BMA222 Bosch Sensortec, BMA222 Datasheet - Page 32

• Manufacturer Part Number: BMA222
• Description: 3-AXIS ACCELEROMETER DIGITAL SMD
• Manufacturer: Bosch Sensortec

Specifications of BMA222

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 828-1025-2

4.8.7.1 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 21.
The theta blocking is defined by the following inequality:
The parameter blocking_theta of the above given equation stands for the contents of the (0x2D)
orient_theta bits. Hereby 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.
4.8.8 Flat detection
The flat detection feature gives information about the orientation of the devices´ z-axis relative
to the g-vector, i. e. it recognizes whether the device is in a flat position or not.
The condition for the device to be in the flat position is
Rev. 1.0
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Note: Specifications within this document are subject to change without notice.
Table 21: Blocking conditions for orientation recognition
orient_blocking
(0x2C)
tan
00b
01b
10b
11b


blocking
value of orient is not stable for at least 100 ms
8
_
Data sheet
BMA222
acceleration slope in any axis > 0.2 g
acceleration slope in any axis > 0.4 g
theta
Page 32
.
theta blocking
theta blocking
theta blocking
Conditions
no blocking
or
or
or
Bosch Sensortec
07 March 2011