FAB_LED

FAB_LED Is a Fast Arduino Bit-banging library for addressable LEDs, like WS2812B, APA-104, APA-106, SK6812, etc.

Download

The Library code is on GitHub, as well as up-to-date documentation.

It can be downloaded directly as a zip file.

To install the library, unzip the source files into your Arduino  “libraries” directory, like any other library. Plug a WS2812B LED strip or panel on pin D6 (pin “~6” on Arduino Uno), power it and compile and load the program. IT should cycle different patterns.

Overview

The FAB_LED library has a few benefits attached to it versus other libraries (AdaFruit NeoPixel or FastLED libraries):

  • The low level bit-banging code is written in gcc C, without any inline assembly. This means it should support any CPU frequency, not just the frequencies that I have hardcoded.
  • The LED class supports multiple pixel formats, which provide great flexibility to choose between pixel manipulation convenience and pixel memory size. A pixel can use from 1 bit of memory to 32 bits, using different schemes:
    • 3 uint8_t per pixel (24 bits)
    • One uint32_t word per pixel (32 bits)
    • 1, 2, 4 or 8 bits per pixel mapped to a color palette of 2, 4, 16 or 256 colors
    • One uint16_t word per pixel (16 bits, 5 bits per pixel), with a choice of 3 levels of brightness
    • Separate pixel clear method and a 256-gray levels method allow you to clear or set a LED strip of any size without using up any memory.
  • The methods can be called back to back to duplicate patterns on infinitely long LED strips, tested on a 16MHz Arduino Uno. Timings for the palette method work but are very tight.
  • Alternatively, you can define multiple arrays to draw frames of an animation, and just change which array is drawn at every clock tick. There is no need to re-draw the frames, unlike other LED libraries.
  • Using the class requires nothing more than knowing which port your LED strip is attached to. A physical port on Arduino is 2 elements, the port letter A to F, and the port pin, from 0 to 7.

At this point FAB_LED is not vaporware anymore. It is fully working.

Example

The following example uses the palette routine, using 2 bits per pixels.

  • It uses a color palette taking only 12 bytes of RAM to hold the 4 color values.
  • It defines a 16-pixel pattern which fits in another 4 bytes of RAM.
  • The 16-pixels pattern is sent 11 times in a tight loop, to light up the whole 170-LED strip.

The animation is done by manipulating the palette colors after the tight sendPixel loop:

  • We rotate one of the four colors (blue-green pulse).
  • We blink on/off the red color.

All this uses a total of 16 bytes for the data arrays, and a one page user code loop to animate. The code page is shown as screen capture.

The bottom loop does the display directly, there is no need for a show() routine since it paints the pixels on the fly as soon as sendPixel() is called.

Here’s a video of this code running:

I am adding slowly 2D support. This is my first rendering. I had to put a cloth to diffuse the LEDs to take the photo. It’s an 8×8 pixel board:

photo418910434535516422

Other links

 

Ooh and posting my video I see someone posted how to pipeline data from a USB port directly… I’ll have to look into that, to maybe stream from USB or a SD card! They can handle thousands of LEDs.

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