Datasheet for the mux that lets four same-address OLEDs share a bus.
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Sketching a voice in the Teensy Audio design tool
The PJRC Audio System Design Tool lets you wire oscillators, mixers and filters in the browser and then export the C++ declarations. Wire the modulation (LFO into the waveform’s FM input, envelope into the filter’s frequency control) there first; it’s much quicker than finding a missing AudioConnection by ear.
Teensy Audio System Design Tool
Teensy Audio System Design Tool
Patch a voice in the browser, then export the code.