Datasheet

Preliminary Data Sheet
BMA400
Page 45 /
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.
The mentioned reference can be static (user defined) or it can be updated dynamically.
The reference acceleration registers support reference update modes after comparison evaluation has
been done. The mode is set in GEN(1/2)INT_CONFIG0.act_refu
GEN(1/2)INT_CONFIG0.act_refu
Description of reference update mode
b00
no update – reference is statically set by user using
GEN(1/2)INT_CONFIG4/5/6/7/8/9
b01
one time – the reference is updated once by acceleration
data taken from the data source (acc_filt1 or acc_filt2) after
triggering the interrupt
b10
every time – the reference is updated at the end of the
interrupt evaluation, it is taken from the data source
(acc_filt1 or acc_filt2). This mode especially makes sense
for activity detection where a “constantly” increasing
acceleration shall be detected.
b11
every time - the reference is updated at the end of the
interrupt evaluation, it is taken from the data source
acc_filt_lp. Remember the large group delay (1Hz
bandwidth) of acc_filter_lp
As already mentioned, both interrupts can be configured to detect activity or inactivity. This is done
using GEN(1/2)INT_CONFIG1.criterion_sel.
GEN(1/2)INT_CONFIG1.criterion_sel = 0: inactivity detection, referenced acceleration below
threshold
GEN(1/2)INT_CONFIG1.criterion_sel = 1: activity detection, referenced acceleration above threshold
The reference values for each axis are stored in registers GEN(1/2)INT_CONFIGX.int_th_ref(x/y/z),
they are 12-bit signed values.
The threshold value are stored in register GEN(1/2)INT_CONFIGX.gen_int_thres, it is 8-bit unsigned
value, fixed resolution of 8mg for all measurement ranges.
The interrupt supports a configurable duration condition:
GEN(1/2)INT_CONFIGX.gen1_int_dur<15:0> indicates the resolution in data ready ticks. So, the
duration depends on the data rate the selected filter delivers.
GEN(1/2)INT_CONFIG0.data_src
Source for generic interrupt data
0
acc_filt1
1
acc_filt2
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