BMA253
Data sheet
Page 37
4.7.7.1 Orientation blocking
The change of the (0x0C) orient value and – as a consequence – the generation of the interrupt
can be blocked according to conditions selected by setting the value of the (0x2C)
orient_blocking bits as described by Table 17.
Table 17: Blocking conditions for orientation recognition
(0x2C)
orient_blocking
Conditions
00b
01b
no blocking
theta blocking
or
acceleration in any axis > 1.5g
theta blocking
or
10b
11b
acceleration slope in any axis > 0.2 g
or
acceleration in any axis > 1.5g
theta blocking
or
acceleration slope in any axis > 0.4 g
or
acceleration in any axis > 1.5g and value of orient is
not stable for at least 100 ms
The theta blocking is defined by the following inequality:
blocking _theta
tan
.
8
The parameter blocking_theta of the above given equation stands for the contents of the (0x2D)
orient_theta bits. It is possible to define a blocking angle between 0° and 44.8°. The internal
blocking algorithm saturates the acceleration values before further processing. As a
consequence, the blocking angles are strictly valid only for a device at rest; they can be
different if the device is moved.
Example:
To get a maximum blocking angle of 19° the parameter blocking_theta is determined in the
following way: (8 * tan(19°) )² = 7.588, therefore, blocking_value = 8dec = 001000b has to be
chosen.
In order to avoid unwanted generation of the orientation interrupt in a nearly flat position (z ~ 0,
sign change due to small movements or noise), a hysteresis of 0.2 g is implemented for the z-
axis, i. e. a after a sign change the interrupt is only generated after |z| > 0.2 g.
4.7.7.2 Up-Down Interrupt Suppression Flag
Per default an orientation interrupt is triggered when any of the bits in register (0x0C) orient
changes state. The BMA253 can be configured to trigger orientation interrupts only when the
BST-BMA253-DS000-01 | Revision 1.0 | August 2015
Bosch Sensortec
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