A two-axis magnetic heading assumes the device is level. At this latitude the
field dips ~60 degrees, so the vertical component is 1.6x the horizontal one
and tipping the device leaks it into the pair the heading is made from: about
1.5 degrees of heading per degree of tilt. That is what "it drifts" was once
the calibration was sound -- it was the hand holding it.
Driver: variants/thinknode_m9/M9Imu.{h,cpp}, QMI8658 at 0x6B on the peripheral
bus, accelerometer only (the gyro is most of the power budget and nothing here
needs it): +/-2 g at 62.5 Hz with the low-pass on, soft reset with a 160 ms
wait that covers both die variants, and the same idle-suspend as the compass so
it costs nothing when unused. CTRL1's ADDR_AI bit is set and read back -- with
it clear the burst read silently returns six copies of one byte, which looks
like a working sensor reporting nonsense. HAS_M9_IMU -> CAP_IMU ->
wada.sys.accel(), caps().accel.
Axes MEASURED, not guessed, by holding three attitudes and logging:
flat, screen up z = -1.02 -> +Z into the screen (down)
on bottom edge, top up x = +0.97 -> +X at the top edge (forward)
on left edge, right up y = +1.08 -> +Y at the right edge
So the IMU is already in the aerospace body frame, and it agrees with the
magnetometer's independently measured +Z-into-screen. (Meshtastic's M9 driver
passes both sensors through untransformed and mirrors the heading on the sign
of accel Z, so its compass flips when the device is turned over. Not copied.)
Heading now rotates the field back into the horizontal plane using gravity
(NXP AN4248 / ST AN3192) before taking the angle, and reports the tilt angle;
past 55 degrees it says "too steep to read" rather than lying. Calibration
returns to a 3D fit because tilt compensation needs the vertical offset too --
but the instruction is now "turn it every way ON ONE SPOT", and the
accelerometer VERIFIES it: coverage is measured by how far gravity swung, so a
flat spin is refused by name ("turn it nose over tail") instead of silently
fitting a degenerate sphere. Simulated in the harness against a modelled M9 in
a known attitude: offsets recovered exactly, and the heading holds within 3
degrees through 20 degrees of roll and pitch.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Firmware
- variants/thinknode_m9/M9Compass.{h,cpp}: QMC6309 at 0x7C on the peripheral
bus. Probe by chip id, soft reset with the explicit clear, CTRL2 0x20
(50 Hz, +/-32 G, set/reset on), CTRL1 0x61 (normal, OSR 8/8), read-back
verified. Synchronous read from the Lua host bridge, 1 s cache, lazy
re-probe while the rail-powered part is still in POR, OVFL kept + flagged +
logged. HAS_M9_COMPASS=1 in the env -> new hardware gate CAP_COMPASS.
- src/helpers/WadaNmeaLocationProvider.h: Wadamesh-owned copy of the core
MicroNMEALocationProvider that also exposes RMC speed/course (the core
keeps its parser private; no libdeps patch). M9 target.cpp builds on it,
HAS_GPS_MOTION=1, wadaGpsMotion() for UITask.
- wada.sys.gps(): + alt (m), + speed_kmh/course where the board provides
them (course only while moving -- an empty RMC course parses as 0), and
nil while the user has GPS switched off. wada.sys.compass(): {x,y,z,ovfl}
Gauss, sensor frame, uncalibrated, registered only where CAP_COMPASS;
caps().compass. Calibration, axis mapping and the heading maths live in
the app so they can be adjusted per user without a firmware cut.
- Host: luaHostContactAt reads the RTC once per contacts() walk instead of
once per contact (an I2C transaction each on the M9); pressCb reports
press coordinates in body content space (scroll offset folded in).
App
- deploy/apps/gpscompass/1.0 + apps.json: rotating rose with a fixed index,
live fix readout, bearing/range to a selected contact, magnetometer
heading with hard-iron calibration (C), frame rotate/mirror (O/F, the
M9's sensor orientation is undocumented), GPS-course fallback on every
other board, saturation warning. Not baked into lua_builtin.h on purpose
(CAP_BUILTIN_LUA_APPS also removes the Store > Apps tab).
Verified: M9, V4, V4-R8, T-Deck compile (M9 flash +2 KB); two adversarial
review passes, all confirmed findings fixed; host Lua harness (vendored
Lua, LUA_32BITS) -- calibration recovers a simulated bias exactly, heading
error 0 deg, worst tick ~10k of the 100k budget. Hardware validation list
(axis orientation, bias magnitude, 0x7C ACK) in M9_PORT.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Second 7-dimension adversarially-verified audit over the 08-19 tree.
Headliners: SUB_MAP over a display-only Lua app orphaned the app page
(key-only soft-lock); Back-ladder z-order redesign (CC/power always-
frontmost, confirm-modal deference, Lua key-forward suppressed while a
confirm is up — the send-permission dialog was unanswerable); map pan
flag could go stale across tab jumps/popups; null-close progress rows
now genuinely block the registry dismiss (shared fix); terminal RX
mirror, fullscreen title, wallpaper caption, storage-error guidance
widened to M9; accent/@-mention pickers suppressed (dead chrome on a
touchless board); kb-backlight cache only latches ACKed duties (0xFF
sentinel == duty 255 skipped the first write every boot); deep sleep
actually drops the rails now (display refcount, LEDC pin re-route,
RTC/digital holds) and powers off radio+GPS; TCXO fallback no longer
codifies the disproven 0.0f; RadioLib old-FW patch fail-closes at
link; ENV_SKIP_GPS_DETECT + CORE_DEBUG_LEVEL=0 added to the env.
Full round log in M9_PORT.md 'Audit pass 2 (2026-08-20)'. All four
touch envs (M9, T-Deck, V4-R8, pager) compile clean.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
New board: ThinkNode_M9_companion_radio_touch env, variants/thinknode_m9/
(board glue, LR1110 target, keyboard driver, partitions, M9_PORT.md pin
reference), boards/thinknode_m9.json, device_caps HAS_THINKNODE_M9 block,
HAS_M9_KEYBOARD input path in the touch UI (d-pad focus nav, tab jump keys,
QWERTY typing).
Based on a contributed bring-up patch by ded (SalishMesh), who also remote-
tested every build on a preproduction unit. Hard-won fixes on top of the
patch, each verified on hardware:
- LR1110 radio init -706: preprod chips run transceiver FW 0x0303, which
rejects DriveDiosInSleepMode (0x012A, added in FW 0x0308) that RadioLib
7.x sends unconditionally during begin(). New build-time patch
scripts/build/patch_radiolib_lr11x0.py tolerates it on old FW;
radio_init() prints the chip's device/FW/errors either way.
- TCXO: DIO3 at 3.3 V (the patch's active-oscillator/tcxo=0 theory gave
-707 on hardware).
- Display: rotation 1 (not 3), plus the missing landscape s_ui_rotation
override so LVGL renders 320x240 instead of portrait-into-landscape.
- Keyboard: the controller is a separate ESP32-S2 I2C slave (0x6C) with
addressed registers - reads select register 0x01 first (bare reads
return the HW-version register forever). Boot probe logs the
controller's HW/FW; backlight duty register wired.
- USB pad release: the keyboard bus lives on GPIO20/21 = the S3's native
USB D-/D+ pads, owned from reset by the ROM USB-Serial-JTAG (D+ pullup
on SDA). M9Board::begin() releases them before any bus init.
- GPIO35-37 are octal-PSRAM pins on the S3R8 - never drive them (the
patch's "SD CS = 36" misread package pin 36 = GPIO48; SD is on the
shared SPI bus, support returns with PIN_SD_CS=48 later).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
