BMA250 Bosch Sensortec, BMA250 Datasheet - Page 33
Manufacturer Part Number
3-AXIS ACCELEROMETER DIGITAL I/F
Specifications of BMA250
BMA250 - Digital, Triaxial Acceleration Sensor
X, Y, Z
±2g, 4g, 8g, 16g
256LSB/g, 128LSB/g, 64LSB/g, 16LSB/g
Voltage - Supply
1.62 V ~ 3.6 V
8Hz ~ 1kHz
Package / Case
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
For Use With
828-1024 - BMA250 DAUGHTERCARD FOR DEV KIT
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
Like blocking_theta, used with orientation recognition, the parameter_theta stands for a user-
defined setting. In this case the content of the (0x2E) flat_theta bits. The possible flat angles
also range from 0° to 44.8°. To ensure proper operation, parameter_theta has to be less than or
equal to blocking_theta.
The flat interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) flat_en. The flat interrupt
is generated if the flat value has changed and the new value is stable for at least the time given
by the (0x2F) flat_hold_time bits. The flat value is stored in the (0x0C) flat bit if the interrupt is
enabled. This value is ´1´ if the device is in the flat position, it is ´0´ otherwise. The content of
the (0x0C) flat bit is changed only if the interrupt is generated. The interrupt is automatically
cleared after one sample period. Its status is stored in the (0x09) flat_int bit.
If temporary or latched interrupt mode is used, after the generation of the interrupt the changed
(0x0C) flat value is kept fixed as long as the interrupt persists (e. g. until the latch time expires
or the interrupt is reset). After clearing the interrupt, the (0x0C) flat value is only updated with
the next following value change (i.e. with the next occurring interrupt).
The meaning of the (0x2F) flat_hold_time bits can be seen from table 22.
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Note: Specifications within this document are subject to change without notice.
Table 22: Meaning of flat_hold_time
Page 33 / not for publishing
03 March 2011