BMA255 datasheet(35/119 Pages) BOSCH

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BMA255

Data sheet

Page 35

BST-BMA255-DS004-05 | Revision 1.2 | August 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.

For each orientation mode the (0x0C) orient bits have a different meaning as shown in Table 14

to Table 16:

Table 14: Meaning of the (0x0C) orient bits in symmetrical mode

(0x0C)

orient

Name

Angle

Condition

x00

portrait upright

315° <

 < 45°

|acc_y| < |acc_x| - ‘hyst’

and acc_x - ‘hyst’’ ≥ 0

x01

portrait upside down

135° <

 < 225°

|acc_y| < |acc_x| - ‘hyst’

and acc_x + ‘hyst’ < 0

x10

landscape left

45° <

 < 135°

|acc_y| ≥ |acc_x| + ‘hyst’

and acc_y < 0

x11

landscape right

225° <

 < 315°

|acc_y| ≥ |acc_x| + ‘hyst’

and acc_y ≥ 0

Table 15: Meaning of the (0x0C) orient bits in high-asymmetrical mode

(0x0C)

orient

Name

Angle

Condition

x00

portrait upright

297° <

 < 63°

|acc_y| < 2∙|acc_x| - ‘hyst’

and acc_x - ‘hyst’ ≥ 0

x01

portrait upside down

117° <

 < 243°

|acc_y| < 2∙|acc_x| - ‘hyst’

and acc_x + ‘hyst’ < 0

x10

landscape left

63° <

 < 117°

|acc_y| ≥ 2∙|acc_x| + ‘hyst’

and acc_y < 0

x11

landscape right

243° <

 < 297°

|acc_y| ≥ 2∙|acc_x| + ‘hyst’

and acc_y ≥ 0

Table 16: Meaning of the (0x0C) orient bits in low-asymmetrical mode

(0x0C)

orient

Name

Angle

Condition

x00

portrait upright

333° <

 < 27°

|acc_y| < 0.5∙|acc_x| - ‘hyst’

and acc_x - ‘hyst’ ≥ 0

x01

portrait upside down

153° <

 < 207°

|acc_y| < 0.5∙|acc_x| - ‘hyst’

and acc_x + ‘hyst’ < 0

x10

landscape left

27° <

 < 153°

|acc_y| ≥ 0.5∙|acc_x| + ‘hyst’

and acc_y < 0

x11

landscape right

207° <

 < 333°

|acc_y| ≥ 0.5∙|acc_x| + ‘hyst’

and acc_y ≥ 0

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).

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