gex-thesis/ch.unit.npx.tex

\section{NeoPixel Unit}

The NeoPixel unit implements the protocol needed to control a digital \gls{LED} strip with WS2812, WS2811, or compatible \gls{LED} driver chips. The NeoPixel protocol (explained in \cref{sec:theory_neo}) is implemented in software, therefore it is available on any \gls{GPIO} pin of the module.

The color data can be loaded in five different format: as packed bytes (3$\times$8 bits color), or as the little- or big-endian encoding of colors in a 32-bit format: 0x00RRGGBB or 0x00BBGGRR. The 32-bit format is convenient when the colors are already represented as an array of 32-bit integers, e.g., extracted from a screen capture or an image.

\subsection{NeoPixel Configuration}

\begin{inicode}
[NPX:neo@3]
# Data pin
pin=A0
# Number of pixels
pixels=32
\end{inicode}

\subsection{NeoPixel Commands}

\begin{cmdlist}
	0 & \cname{CLEAR}
	Switch all \glspl{LED} off (sets them to black) & \\

	1 & \cname{LOAD}
	Load a sequence of R,G,B bytes
	& \begin{cmdreq}
		\item For each \glspl{LED}:
		\begin{pldlist}
			\cfield{u8} red
			\cfield{u8} green
			\cfield{u8} blue
		\end{pldlist}
	\end{cmdreq} \\

	4 & \cname{LOAD\_U32\_ZRGB}
	Load 32-bit big-endian 0xRRGGBB (0,R,G,B)
	& \begin{cmdreq}
		\cfield{u32[]} color data (big-endian)
	\end{cmdreq} \\

	5 & \cname{LOAD\_U32\_ZBGR}
	Load 32-bit big-endian 0xBBGGRR (0,B,G,R)
	& \begin{cmdreq}
		\cfield{u32[]} color data (big-endian)
	\end{cmdreq} \\

	6 & \cname{LOAD\_U32\_RGBZ}
	Load 32-bit little-endian 0xBBGGRR (R,G,B,0)
	& \begin{cmdreq}
		\cfield{u32[]} color data (little-endian)
	\end{cmdreq} \\

	7 & \cname{LOAD\_U32\_BGRZ}
	Load 32-bit little-endian 0xRRGGBB (B,G,R,0)
	& \begin{cmdreq}
		\cfield{u32[]} color data (little-endian)
	\end{cmdreq} \\

	10 & \cname{GET\_LEN}
	Get number of \glspl{LED} in the strip
	& \begin{cmdresp}
		\cfield{u16} number of \glspl{LED}
	\end{cmdresp} \\

\end{cmdlist}