WS2812 Module

Since Origin / Contributor Maintainer Source
2015-02-05 Till Klocke, Thomas So√ęte Till Klocke ws2812.c

ws2812 is a library to handle ws2812-like led strips. It works at least on WS2812, WS2812b, APA104, SK6812 (RGB or RGBW).

The library uses UART1 routed on GPIO2 (Pin D4 on NodeMCU DEVKIT) to generate the bitstream. It can use UART0 routed to TXD0 as well to handle two led strips at the same time.

WARNING: In dual mode, you will loose access to the Lua's console through the serial port (it will be reconfigured to support WS2812-like protocol). If you want to keep access to Lua's console, you will have to use an other input channel like a TCP server (see example)

Caution

This module has an optional dependency to the pixbuf module i.e. it can work without. However, if you compile the firmware without pixbuf the respective features will be missing from this module.

ws2812.init()

Initialize UART1 and GPIO2, should be called once and before write(). Initialize UART0 (TXD0) too if ws2812.MODE_DUAL is set.

Syntax

ws2812.init([mode])

Parameters

  • mode (optional) either ws2812.MODE_SINGLE (default if omitted) or ws2812.MODE_DUAL

In ws2812.MODE_DUAL mode you will be able to handle two strips in parallel but will lose access to Lua's serial console as it shares the same UART and PIN.

Returns

nil

ws2812.write()

Send data to one or two led strip using its native format, which is generally Green, Red, Blue for RGB strips and Green, Red, Blue, White for RGBW strips. (However, ws2812 drivers have been observed wired up in other orders.)

Because this function uses the hardware UART(s), it is able to return and allow Lua to resume execution up to 300 microseconds before the data has finished being sent. If you wish to perform actions synchronous with the end of the data transmission, tmr.delay() for 300 microseconds.

Separately, because this function returns early, back-to-back invocations may not leave enough time for the strip to latch, and so may appear to the ws2812 drivers to be simply writes to a longer LED strip. Please ensure that you have more than 350 microseconds between the return of ws2812.write() to your Lua and the next invocation thereof.

Syntax

ws2812.write(data1, [data2])

Parameters

  • data1 payload to be sent to one or more WS2812 like leds through GPIO2
  • data2 (optional) payload to be sent to one or more WS2812 like leds through TXD0 (ws2812.MODE_DUAL mode required)

Payload type could be:

  • nil nothing is done
  • string representing bytes to send
  • a pixbuf object containing the bytes to send. The pixbuf's type is not checked!

Returns

nil

Example

ws2812.init()
ws2812.write(string.char(255, 0, 0, 255, 0, 0)) -- turn the two first RGB leds to green
ws2812.init()
ws2812.write(string.char(0, 0, 0, 255, 0, 0, 0, 255)) -- turn the two first RGBW leds to white
ws2812.init(ws2812.MODE_DUAL)
ws2812.write(string.char(255, 0, 0, 255, 0, 0), string.char(0, 255, 0, 0, 255, 0)) -- turn the two first RGB leds to green on the first strip and red on the second strip
ws2812.init(ws2812.MODE_DUAL)
ws2812.write(nil, string.char(0, 255, 0, 0, 255, 0)) -- turn the two first RGB leds to red on the second strip, do nothing on the first

Pixbuf support

For more advanced animations, it is useful to keep a "framebuffer" of the strip, interact with it and flush it to the strip.

For this purpose, the pixbuf library offers a read/write buffer and convenient functions for pixel value manipulation.

For backwards-compatibility, pixbuf.newBuffer() is aliased as ws2812.newBuffer(), but this will be removed in the next nodemcu-firmware release.

Example

Led chaser with a RGBW strip

ws2812.init()

i, buffer = 0, pixbuf.newBuffer(300, 4)

buffer:fill(0, 0, 0, 0)

tmr.create():alarm(50, 1, function()
  i = i + 1
  buffer:fade(2)
  buffer:set(i % buffer:size() + 1, 0, 0, 0, 255)
  ws2812.write(buffer)
end)