0330.SB0.171 - Bosch Sensortec

BMA255

Data sheet

Page 1

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.

Data sheet

BMA255

Digital, triaxial acceleration sensor

BMA255: Data sheet

Document revision

1.2

Document release date

01 August 2014

Document number

BST-BMA255-DS004-05

Technical reference code(s)

0 273 141 171

Notes

Data in this document are subject to change without notice.

Product photos and pictures are for illustration purposes only and

may differ from the real product’s appearance.

Not intended for publishing

Bosch Sensortec

BMA255

Data sheet

Page 2

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.

BMA255

12 BIT, DIGITAL, TRIAXIAL ACCELERATION SENSOR WITH INTELLIGENT

ON-CHIP MOTION-TRIGGERED INTERRUPT CONTROLLER

Key features

 Ultra-Small package LGA package (12 pins), footprint 2mm x 2mm,

height 0.95mm

 Digital interface SPI (4-wire, 3-wire), I²C, 2 interrupt pins

VDDIO voltage range: 1.2V to 3.6V

 Programmable functionality Acceleration ranges ±2g/±4g/±8g/±16g

Low-pass filter bandwidths 1kHz - <8Hz

 On-chip FIFO Integrated FIFO with a depth of 32 frames

 On-chip interrupt controller Motion-triggered interrupt-signal generation for

- new data

- any-motion (slope) detection

- tap sensing (single tap / double tap)

- orientation recognition

- flat detection

- low-g/high-g detection

- motion inactivity detection

 Ultra-low power Low current consumption, short wake-up time,

advanced features for system power management

 Temperature sensor

 RoHS compliant, halogen-free

Typical applications

 Display profile switching

 Menu scrolling, tap / double tap sensing

 Gaming

 Pedometer / step counting

 Free-fall detection

 E-compass tilt compensation

 Drop detection for warranty logging

 Advanced system power management for mobile applications

General description

The BMA255 is a triaxial, low-g acceleration sensor with digital output for consumer

applications. It allows measurements of acceleration in three perpendicular axes. An evaluation

circuitry (ASIC) converts the output of a micromechanical acceleration-sensing structure

(MEMS) that works according to the differential capacitance principle.

Package and interfaces of the BMA255 have been defined to match a multitude of hardware

requirements. Since the sensor features an ultra-small footprint and a flat package it is

ingeniously suited for mobile applications.

The BMA255 offers a variable VDDIO voltage range from 1.2V to 3.6V and can be programmed

to optimize functionality, performance and power consumption in customer specific applications.

BMA255

Data sheet

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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.

In addition it features an on-chip interrupt controller enabling motion-based applications without

use of a microcontroller.

The BMA255 senses tilt, motion, inactivity and shock vibration in cell phones, handhelds,

computer peripherals, man-machine interfaces, virtual reality features and game controllers.

BMA255

Data sheet

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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.

Index of Contents

1. SPECIFICATION ........................................................................................................................ 8

2. ABSOLUTE MAXIMUM RATINGS .......................................................................................... 11

3. BLOCK DIAGRAM ................................................................................................................... 12

4. FUNCTIONAL DESCRIPTION ................................................................................................. 13

4.1 SUPPLY VOLTAGE AND POWER MANAGEMENT ..................................................................... 13

4.2 POWER MODES ................................................................................................................. 14

4.3 SENSOR DATA .................................................................................................................. 18

4.3.1 ACCELERATION DATA ....................................................................................................................18

4.3.2 TEMPERATURE SENSOR ............................................................................................................... 19

4.4 SELF-TEST ....................................................................................................................... 20

4.5 OFFSET COMPENSATION ................................................................................................... 21

4.5.1 SLOW COMPENSATION ..................................................................................................................23

4.5.2 FAST COMPENSATION ....................................................................................................................23

4.5.3 MANUAL COMPENSATION ...............................................................................................................24

4.5.4 INLINE CALIBRATION ......................................................................................................................24

4.6 NON-VOLATILE MEMORY .................................................................................................... 25

4.7 INTERRUPT CONTROLLER .................................................................................................. 26

