CircuitPython in 2022

CircuitPython is an amazing microcontroller programming platform, running on many different chips and boards while providing a consistent API. I’m pretty experienced with embedded development and Arduino, but have little Python knowledge. So for the last few years I’ve been using CircuitPython to teach myself Python. The results I’ve been logging via my QTPy Tricks and CircuitPython Tricks repos. CircuitPython is one of the most fun and useful tools in my toolkit now.

At the beginning of every year, the community reflects on CircuitPython and their plans for its future. This year the tag is “#CircuitPython2022“. Here are my (belated) plans / desires. My overall theme is: audio stuff!

The Big Ones

These are the large efforts that are year-long in scope and perhaps not even possible. But any would put CircuitPython on an entirely new level of usefulness for me.

• Modular audio engine. The Teensy Audio Library (TAL) is hugely powerful, able to create synthesizers, audio effects, just about anything to do with real-time audio in and out of a microcontroller. It would be amazing to port it to CircuitPython. CirPy already has pretty robust support for DMA-based audio streams, a main stumbling block to get this functionality I think, but I really don’t know if it’s feasible. There does seem to be the beginnings with audiomixer.Mixer and synthio, but I know nothing. From my recent playing with the Mozzi synth library and Teensy Audio Library on SAMD51, I am eager to see if those concepts can be applied to CircuitPython. I expect it’s beyond my abilities but it would be very cool to see CircuitPython being used to describe audio flows to create custom audio devices. See circuitpython#4467 for more
• Periodic code block invocation. So much synth & game code needs regular timing. Example: how would you create a metronome in CircuitPython? Currently one does this by hand by checking time.monotonic() or supervisor.ticks_ms(). This is fine but if you have a displayio display or adafruit_seesaw devices, you are at the mercy of the various delays inherent to those libraries. Yes, this is a variant of the “why no interrupts?” argument, but if it’s periodic and under the control of the CircuitPython supervisor, perhaps the issues can be dealt with?
• USB Host! I’m very excited by some recent additions in TinyUSB that adds a USB MIDI host driver. But how cool would it be to plug in a USB keyboard, MIDI controller, or thumbdrive to a CircuitPython device and have it work? See circuitpython #5630 for more

“Small” Changes

These are issues I’ve experienced or changes I want but haven’t characterized enough to submit an issue. And they’re small enough that maybe I can actually contribute on.

• Allow play start/end points & loop start/end points for audiocore.WaveFile and audiocore.RawSample. Currently you can tell a sample to loop and it works! This is awesome. The looping functionality could be so much more powerful if the start/end points could be modified.
• Allow RawSample buffer to be replaced. Currently once you create a RawSample, it’s read-only.
• Why does audiocore.AudioMixer seem to mess up with multiple small RawSamples?
• The adafruit_seesaw library and its descendants are very conservative about timing with explicit time.sleep() calls to ensure good data. This kills update rate when using several Seesaw devices. I’d like to try tuning these or at least propagating up the delays to the user.
• Newbie-friendly documentation changes for “Core” modules. The docs for the built-in C-based libraries are really good if you know what you’re doing. They function well as reference material. But if you’re new to a concept, they can be a bit mystifying. And you can’t look at the Python source because they’re in C. I’ve had this problem a few times and this point is a reminder to myself: when this happens to me again, make a PR with what I think would help.

Projects for 2022

Some projects I plan on doing in CircuitPython in the coming months:

• Tiny USB + Serial MIDI keyboard using KB2040 and Kalih key switches. Oh no another CircuitPython keyboard! I always need small MIDI controllers. The OMX-27 I have is great, but I broke its encoder, it’s hard to repair, and I want something smaller. And I’ve not played in the “keeb” space so this’ll be my entrée to that world.
• “Additive synthesis” using stacked RawSamples. In CircuitPython it’s really easy to compute and play samples on the fly. Can I use this to create a kind of wavetable synthesizer by mixing samples through an audioio.AudioMixer?
• Seesaw Knob & Button board. Of the little Seesaw IO expander board’s 15 GPIO pins, 9 can be ADC pins! I want a Seesaw board that has 8 pots, 4 buttons and some NeoPixel / WS2812 LEDs. This seems like it should be a thing? Why isn’t this a thing? I will make it a thing.
• “Tiny LED Effects” library submitted to the CircuitPython_Community_Bundle. This is a small collection of functions I use on QTPy M0 where adafruit_led_animation and adafruit_fancyled will not fit. It’s a neat bunch of generative LED effects with its own optional cutdown version of neopixel, I just need to package it up.

Closing Thoughts

The CircuitPython community is the best I’ve experienced. I feel privileged to be considered part of it. I’m always learning something new about some aspect of Python, different processor architectures, or some new algorithm or technique. If you’re interested in CircuitPython, please join the Discord! I can’t wait to see what 2022 brings.