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Christopher Van HooseandClaude Fable 5
4e6b050cf8
Two faults, one of them mine from an hour ago.
CAL_SECS is 20 s and the M9's default screen timeout is also 20 s. The tick
pause added in 5a4a5a8 stopped the app the instant the screen blanked, which
is the same instant the calibration was due to finish -- so sampling stopped
half way, the auto-finish (inside on_tick) never ran, and the partial sweep was
fitted and saved without complaint. New wada.sys.keep_awake() holds the screen
AND the tick for a measuring app, and is released when the app closes.
The tumbling instruction was wrong too. Hard-iron calibration assumes the
device ROTATES in a uniform field; carrying it through the air also TRANSLATES
it through the field gradients of a laptop and a desk. Measured consequence: a
centre that moved 0.15 G between sessions against a 0.26 G horizontal signal,
i.e. tens of degrees of direction-dependent error -- which is what "it drifts
when rotating" was. The same device rotated flat in one place fitted a circle
to within 4%, so calibration is now exactly that: a 2D circle fit on x/y, which
is the only thing a heading uses.
And a bad fit can no longer be saved silently, which is how the broken one got
in. calib_solve refuses, with a reason, when the turn is partial (each axis
must span >= 1.4r), when the radius is outside Earth's real horizontal range
(0.08-0.45 G), or when the circle is too distorted (residual > 18% of r --
computed in closed form from the sums already collected). The progress line
shows coverage rather than a countdown.
Also: mag_norm is now the HORIZONTAL magnitude, which lets the app say "Hold it
level" when it departs from the calibrated radius -- the tell-tale for tilt,
which is the accuracy ceiling until the IMU is driven.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>