Datasheet
Preliminary Data Sheet
BMA400
Page 48 /
Confidential
BST-BMA400-DS000-00 | Version 0.1 | November 2017 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
Activity changed interrupt
The device provides an “activity changed” interrupt. The activity changed interrupt evaluates
acceleration data for a certain activity over a predefined observation period and sets an interrupt after
activity change is detected compared to previously evaluated activity.
The enable signal for this interrupt is INT_CONFIG1.actch_int.
The activity changed interrupt supports data source selection by setting
ACTCH_CONFIG1.actch_data_src bit. The acceleration data source shall be selectable between
acceleration from acc_filt1 and acceleration acc_filt2.
Following steps are performed for activity changed interrupt evaluation:
Evaluation of the current activity parameter: average difference of the dynamic acceleration
with respect to the quasi-static acceleration (low-pass filtered value acc_filt_lp) over a certain
observation period.
Comparison of the currently evaluated activity parameter with last stored activity parameters
(activity parameters for previous observation period): abs(curr_value – last_value) > threshold.
Update / store the activity parameters: curr_value => last_value.
Activity changed status bits (actch_z_int, actch_y_int, actch_x_int): signalize activity changed
for corresponding axes, “1” for activity changed.
Following configurations are supported for activity changed interrupt:
Selectable acceleration axis for evaluation (actch_x_en, actch_y_en, actch_z_en)
Threshold for activity change. The configuration of the activity threshold is defined by
ACTCH_CONFIG0.actch_thres<7:0>
Number of samples of the observation duration. The observation period is defined by the
number of data samples used for the evaluation of the activity parameters. The observation
period is defined by the setting ACTCH_CONFIG1.actch_npts.
ACTH_CONFIG1.actch_npts<3 :0>
Number of samples for observation
0000
32
0001
64
0010
128
0011
256
0100 .. 1111
512
data_src
Description
0
acc_filt1
1
acc_filt2
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Seeed Studio
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