4.7.1 GENERAL FEATURES .................................................................................................................... 26

4.7.2 MAPPING TO PHYSICAL INTERRUPT PINS (INTTYPE TO INT PIN#)......................................................27

4.7.3 ELECTRICAL BEHAVIOUR (INT PIN# TO OPEN-DRIVE OR PUSH-PULL) ................................................28

4.7.4 NEW DATA INTERRUPT ...................................................................................................................28

4.7.5 SLOPE / ANY-MOTION DETECTION ................................................................................................. 29

4.7.6 TAP SENSING ................................................................................................................................31

4.7.7 ORIENTATION RECOGNITION ..........................................................................................................34

4.7.8 FLAT DETECTION .......................................................................................................................... 39

4.7.9 LOW-G INTERRUPT ....................................................................................................................... 40

4.7.10 HIGH-G INTERRUPT .....................................................................................................................41

4.7.11 NO-MOTION / SLOW MOTION DETECTION .......................................................................................42

4.8 SOFTRESET ...................................................................................................................... 44

5. FIFO OPERATION ................................................................................................................... 45

5.1 FIFO OPERATING MODES ................................................................................................. 45

5.2 FIFO DATA READOUT ....................................................................................................... 46

5.3 FIFO FRAME COUNTER AND OVERRUN FLAG ..................................................................... 46

5.4 FIFO INTERRUPTS ............................................................................................................ 47

BMA255

Data sheet

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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.

6. REGISTER DESCRIPTION ...................................................................................................... 48

6.1 GENERAL REMARKS .......................................................................................................... 48

6.2 REGISTER MAP ................................................................................................................. 49

REGISTER 0X00 (BGW_CHIPID) ............................................................................................ 50

REGISTER 0X02 (ACCD_X_LSB) ........................................................................................... 50

REGISTER 0X03 (ACCD_X_MSB) .......................................................................................... 51

REGISTER 0X04 (ACCD_Y_LSB) ........................................................................................... 52

REGISTER 0X05 (ACCD_Y_MSB) .......................................................................................... 53

REGISTER 0X06 (ACCD_Z_LSB) ........................................................................................... 54

REGISTER 0X07 (ACCD_Z_MSB) .......................................................................................... 55

REGISTER 0X08 (ACCD_TEMP) ............................................................................................ 56

REGISTER 0X09 (INT_STATUS_0) ......................................................................................... 57

REGISTER 0X0A (INT_STATUS_1) ........................................................................................ 58

REGISTER 0X0B (INT_STATUS_2) ........................................................................................ 59

REGISTER 0X0C (INT_STATUS_3) ........................................................................................ 60

REGISTER 0X0E (FIFO_STATUS) .......................................................................................... 61

REGISTER 0X0F (PMU_RANGE) ............................................................................................ 62

REGISTER 0X10 (PMU_BW) ................................................................................................... 62

REGISTER 0X11 (PMU_LPW) ................................................................................................. 63

REGISTER 0X12 (PMU_LOW_NOISE) ................................................................................... 64

REGISTER 0X13 (ACCD_HBW) .............................................................................................. 65

REGISTER 0X14 (BGW_SOFTRESET) ................................................................................... 66

REGISTER 0X16 (INT_EN_0) .................................................................................................. 66

REGISTER 0X17 (INT_EN_1) .................................................................................................. 67

REGISTER 0X18 (INT_EN_2) .................................................................................................. 68

REGISTER 0X19 (INT_MAP_0) ............................................................................................... 69

REGISTER 0X1A (INT_MAP_1) ............................................................................................... 70

REGISTER 0X1B (INT_MAP_2)............................................................................................... 71

REGISTER 0X1E (INT_SRC) ................................................................................................... 72

REGISTER 0X20 (INT_OUT_CTRL) ........................................................................................ 73

REGISTER 0X21 (INT_RST_LATCH) ...................................................................................... 74

REGISTER 0X22 (INT_0) ......................................................................................................... 74

REGISTER 0X23 (INT_1) ......................................................................................................... 75

REGISTER 0X24 (INT_2) ......................................................................................................... 75

BMA255

Data sheet

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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.

