recording fake of the RMT driver. See Testing and CI.

Where to go next

  • Quickstart

    Wire a strip, add the component, light it in about 15 lines.

  • Hardware

    Pins, level shifting, power and the bit timing from the datasheet.

  • Architecture

    From pixels to RMT symbols: the layers and what each one owns.

  • API guide

    Create a strip, set pixels, animate, handle errors, task by task.

  • Signal timing

    Ticks, frame time, memory and the reset gap.

  • API reference

    Every class and member, generated from the headers.