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README.md 9.68 KiB

Fadecandy

Fadecandy drives addressable LED strips with the WS2811 and WS2812 controllers. These LED strips are common and inexpensive, available from many suppliers for around $0.25 per pixel.

Fadecandy makes it easy to drive these LEDs from anything with USB, and it includes unique algorithms which eliminate many of the common visual glitches you see when using these LEDs.

The LED drive engine is based on Stoffregen's excellent OctoWS2811 library, which pumps out serial data for these LED strips entirely using DMA. This firmware builds on Paul's work by adding:

  • A high performance USB protocol
  • Zero copy architecture with triple-buffering
  • Interpolation between keyframes
  • Gamma and color correction with per-channel lookup tables
  • Temporal dithering
  • A custom PCB with line drivers and a 5V boost converter
  • A fully open source bootloader

These features add up to give very smooth fades and high dynamic range. Ever notice that annoying stair-stepping effect when fading LEDs from off to dim? Fadecandy avoids that using a form of delta-sigma modulation. It rapidly wiggles each pixel's value up or down by one 8-bit step, in order to achieve 16-bit resolution for fades.

Example videos:

Platform

Fadecandy uses the Freescale MK20DX128 microcontroller, the same one used by the Teensy 3.0 board. Fadecandy includes its own PCB design featuring a robust power supply and level shifters. It also includes an open source bootloader compatible with the USB Device Firmware Update spec.