Datasheet

Color and Brightness Control

Different colors are achieved via Pulse Width Modulation (PWM) on each of the R, G, B

LED. The PIC has a built-in 3-channel, 16-bit PWM peripheral. This allows us to be fancy

and do Gamma correction, which means we are doing a non-linear mapping of the 8-bit

color value we are commanded with to a high resolution 16-bit color, resulting in a much

more natural color gradient compared to a straight linear mapping. The PWM peripheral

runs at about 500Hz. The generated signals switch the constant-current circuit described

above.

Daisy-Chaining

Originally, we have designed the Pixie to support the same serial protocol as the WS28x

family (aka NeoPixel). It worked. However, this compatibility, which was originally

considered a feature has been eventually deemed a drawback: the WS28x protocol doesn’t

easily lend itself to common micro controller peripherals, and in most cases ends up being

bit-banged by the controller, requiring a relative high CPU usage, making it hard to do other