REGISTER 0X25 (INT_3) ......................................................................................................... 76

REGISTER 0X26 (INT_4) ......................................................................................................... 76

REGISTER 0X27 (INT_5) ......................................................................................................... 77

REGISTER 0X28 (INT_6) ......................................................................................................... 78

REGISTER 0X29 (INT_7) ......................................................................................................... 78

REGISTER 0X2A (INT_8) ........................................................................................................ 79

REGISTER 0X2B (INT_9) ........................................................................................................ 80

REGISTER 0X2C (INT_A) ........................................................................................................ 81

REGISTER 0X2D (INT_B) ........................................................................................................ 82

REGISTER 0X2E (INT_C) ........................................................................................................ 82

REGISTER 0X2F (INT_D) ........................................................................................................ 83

REGISTER 0X30 (FIFO_CONFIG_0)....................................................................................... 84

REGISTER 0X32 (PMU_SELF_TEST) ..................................................................................... 85

REGISTER 0X33 (TRIM_NVM_CTRL) ..................................................................................... 86

REGISTER 0X34 (BGW_SPI3_WDT) ...................................................................................... 87

REGISTER 0X36 (OFC_CTRL) ................................................................................................ 88

REGISTER 0X37 (OFC_SETTING) .......................................................................................... 89

REGISTER 0X38 (OFC_OFFSET_X) ...................................................................................... 90

REGISTER 0X39 (OFC_OFFSET_Y) ....................................................................................... 91

REGISTER 0X3A (OFC_OFFSET_Z) ...................................................................................... 92

REGISTER 0X3B (TRIM_GP0) ................................................................................................ 92

REGISTER 0X3C (TRIM_GP1) ................................................................................................ 93

REGISTER 0X3E (FIFO_CONFIG_1) ...................................................................................... 94

REGISTER 0X3F (FIFO_DATA) ............................................................................................... 95

7. DIGITAL INTERFACES ............................................................................................................ 96

7.1 SERIAL PERIPHERAL INTERFACE (SPI) ................................................................................ 97

7.2 INTER-INTEGRATED CIRCUIT (I²C) .................................................................................... 101

7.2.1 SPI AND I²C ACCESS RESTRICTIONS .......................................................................................... 104

8. PIN-OUT AND CONNECTION DIAGRAM ............................................................................ 105

8.1 PIN-OUT ......................................................................................................................... 105

8.2 CONNECTION DIAGRAM 4-WIRE SPI ................................................................................. 106

8.3 CONNECTION DIAGRAM 3-WIRE SPI ................................................................................. 107

8.4 CONNECTION DIAGRAM I2C .............................................................................................. 108

BMA255

Data sheet

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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.

9. PACKAGE .............................................................................................................................. 109

9.1 OUTLINE DIMENSIONS ..................................................................................................... 109

9.2 SENSING AXES ORIENTATION ........................................................................................... 110

9.3 LANDING PATTERN RECOMMENDATION ............................................................................ 111

9.4 MARKING ....................................................................................................................... 112

9.4.1 MASS PRODUCTION SAMPLES ......................................................................................................112

9.4.2 ENGINEERING SAMPLES ..............................................................................................................112

9.5 SOLDERING GUIDELINES .................................................................................................. 113

9.6 HANDLING INSTRUCTIONS ................................................................................................ 114

9.7 TAPE AND REEL SPECIFICATION ....................................................................................... 115

9.7.1 ORIENTATION WITHIN THE REEL .................................................................................................. 116

9.8 ENVIRONMENTAL SAFETY ................................................................................................ 117

9.8.1 HALOGEN CONTENT ....................................................................................................................117

9.8.2 INTERNAL PACKAGE STRUCTURE .................................................................................................117

10. LEGAL DISCLAIMER .......................................................................................................... 118

10.1 ENGINEERING SAMPLES ................................................................................................ 118

10.2 PRODUCT USE .............................................................................................................. 118

10.3 APPLICATION EXAMPLES AND HINTS ............................................................................... 118

11. DOCUMENT HISTORY AND MODIFICATION ................................................................... 119

BMA255

Data sheet

Page 8

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.

