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>
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