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First commit of the repo. Contents beyond the v0.1 simulator and layout: - Full Pico 2 W firmware (firmware/app, drivers, engine port, host test). - BANK page and 404 mode A/B removed; learned pads play exactly what was learned. - 404/MiniFreak renamed to KIT/SYNTH throughout (jacks, code, sim, docs, layout labels; wiring rebuilt). - ROLL returns to page select after a re-roll; a freshly learned track turns on. - LCD contrast 66. - ROOT and SCALE pages: 21 scales, AUTO = the seed picks; global and sticky. Intended music change: the scale table grew from 8 to 21 and AUTO picks from all of them, so every seed's scale changed. Vectors regenerated with npm run vectors, plus new key-override cases. Flash record is now version 2. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
4.5 KiB
4.5 KiB
Design decisions
Short record of why things are the way they are, so they don't get undone by accident.
Music
- Tracks are only on or off.
- There's no auto mode. Bringing parts in and out is the performance (Lyon, "Techno Counterpoint").
- Every track is rendered every bar, so muting doesn't change the pattern.
- No break lane. Chopping breaks is the M8's job. Seedbox makes rhythm and melody. AMENIZER is a generator that plays a break pattern on the kit, not a sample player.
- Energy moves hats only a quarter as much as the rest. Before that, energy mostly meant busier hats.
- Rhythmic frames per seed. Before frames, most seeds put the kick on 1 and the snare on 3.
- Sections are transforms of A, not new patterns. The phrase hangs together.
- Drift is continuous overlapping layers, not steps. Wide knob spans used to do little. Drift adds displacement and weirdness at the top end.
- AMENIZER keeps its own feel. Its humanising and chops are tuned so that DRIFT past halfway isn't too extreme. The generic layers come in later and at half strength.
- ROOT and SCALE are global and sticky (2026-10-11). They survive SEED, ROLL and slot loads, so a seed can be fitted to an existing idea. AUTO lets the seed pick from all 21 scales, which changed every seed's sound (vectors regenerated). Slots don't store the key.
- Integer-only engine with a seeded RNG. This makes it deterministic and portable, and testable by golden vectors.
MIDI
- Kit pads are learned, not configured. The bank/pad/mode tables were dropped. BANK was dropped too (2026-10-11): it only made sense for the SP-404MKII's bank layout, and the kit side should work with any sampler or drum machine. Re-learn to change kit.
- STOP sends CC 120 on the kit channels because some samplers (the SP-404MKII) ignore All Notes Off. SPP isn't sent.
- The synth is in poly mode on one channel. Bass, melody and pad share it.
- MIDI OUT follows the 3.3 V spec (CA-033): 10 Ω on TX, 33 Ω on 3.3 V. An earlier draft had them swapped; the independent review caught it.
- Generic kit and synth (2026-10-11). Jacks, screens and docs say KIT and SYNTH, not 404 and MiniFreak. Those two are the test rig, nothing more.
Hardware
- 6N137 for MIDI IN, because that's the part on hand. It's pin-compatible with the 6N138 here except pin 7, which is the enable input and must be high: a link ties it to pin 8, and the 4.7 kΩ pin 7 resistor is gone. C1 (supply bypass) is required and sits right beside the chip. Never fit a 6N138 with that link in place: on a 6N138, pin 7 is the transistor base.
- 3.5 mm TRS MIDI jacks (Type A) instead of 5-pin DIN: the DIN jacks didn't fit the box. Type A TRS gear takes a plain stereo cable; DIN gear gets a Type A adapter.
- The Pico's USB end is at the stripboard edge (its first pin row is strip A), so the box is powered and flashed through a slot in the back wall, with no extension cable.
- 11 momentary track buttons in a diode matrix, with the state shown on the LCD map. Latching or lit buttons weren't available locally, and LEDs would need more pins.
- No FILL button. Dropped after trying the panel; fills still happen on their own in bar 4. The RUN toggle took the free corner of the grid (row 1 / column 4, outside the matrix), and GHOST moved into FILL's matrix slot (row 2 / column 4).
- Nokia 5110 instead of a 0.91" OLED, which was too small to read.
- Landscape panel in an enclosure of about 80 × 150 mm.
- One stripboard in a plastic box, Pico socketed, everything else panel mounted. No standoffs, screws or USB extension.
- GP0/GP4 links run under the Pico between its headers. That keeps them from crossing header pins; it's the reason for the col-13 cut length.
- Pad names P1–P35, not W…, to avoid clashing with strip W.
Process
- The stripboard was reviewed by blind agents with no access to the design reasoning, as well as by
check-layout.js.- First review (30-row DIN board): 6 issues, all fixed, then clean.
- Second review (USB at the edge, TRS jacks): no electrical faults, 12 doc and mechanical findings, all fixed. The biggest was a link note that named the ground strip instead of strip Y. The rest: USB slot height, SEED above R4, and the panel tool defaulting to portrait.
- R4 now lies flat along strip X across a cut at X23, so a normal ¼ W part fits under SEED.
- The re-check came back clean.
- The firmware port happens in Claude Code (this repo), against the golden vectors.