Hardware arrives tomorrow, which makes this the blocking work: the appliance
has no console, so without it there is no way to answer "is pixel 0 at the end
I think it is" except by guessing.
Geometric mapping. NOTE_MAP_GEOMETRIC (default on) derives each key from
white-key geometry rather than semitone index: 52 white keys span the strip,
so a white key is LED_COUNT/52 pixels - about 3.38 at 176 LEDs, not 2 - with
black keys on the boundaries. The old linear map drifts within each octave,
worst at F, by up to ~0.87 LEDs (~6mm) even after an optimal offset and scale.
Set NOTE_MAP_GEOMETRIC=0 to restore it.
This exposed a real bug. Under the geometric map adjacent key spans overlap,
because the semitone pitch (~1.7 LEDs) is narrower than LEDS_PER_KEY. The
renderer painted unlit keys black, so a key erased its lit neighbour's pixels.
It now clears once and paints only lit keys. The linear map never overlapped,
so this could not have been found without the geometry change.
LED_OFFSET shifts every key, absorbing where the strip was actually cut and
where the profile ended up. Off-strip pixels are clipped, never wrapped.
Calibration patterns, selected by CC 20, with CC 21/22 setting the pixel for
the walk: ends (orientation and length), octaves (mapping drift), keys (whole
mapping at once), walk (finding LED_OFFSET), all (voltage droop at the far
end). Patterns run at the same brightness ceiling as normal operation, so none
can exceed the current budget the design already allows.
tools/calibrate.sh drives all of it from the PC over ALSA MIDI, and README
carries the six-step procedure in dependency order.
Verified: tests pass across fourteen configurations, now including both
mapping modes and positive, negative and reversed offsets. Both platforms
build clean - pianoled.uf2 for RP2350 and both Circle kernel images - with no
warnings from project sources.
Claude-Session: https://claude.ai/code/session_01TVCB25LBsmeteWvaSMz4Ne
Raspberry Pi supply is unreliable, and Circle is Broadcom-only - there is no
Allwinner or Rockchip support anywhere in its tree, so an Orange Pi is not a
board swap but a restart on an unproven base. RP2040/RP2350 is the better
answer: available, ~$4, and a better fit for this job than the Zero ever was.
Structure. All the visualizer logic moves to src/ and is now
platform-independent, depending only on ILEDStrip (four methods) with MIDI
pushed in via OnMIDIPacket(). Each platform supplies a backend and a main
loop. The Circle build is unchanged in behaviour and still produces both
kernel images.
Pico backend:
- WS2812B from a PIO state machine, which clocks the 1.25us bit cell directly
rather than faking it with 8 SPI bytes per data bit as the Circle build must.
- TinyUSB MIDI 1.0 device. Enumerates as an ordinary ALSA port, as the Circle
gadget does. Packet framing comes from the USB MIDI Code Index Number rather
than being re-derived.
- Mount, unmount, suspend and resume all clear held notes, so a chord held when
the host goes away cannot stay lit.
- Latch spacing is enforced against a timestamp, so a caller cannot start a
frame inside the WS2812B reset window.
Verified: builds clean for both pico (RP2040, 30052 bytes) and pico2 (RP2350,
28284 bytes), no warnings from project sources, and the Circle build still
produces kernel.img and kernel7.img. Tests pass across nine configurations.
Incidental findings. PIO frees both hardware SPI blocks; on a Pi Zero Circle
exposes only one SPI master (DEVICES=1 for RASPPI<4) and the WS2812B driver
monopolises it, so a display and the strip could not coexist there. RP2040/
RP2350 also support USB host and, on the W variants, BLE via btstack - both
of which section 3a records as impossible on Circle.
Also documents a known limitation found while looking at calibration: the
note-to-LED map is linear in semitone index, but a keybed is not. 52 white
keys span the same 1222mm, making one white key ~3.38 LEDs rather than 2. The
error drifts within each octave, worst at F, by up to ~0.87 LEDs (~6mm) even
after an optimal offset and scale. A geometric map would remove it. Not yet
implemented.
Claude-Session: https://claude.ai/code/session_01TVCB25LBsmeteWvaSMz4Ne
prosolis