Speed up CircuitPython LED animations 10x! @NeoPixels #CircuitPython @todbot
In many LED animations, you need to apply an operation to all LEDs as fast as possible. Often this is something like “fadeToBlackBy”, i.e. “dim all LEDs by a given amount”. There are some common effects you get by using “fadeToBlackBy” and one other action. For example: the Cylon effect is “Turn an LED on, Fade all LEDs toward black, Go to next LED, Repeat”. A simple firework simulation is “Turn on random LED, Fade all LEDs toward black, Repeat”.
Tod Kurt has used the Python ulab library, a microcontroller friendly subset of the CPython Numpy library, to do more of the number crunching:
Since I don’t come from a normal Python background, I’ve not used much Numpy. But I knew it was great for vector math. And I knew CircuitPython had a minimal version of Numpy called ulab it inherited from Micropython. Even though I’d seen the wonderful ulab learn guide that jepler did, the usefulness of numpy/ulab didn’t sink in. It was only when I was hacking on LED animation speedups did I re-stumble upon ulab. And am I glad I did.
As a test with a simple fire animation (as optimized as best as Tod could make it in normal Python), the results with ulab are striking:
The general technique is to create a “working copy” of the LED data in a ulab array, and use ulab functions as much as possible to modify that working copy. Then at the last possible moment, copy the working copy data to the real LEDs object. It only adds a few lines of code to existing solutions and you get access to all these cool ulab array functions for LED effects!
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