BMC156 datasheet(48/141 Pages) BOSCH

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Data sheet

eCompass BMC156

Page 48

BST-BMC156-DS000-01 | Revision 1.0 | July 2014

Bosch Sensortec

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

Note: Specifications within this document are subject to change without notice. Not intended for publication.

In the preceding tables, the parameter ‘hyst’ stands for a hysteresis, which can be selected by

setting the (0x2C) orient_hyst bits. 1 LSB of (0x2C) orient_hyst always corresponds to 62.5 mg,

in any g-range (i.e. increment is independent from g-range setting). It is important to note that by

using a hysteresis ≠ 0 the actual switching angles become different from the angles given in the

tables since there is an overlap between the different orientations.

The most significant bit of the (0x0C) orient bits (which is displayed as an ´x´ in the above given

tables) contains information about the direction of the z-axis. It is set to ´0´ (´1´) if acc_z ≥ 0

(acc_z < 0).

Figure 12 shows the typical switching conditions between the four different orientations for the

symmetrical mode i.e. without hysteresis:

-2

-1.5

-1

-0.5

0.5

1.5

135

180

225

270

315

360

phi

acc_y/acc_x

acc_x/sin(theta)

acc_y/sin(theta)

portrait upright

landscape left

portrait upside

down

landscape right

portrait upright

-2

-1.5

-1

-0.5

0.5

1.5

135

180

225

270

315

360



acc_y/acc_x

acc_x/sin(theta)

acc_y/sin(theta)

portrait upright

landscape left

portrait upside

down

landscape right

portrait upright

Figure 12: Typical orientation switching conditions w/o hysteresis

The orientation interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) orient_en. The

interrupt is generated if the value of (0x0C) orient has changed. It is automatically cleared after

one stable period of the (0x0C) orient value. The interrupt status is stored in the (0x09)

orient_int bit. The register (0x0C) orient always reflects the current orientation of the device,

irrespective of which interrupt mode has been selected. Bit (0x0C) orient<2> reflects the device

orientation with respect to the z-axis. The bits (0x0C) orient<1:0> reflect the device orientation in

the x-y-plane. The conventions associated with register (0x0C) orient are detailed in chapter 5.

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