Datasheet

Preliminary Data Sheet

BMA400

Page 24 /

Confidential

BST-BMA400-DS000-00 | Version 0.1 | November 2017 Bosch Sensortec

BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice.

 Reference update mode (configured by setting WKUP_INT_CONFIG0.wkup_refu)

wkup_refu<1:0>

description of auto-wake references update mode

b00

manual update

The references (int_wkup_refX/Y/Z) are not updated

automatically, they shall be set manually by user

b01

one time

The references is updated every time at entering low power

mode. The first measured acceleration in Low-power mode is

used as reference.

b10 or b11

every time

The reference is updated every time after the acceleration

conversion in low-power mode

The reference values are 8-bit signed values. The activity measurement takes the upper 8

bits of the acceleration value and compares against the reference

WKUP_INT_CONFIG[2-4].int_wkup_ref[x,y,z].

 Threshold for activity detection: the threshold for activity detection (comparison of the

difference between the measured acceleration data and reference acceleration data) has 8-bit

resolution, corresponding to the upper 8 bits of the absolute value of the 12bit acceleration,

WKUP_INT_CONFIG1.int_wkup_thres.

 Number of samples for decision: the number of samples for wake-up decision is configured

between 1 and 8 by the register WKUP_INT_CONFIG0. num_of_samples (number of samples

is the register value + 1).

The condition for activity-driven automatic wake-up from low-power is (assuming all 3 axes are

enabled):

( abs(a_x-ref_x) > thresh_x ) OR ( abs(a_y-ref_y) > thresh_y ) OR( abs(a_z-ref_z) > thresh_z )

This condition must persist for WKUP_INT_CONFIG0. num_of_samples data samples.

Confidential and under NDA

Seeed Studio

Confidential and under NDA

Seeed Studio

Confidential and under NDA