Two answers to "does the compass app matter for battery life", both yes-ish
and both now fixed.
The driver put the QMC6309 into normal mode at boot and left it there, so it
converted continuously from power-on whether or not anything read it: ~1 mA at
100 Hz / OSR 8, forever, on a 2300 mAh battery. It is now parked in suspend
after configuration and woken on demand, with m9CompassIdleTick() (called from
the M9's existing per-loop branch) suspending it again two seconds after the
last read. Waking is a single register write since suspend preserves the
configuration; the waking call reports "nothing fresh" and the caller's next
poll gets data, which callers already handle because the chip may be absent.
Separately, lv_timer_handler() runs unconditionally, so a Lua app's timer kept
firing while the display slept -- GPS Compass polled the magnetometer at 10 Hz
into a dark screen, which would have held the sensor awake even after the fix
above. The host now skips the tick while the screen is off and resumes on wake;
dt comes from millis(), so an app sees one long frame rather than a broken
clock. Documented on the SDK page.
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>