1. Specification

Unless stated otherwise, the given values are over lifetime, operating temperature and voltage

ranges. Minimum/maximum values are ±3.

Table 1: Parameter specification

OPERATING CONDITIONS

Parameter

Symbol

Condition

Min

Typ

Max

Units

Acceleration

Range

gFS2g

Selectable

via serial digital

interface

±2

g

gFS4g

±4

g

gFS8g

±8

g

gFS16g

±16

g

Supply Voltage

Internal Domains

VDD

1.62

2.4

3.6

V

Supply Voltage

I/O Domain

VDDIO

1.2

2.4

3.6

V

Voltage Input

Low Level

VIL

SPI & I²C

0.3VDDIO

-

Voltage Input

High Level

VIH

SPI & I²C

0.7VDDIO

-

Voltage Output

Low Level

VOL

IOL = 3mA, SPI & I²C

0.2VDDIO

-

Voltage Output

High Level

VOH

IOH = 3mA, SPI

0.8VDDIO

-

Total Supply

Current in

Normal Mode

IDD

TA=25°C, bw = 1kHz

VDD = VDDIO = 2.4V

130

µA

Total Supply

Current in

Suspend Mode

IDDsum

TA=25°C

VDD = VDDIO = 2.4V

2.1

µA

Total Supply

Current in

Deep Suspend

Mode

IDDdsum

TA=25°C

VDD = VDDIO = 2.4V

1

µA

Total Supply

Current in

Low-power Mode

1

IDDlp1

TA=25°C, bw = 1kHz

VDD = VDDIO = 2.4V

sleep duration = 25ms

6.5

µA

BMA255

Data sheet

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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.

Total Supply

Current in

Low-power Mode

2

IDDlp2

TA=25°C, bw = 1kHz

VDD = VDDIO = 2.4V

sleep duration = 25ms

66

µA

Total Supply

Current in

Standby Mode

IDDsbm

TA=25°C

VDD = VDDIO = 2.4V

62

µA

Wake-Up Time 1

tw,up1

from Low-power Mode

1 or Suspend Mode or

Deep Suspend Mode

bw = 1kHz

1.3

1.8

ms

Wake-Up Time 2

tw,up2

from Low-power Mode

2 or Stand-by Mode

bw = 1kHz

1

1.2

ms

Start-Up Time

ts,up

POR, bw = 1kHz

3

ms

Non-volatile

memory (NVM)

write-cycles

nNVM

15

cycles

Operating

Temperature

TA

-40

+85

°C

OUTPUT SIGNAL

Parameter

Symbol

Condition

Min

Typ

Max

Units

Sensitivity

S2g

gFS2g, TA=25°C

1024

LSB/g

S4g

gFS4g, TA=25°C

512

LSB/g

S8g

gFS8g, TA=25°C

256

LSB/g

S16g

gFS16g, TA=25°C

128

LSB/g

Sensitivity

Temperature Drift

TCS

gFS2g,

Nominal VDD supplies

±0.02

%/K

Zero-g Offset

Off

gFS2g, TA=25°C, nominal

VDD supplies, over life-

time

±60

mg

Zero-g Offset

Temperature Drift

TCO

gFS2g,

Nominal VDD supplies

±1

mg/K

Bandwidth

bw8

2nd order filter,

bandwidth

programmable

8

Hz

bw16

16

Hz

bw31

31

Hz

bw63

63

Hz

bw125

125

Hz

bw250

250

Hz

bw500

500

Hz

bw1000

1,000

Hz

Nonlinearity

NL

best fit straight line,

gFS2g

±0.5

%FS

BMA255

Data sheet

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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.

Output Noise

Density

nrms

gFS2g, TA=25°C

Nominal VDD supplies

Normal mode

150

µg/Hz

Temperature

Sensor

Measurement

Range

TS

-40

85

°C

Temperature

Sensor Slope

dTS

0.5

K/LSB

Temperature

Sensor Offset

OTS

±2

K

MECHANICAL CHARACTERISTICS

Parameter

Symbol

Condition

Min

Typ

Max

Units

Cross Axis

Sensitivity

S

relative contribution

between any two of

the three axes

1

%

Alignment Error

EA

relative to package

outline

±0.5

°

BMA255

Data sheet

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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.

