Addressing neopixel via Uint24Array()

[espruino-discuss]

Posted at 2024-03-19 by @MaBecker

Sharing a way how to setup neopixel, set color and send simple patterns - Many thanks to @gfwilliams who mentioned this possibility via Uint24Array().

// load module
var np = require('neopixel');

//  pin data line is attached to
var NPP= D16;

// number of neopixel
var countNP = 100;

// use  Uint24Array  to store an address single pixel
var neopixelStrip = new Uint24Array(countNP);

// set color for  first and last pixel
var color = {r:20,g:0,b:20};
var c = color.g + (color.r << 8) + (color.b << 16);
neopixelStrip[0] = c;
neopixelStrip[countNP-1] = c;

// flip neopixel
np.write(NPP, neopixelStrip.buffer);

Send a pattern all over the neopixel strip

// Solution A
// simple pattern "_  _  Green _  _"
var fiveLEDs = new Uint24Array(5);
fiveLEDs[2] = 30;
// fill buffer with a pattern array and count 
var nps = E.toUint8Array({data:fiveLEDs.buffer,count:20});

// Solution B
// fill buffer with pattern
for ( i = 2; i < countNP; i +=5 ) { neopixelStrip.buffer[i] = 30;

[gfwilliams]

Posted at 2024-03-19 by @gfwilliams

Just a note that E.HSBtoRGB(h,s,b,24) works to get a 24 bit colour value if you ever fancy doing rainbows

[espruino-discuss]

Posted at 2024-03-19 by @MaBecker

Is there a way to optimize var nps = E.toUint8Array({data:fiveLEDs.buffer,count:20}); ?

[gfwilliams]

Posted at 2024-03-20 by @gfwilliams

There isn't anything I'm aware of. Ideally we'd need a new function that allows Espruino's interpreting of those {data,count} blocks to work on existing buffers, but that doesn't exist yet.

Best bet on official boards is to use JIT:

var countNP = 100;
var neopixelStrip = new Uint24Array(countNP);
var fiveLEDs = new Uint24Array(5);
fiveLEDs[2] = 30;

function repeatPattern(strip, pattern, count) { "jit"
  for (var i=0;i<count;i+=5) strip.set(pattern,i);
}

repeatPattern(neopixelStrip, fiveLEDs, countNP);