when doing the init() we must use the reference frequency, not the
current frequency. Using the current frequency leaves us with an
incorrect value for Q. If the current frequency is below the reference
frequency (which shouldn't happen in 4.5, but has been seen in 4.3)
then the Q can be much too low and massive phase lag can happen.
The vulnerability in 4.5.x is that the current frequency could be well
above the reference frequency. For example, the user may be doing a
motor test at 30s after boot, which is when we stop the
sensors_converging() test, and thus is the last time we call
init(). In that case we can end up with a Q which is much larger than
the one that should come from INS_HNTCH_FREQ and INS_HNTCH_BW, and
thus end up with a filter that produces a lot less attenuation than is
desired, potentially leading to instability due to high noise.
There are other scenarios that can cause this - for example a motor
test of a fwd motor at 30s after boot, or a spurious FFT peak due to
someone knocking the aircraft, or the vibration of a IC engine.
If the Gyro/Accel ID is already in the registered list, do not try to add it again.
This stops an issue seen on a CubeOrangePlus BG3 where, during the very first boot after a parameter wipe, software incorrectly registers a fourth IMU.
The Fourth IMU is registered because the AUX IMU is the same DevID as the third ICM45686.
INS_TCAL_OPTIONS parameter description indicates a singular bit in a bitmask to persist Accels/TCAL parameters, however there are two separate bits for persistence.
this is for supporting external visual odomotry systems which need the
IMU data to correctly process image data
# Conflicts:
# libraries/AP_InertialSensor/AP_InertialSensor.cpp
we use the instance numbers during filter configuration to check if
fast sampling is enabled. We need to ensure these instance numbers
have been setup before the filtering functions get called
selectively apply filters twice to make sure that FFT is not tracking itself
clean-up notch disablement for non-DSP builds
use filter gyro data for FFT when analysing post-filter
always apply LPF after all of the notches
move to a phased application of window information for FFT
tap FFT gyro window at the appropriate place for downsampled FFTs
add accessor for FFT notch
document notch uses cases and flow
