On boot (before USB setup, so the flash write cannot disrupt enumeration) the
device mounts the Mass Storage FAT volume and uses it:
- fatfs 0.4 (git rev c4b88477; 0.3.6 needs core_io for no_std) via a read-only
FlashIo over the .filesystem region (reads flash through a black_box ptr).
- If the root-dir volume label is not "PM_G-1" (e.g. a leftover CircuitPython
volume), write an embedded blank PM_G-1 FAT12 template (src/fat_template.bin =
first 7 sectors of mkfs.fat -F12 -S4096 -n PM_G-1; sets both BPB + root-dir
VOLUME_ID label) -> the drive now shows as PM_G-1.
- Read programs.json (LFN) and a tolerant scanner (parse_setlists) turns it into
user set lists appended to the built-ins. Drop programs.json on the drive,
reboot, your grooves appear (B-hold cycles set lists).
Set lists are now a runtime Vec<SetList>{title,items} (built-ins -> owned +
drive); refactored load/next_track/next_setlist/goto_target/prepare_next/sel.
Validated off-bench: a host probe ran fatfs against a real mkfs 4096-sector image
(label + programs.json read confirmed) before flashing.
WRITE-from-device (practice log / settings) is still deferred (the read path is
in; needs a write-back FlashIo).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Rust sibling of pico-scroll/app.py — the PM_G-1 'Grid' 17x7 LED metronome on a
plain RP2040 Pico (thumbv6m, not the Pico 2). LED-first milestone:
- IS31FL3731 driver: vendored bulk 144-byte framebuffer, one I2C block write per
frame (port of the CircuitPython Matrix; the is31fl3731 crate isn't used).
- Polymeter scheduler driven by track-format::schedule::lane_durs (the cross-impl
contract) + per-lane step clocks + tempo ramp + gap-trainer.
- 4-button input (A play/stop·hold=view, B next-track·hold=next-setlist, X/Y tempo).
- Built-in set lists; 3 views: Ticker (default), Grid, Pendulum.
- Ticker (user-designed): name infinite-scrolls left; BPM pinned right rotated 90
CCW = hundreds dot-bar (1 dot/100) + last 2 digits rotated. 130 -> 1 dot + '30'.
- Build scaffolding: rp2040-hal 0.10 + boot2, memory.x, build.sh + uf2.py (RP2040
family id). thumbv6m-none-eabi added to rust/Containerfile. Excluded from the
host workspace like pm-kit. Compiles clean -> 48 KB pm-grid.uf2.
Audio (USB-MIDI; the board has no speaker), live-sync, firmware push, practice log
and playback-flow auto-advance are deferred to the next milestone (as on pm-kit).
Also: delete COORDINATION.md (solo now); docs/rust-port.md updated with pm-grid
status + corrected Grid driver-matrix row.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
