Per the approved audio re-architecture (prototype-first): prove the click -> codec ->
transformer-isolated XLR chain on bought boards before any custom PCB, keeping the RP2350
firmware.
- pico-wm8960/code.py: CircuitPython bring-up for Pico 2 + SparkFun WM8960 breakout.
Synthesizes the click (familiar piezo pitches) -> I2S -> WM8960 -> HP/speaker; line-in
monitor hook; stereo/pan ready for polymeter spatialization. Uses the proven adafruit_wm8960
driver (no hand-rolled register driver).
- hardware/PROTOTYPE.md: shopping list, wiring, and bench milestones M1-M5 (M4 = the no-buzz
ground-loop test = acceptance gate).
Key findings baked in:
- Buzz was a ground loop; cure = transformer galvanic isolation, NOT +/-15 V (which was only
studio headroom and is dropped).
- WM8960 needs MCLK (CircuitPython I2SOut doesn't emit it); the SparkFun breakout's onboard
24 MHz oscillator supplies it -> resolves Risk R1 with zero extra parts.
Track-format conformance (node tests/run.mjs) stays green; DSL untouched.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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