BMA253
Data sheet
Page 34
4.7.7 Orientation recognition
The orientation recognition feature informs on an orientation change of the sensor with respect
to the gravitational field vector ‘g’. The measured acceleration vector components with respect
to the gravitational field are defined as shown in figure 9.
Figure 9: Definition of vector components
Therefore, the magnitudes of the acceleration vectors are calculated as follows:
acc_x = 1g x sin x cos
acc_y = −1g x sin x sin
acc_z = 1g x cos
acc_y/acc_x = −tan
Depending on the magnitudes of the acceleration vectors the orientation of the device in the
space is determined and stored in the three (0x0C) orient bits. These bits may not be reset in
the sleep phase of low-power mode. There are three orientation calculation modes with different
thresholds for switching between different orientations: symmetrical, high-asymmetrical, and
low-asymmetrical. The mode is selected by setting the (0x2C) orient_mode bits as given in
Table 13.
Table 13: Orientation mode settings
(0x2C)
Orientation Mode
orient_mode
00b
01b
10b
11b
symmetrical
high-asymmetrical
low-asymmetrical
symmetrical
BST-BMA253-DS000-01 | Revision 1.0 | August 2015
Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
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