fade_leds is a quick-and-dirty command line utility that controls a strand of WS2812 LEDs hanging off a Raspberry Pi. These LEDs are often sold by Adafruit under the brand name "Neopixels".

To use the utility:

 `fade_leds color-1 color-2 [color...]`

...where each color is a hex string (with or without the leading 0x). The program will immediately display color-1 on all LEDs in the strand, and then will fade into color-2 over a one-second interval, and so on with each color specified, taking one second to transition between each color pair. At the end of execution, the LEDs will be left showing the last color listed.

At the moment everything is hardcoded for my particular setup, using a strand of 5 LEDs and GPIO pin 18 (in "BCM" numbering; that corresponds to pin 12 in "Board" numbering). To change these assumptions, edit the #defines in fade_leds.c. Obviously, in the long term all of these should be made into command line parameters.

The fade_leds utility requires the rpi_ws281x library, available at GitHub. (Only the C library libws2811.a is required from that project -- not the Python stuff.)

Because the LEDs are driven using DMA, this utility must be installed setuid root.

To build:

   make
   sudo make install