Data Sheet

October 2017 BNO080 Datasheet 1000-3927
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The FRS record that configures the stability classifier is encoded in the MotionEngine power management and
stability classifier FRS record. The FRS record provides a stable threshold and a duration threshold. The data
from the gyroscope must be below the stable threshold for the duration threshold period for Stable to be declared.
The default values are 1 rad/s and 3s respectively. The static calibration record for the device contains
parameters that describe the noise floor of the gyroscope. Comparison of the gyroscope’s output to the expected
noise of the system allows for a very reliable measure of high stability, such as one might see when the device is
on a table.
Note that the stability detector is lower power than the stability classifier due to the sensors used (accelerometers
currently consume less power than gyroscopes).
2.4.2 Tap Detector
The tap detector evaluates data from the accelerometer and generates an event when either a single or double
tap is detected. The output of the tap detector indicates the axis along which the tap was detected and whether
the tap was a single or a double tap. The axes are aligned to the Android frame of reference (Figure 2-1).
Figure 2-3: Tap detector
2.4.3 Step Detector
The step detector uses data from the accelerometer to detect steps. It will output a value of 1.0 whenever a step
is detected. The step detector has two optimizations, one for wrist worn devices and the second for all other use
cases.
The step detector has built in defaults (listed below). Modification of these values, while not recommended, is
possible. Consultation with Hillcrest is advised.
Configurable options:
• watchSelector: 1 for wrist worn devices, 0 otherwise
• allowTime: max variation of step period. Default value 250ms
• stepMinTime: minimum step period. Default value 300ms
• groupDelay: group delay of the filter. Filtering of accelerometer data is required to ensure accurate
detection of steps, particularly if the accelerometer is rotating with respect to gravity. The group delay of
the filter is a compromise between responsiveness and error accumulation. A value of 90ms is used and
the user is discouraged from modifying this value without consultation with Hillcrest.
• threshold: vertical motion threshold. The threshold in meters below which a step would not be recognized.
Default is 3.1mm
• thresholdWatch: A second threshold used for wrist worn devices. The default value is 0.01
• thresholdNonWatch: A second threshold for devices other than wrist worn. The default value is 1.2x10
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