NeoPixel (using Adafruit_NeoPixel) Affects Stepper Motor (using AccelStepper)

Other Hardware LEDs and Multiplexing
22

Or directly drive the stepper without a library. Or use a different library -- 660steps/sec = 1515us/step which should be long enough to update a pretty big strip of neopixels.

From the Neopixel side, an update of 10 pixels should take 20*30us+50us = 300us which should leave plenty of time for a step. (Adafruit reference)

But this code updates NEO_COUNT times per update() so it takes 3000us per update:

void BlinkyPixel::update()
{
  for (size_t i = 0; i < numPixels(); i++)
  {
    if (millis() >= timer[i].nextUpdateMillis)
    {
      
      if (timer[i].state)
      {
        setPixelColor(i, 0, 0, 0); // off
      }
      else 
      {
        setPixelColor(i, colors[random(sizeof(colors)/sizeof(uint32_t))]); // random colour
        //setPixelColor(i, random(0xFF), random(0xFF), random(0xFF));
      }
      timer[i].state = !timer[i].state;
      timer[i].nextUpdateMillis = millis() + random(MIN_RANDOM_NUM, MAX_RANDOM_NUM);
    }
    show();
  }
}

You could save a lot of time by moving the show() outside the for() loop. And if you set a flag for whether anything triggered inside the loop(), you could trim it further:

void BlinkyPixel::update()
{
  bool dirty = false;
  for (size_t i = 0; i < numPixels(); i++)
  {
    if (millis() >= timer[i].nextUpdateMillis)
    {
      dirty = true;
      if (timer[i].state)
      {
        setPixelColor(i, 0, 0, 0); // off
      }
      else
      {
        setPixelColor(i, colors[random(sizeof(colors) / sizeof(uint32_t))]); // random colour
        //setPixelColor(i, random(0xFF), random(0xFF), random(0xFF));
      }
      timer[i].state = !timer[i].state;
      timer[i].nextUpdateMillis = millis() + random(MIN_RANDOM_NUM, MAX_RANDOM_NUM);
    }
  }
  if (dirty) {
    show();
  }
}

I think those two changes would speed things up considerably. If you rate-limited the checks to every 2ms, it wouldn't be noticeable, and you'd leave plenty of time for the stepping.

There's a lot of tricks you can do to speed up random neopixel blinking:

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