spin12.js

var Neopixel = require('neopixel');

var data = new Uint8Array(4*12);


function hue(p, h, l) {
  h = h % 0x600;
  var r, g, b;
  if (h < 0x100) { r = 0xff; g = h; b = 0; }
  else if (h < 0x200) { r = 0x1ff - h; g = 0xff; b = 0; }
  else if (h < 0x300) { r = 0; g = 0xff; b = h - 0x200; }
  else if (h < 0x400) { r = 0; g = 0x3ff - h; b = 0xff; }
  else if (h < 0x500) { r = h - 0x400; g = 0; b = 0xff; }
  else { r = 0xff; g = 0; b = 0x5ff - h; }
  return rgb(p, (r*l) >> 8, (g*l)>>8, (b*l)>>8);
}


function rgb(p, r, g, b,w) {
  var i = p * 4;
  data[i++] = g|0;
  data[i++] = r|0;
  data[i++] = b|0;
  data[i++] = w|0;
}

var h = 0;
setInterval(function () {
  for (var p = 0; p < 16; p++) {
    hue(p, p*128 + h,64);
  }
  h += 42;
  Neopixel.write(D4, data);
}, 100);