WS2812 datasheet(71/98 Pages) RASPBERRY-PI

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Tiles don’t need to be square! The above is just one possible layout. The display shown at the top of this page is three

10x8 tiles assembled from NeoPixel strip.

Once the matrix is defined, the remainder of the project is similar to Adafruit_NeoPixel. Remember to use

matrix.begin() in the setup() function and matrix.show() to update the display after drawing. The setBrightness() function

is also available. The library includes a couple of example sketches for reference.

Other Layouts

For any other cases that are not uniformly tiled, you can provide your own function to remap X/Y coordinates to

NeoPixel strip indices. This function should accept two unsigned 16-bit arguments (pixel X, Y coordinates) and return an

unsigned 16-bit value (corresponding strip index). The simplest row-major progressive function might resemble this:

uint16_t myRemapFn(uint16_t x, uint16_t y) {

return WIDTH * y + x;

}

That’s a crude example. Yours might be designed for pixels arranged in a spiral (easy wiring), or a Hilbert curve.

The function is then enabled using setRemapFunction():

matrix.setRemapFunction(myRemapFn);

RAM Again

On a per-pixel basis, Adafruit_NeoMatrix is no more memory-hungry than Adafruit_NeoPixel, requiring 3 bytes of RAM

per pixel. But the number of pixels in a two-dimensional display takes off exponentially…a 16x16 display requires

four

times the memory of an 8x8 display, or about 768 bytes of RAM (nearly half the available space on an Arduino Uno). It

can be anywhere from

tricky to impossible to combine large displays with memory-hungry libraries such as SD or ffft.

Gamma Correction

Because the Adafruit_GFX library was originally designed for LCDs (having limited color fidelity), it handles colors as

16-bit values (rather than the full 24 bits that NeoPixels are capable of). This is not the big loss it might seem. A quirk of

human vision makes bright colors less discernible than dim ones. The Adafruit_NeoMatrix library uses

gamma

correction to select brightness levels that are visually (though not numerically) equidistant. There are 32 levels for red

and blue, 64 levels for green.

https://learn.adafruit.com/adafruit-neopixel-uberguide

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WS2812 Datasheet(PDF) 71 Page - Raspberry Pi Holdings PLC