nodemcu-firmware/docs/modules/ws2812.md

WS2812 Module

Since	Origin / Contributor	Maintainer	Source
2015-02-05	Till Klocke, Thomas Soëte	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)

ws2812.init(mode)

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

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.

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
• ws2812.buffer see Buffer module

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

Buffer module

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 ws2812 library offers a read/write buffer. This buffer has a __tostring method so that it can be printed. This is useful for debugging.

Example

Led chaser with a RGBW strip

ws2812.init()
local i, buffer = 0, ws2812.newBuffer(300, 4); buffer:fill(0, 0, 0, 0); tmr.alarm(0, 50, 1, function()
        i=i+1
        buffer:fade(2)
        buffer:set(i%buffer:size()+1, 0, 0, 0, 255)
        ws2812.write(buffer)
end)

ws2812.newBuffer()

Allocate a new memory buffer to store led values.

Syntax

ws2812.newBuffer(numberOfLeds, bytesPerLed)

Parameters

• numberOfLeds length of the led strip
• bytesPerLed 3 for RGB strips and 4 for RGBW strips

Returns

ws2812.buffer

ws2812.buffer:get()

Return the value at the given position

Syntax

buffer:get(index)

Parameters

• index position in the buffer (1 for first led)

Returns

(color)

Example

buffer = ws2812.newBuffer(32, 4)
print(buffer:get(1))
0	0	0	0

ws2812.buffer:set()

Set the value at the given position

Syntax

buffer:set(index, color)

Parameters

• index position in the buffer (1 for the first led)
• color payload of the color

Payload could be:

• number, number, ... you should pass as many arguments as bytesPerLed
• table should contains bytesPerLed numbers
• string should contains bytesPerLed bytes

Returns

nil

Example

buffer = ws2812.newBuffer(32, 3)
buffer:set(1, 255, 0, 0) -- set the first led green for a RGB strip

buffer = ws2812.newBuffer(32, 4)
buffer:set(1, {0, 0, 0, 255}) -- set the first led white for a RGBW strip

buffer = ws2812.newBuffer(32, 3)
buffer:set(1, string.char(255, 0, 0)) -- set the first led green for a RGB strip

ws2812.buffer:size()

Return the size of the buffer in number of leds

Syntax

buffer:size()

Parameters

none

Returns

int

ws2812.buffer:fill()

Fill the buffer with the given color. The number of given bytes must match the number of bytesPerLed of the buffer

Syntax

buffer:fill(color)

Parameters

• color bytes of the color, you should pass as many arguments as bytesPerLed

Returns

nil

Example

buffer:fill(0, 0, 0) -- fill the buffer with black for a RGB strip

ws2812.buffer:dump()

Returns the contents of the buffer (the pixel values) as a string. This can then be saved to a file or sent over a network.

Syntax

buffer:dump()

Returns

A string containing the pixel values.

Example

local s = buffer:dump() 

ws2812.buffer:replace()

Inserts a string (or a buffer) into another buffer with an offset. The buffer must have the same number of colors per led or an error will be thrown.

Syntax

buffer:replace(source[, offset])

Parameters

• source the pixel values to be set into the buffer. This is either a string or a buffer.
• offset the offset where the source is to be placed in the buffer. Default is 1. Negative values can be used.

Returns

nil

Example

buffer:replace(anotherbuffer:dump()) -- copy one buffer into another via a string
buffer:replace(anotherbuffer) -- copy one buffer into another
newbuffer = buffer.sub(1)     -- make a copy of a buffer into a new buffer

ws2812.buffer:mix()

This is a general method that loads data into a buffer that is a linear combination of data from other buffers. It can be used to copy a buffer or, more usefully, do a cross fade. The pixel values are computed as integers and then range limited to [0, 255]. This means that negative factors work as expected, and that the order of combining buffers does not matter.

Syntax

buffer:mix(factor1, buffer1, ...)

Parameters

• factor1 This is the factor that the contents of buffer1 are multiplied by. This factor is scaled by a factor of 256. Thus factor1 value of 256 is a factor of 1.0.
• buffer1 This is the source buffer. It must be of the same shape as the destination buffer.

There can be any number of factor/buffer pairs.

Returns

nil

Example

-- loads buffer with a crossfade between buffer1 and buffer2
buffer:mix(256 - crossmix, buffer1, crossmix, buffer2)

-- multiplies all values in buffer by 0.75
-- This can be used in place of buffer:fade
buffer:mix(192, buffer)

ws2812.buffer:power()

Computes the total energy requirement for the buffer. This is merely the total sum of all the pixel values (which assumes that each color in each pixel consumes the same amount of power). A real WS2812 (or WS2811) has three constant current drivers of 20mA -- one for each of R, G and B. The pulse width modulation will cause the average current to scale linearly with pixel value.

Syntax

buffer:power()

Returns

An integer which is the sum of all the pixel values.

Example

-- Dim the buffer to no more than the PSU can provide
local psu_current_ma = 1000
local led_current_ma = 20
local led_sum = psu_current_ma * 255 / led_current_ma

local p = buffer:power()
if p > led_sum then
  buffer:mix(256 * led_sum / p, buffer) -- power is now limited
end

ws2812.buffer:fade()

Fade in or out. Defaults to out. Multiply or divide each byte of each led with/by the given value. Useful for a fading effect.

Syntax

buffer:fade(value [, direction])

Parameters

• value value by which to divide or multiply each byte
• direction ws2812.FADE_IN or ws2812.FADE_OUT. Defaults to ws2812.FADE_OUT

Returns

nil

Example

buffer:fade(2)
buffer:fade(2, ws2812.FADE_IN)

ws2812.buffer:shift()

Shift the content of (a piece of) the buffer in positive or negative direction. This allows simple animation effects. A slice of the buffer can be specified by using the standard start and end offset Lua notation. Negative values count backwards from the end of the buffer.

Syntax

buffer:shift(value [, mode[, i[, j]]])

Parameters

• value number of pixels by which to rotate the buffer. Positive values rotate forwards, negative values backwards.
• mode is the shift mode to use. Can be one of ws2812.SHIFT_LOGICAL or ws2812.SHIFT_CIRCULAR. In case of SHIFT_LOGICAL, the freed pixels are set to 0 (off). In case of SHIFT_CIRCULAR, the buffer is treated like a ring buffer, inserting the pixels falling out on one end again on the other end. Defaults to SHIFT_LOGICAL.
• i is the first offset in the buffer to be affected. Negative values are permitted and count backwards from the end. Default is 1.
• j is the last offset in the buffer to be affected. Negative values are permitted and count backwards from the end. Default is -1.

Returns

nil

Example

buffer:shift(3)

ws2812.buffer:sub()

This implements the extraction function like string.sub. The indexes are in leds and all the same rules apply.

Syntax

buffer1:sub(i[, j])

Parameters

• i This is the start of the extracted data. Negative values can be used.
• j this is the end of the extracted data. Negative values can be used. The default is -1.

Returns

A buffer containing the extracted piece.

Example

b = buffer:sub(1,10)

ws2812.buffer:__concat()

This implements the .. operator to concatenate two buffers. They must have the same number of colors per led.

Syntax

buffer1 .. buffer2

Parameters

• buffer1 this is the start of the resulting buffer
• buffer2 this is the end of the resulting buffer

Returns

The concatenated buffer.

Example

ws2812.write(buffer1 .. buffer2)