2. Absolute maximum ratings

Table 2: Absolute maximum ratings

Parameter

Condition

Min

Max

Units

Voltage at Supply Pin

VDD Pin

-0.3

4.25

V

VDDIO Pin

-0.3

4.25

V

Voltage at any Logic Pin

Non-Supply Pin

-0.3

VDDIO+0.3

V

Passive Storage Temp. Range

≤ 65% rel. H.

-50

+150

°C

None-volatile memory (NVM)

Data Retention

T = 85°C,

after 15 cycles

10

y

Mechanical Shock

Duration ≤ 200µs

10,000

g

Duration ≤ 1.0ms

2,000

g

Free fall

onto hard surfaces

1.8

m

ESD

HBM, at any Pin

2

kV

CDM

500

V

MM

200

V

Note:

Stress above these limits may cause damage to the device. Exceeding the specified electrical

limits may affect the device reliability or cause malfunction.

BMA255

Data sheet

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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.

3. Block diagram

Figure 1 shows the basic building blocks of the BMA255:

ADC

TEMP

SENS

Voltage

Regulators

+

Power Control FAST

OSC

SLOW

OSC

Logic

NVM

CSB

SDO

SDI

SCK

PS

INT1

INT2

VDD VDDIO

GND GNDIO

C/V

ADC

C/V

ADC

C/V

Interface

Figure 1: Block diagram of BMA255

BMA255

Data sheet

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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.

4. Functional description

Note: Default values for registers can be found in chapter 6.

4.1 Supply voltage and power management

The BMA255 has two distinct power supply pins:

• VDD is the main power supply for the internal blocks

• VDDIO is a separate power supply pin used for supplying power for the interface

There are no limitations on the voltage levels of both pins relative to each other, as long as

each of them lies within its operating range. Furthermore, the device can be completely

switched off (VDD = 0V) while keeping the VDDIO supply on (VDDIO > 0V) or vice versa.

When the VDDIO supply is switched off, all interface pins (CSB, SDI, SCK, PS) must be kept

close to GNDIO potential.

The device contains a power-on reset (POR) generator. It resets the logic part and the register

values after powering-on VDD and VDDIO. Please note, that all application specific settings which

are not equal to the default settings (refer to 6.2 register map), must be re-set to its designated

values after POR.

There are no constraints on the switching sequence of both supply voltages. In case the I²C

interface shall be used, a direct electrical connection between VDDIO supply and the PS pin is

needed in order to ensure reliable protocol selection. For SPI interface mode the PS pin must

be directly connected to GNDIO.

BMA255

Data sheet

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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.

Low Power

Mode 1

Low Power

Mode 2

NORMAL

Mode

SUSPEND

Mode

DEEP-

SUSPEND

Mode

STANDBY

Mode

Low Power

Mode 1

Low Power

Mode 2

NORMAL

Mode

SUSPEND

Mode

DEEP-

SUSPEND

Mode

STANDBY

Mode

4.2 Power modes

The BMA255 has six different power modes. Besides normal mode, which represents the fully

operational state of the device, there are five energy saving modes: deep-suspend mode,

suspend mode, standby mode, low-power mode 1 and low-power mode 2.

The possible transitions between the power modes are illustrated in figure 2:

Figure 2: Power mode transition diagram

After power-up BMA255 is in normal mode so that all parts of the device are held powered-up

and data acquisition is performed continuously.

In deep-suspend mode the device reaches the lowest possible power consumption. Only the

interface section is kept alive. No data acquisition is performed and the content of the

configuration registers is lost. Deep suspend mode is entered (left) by writing ‘1’ (‘0’) to the

(0x11) deep_suspend bit while (0x11) suspend bit is set to ‘0’. The I2C watchdog timer remains

functional. The (0x11) deep_ suspend bit, the (0x34) spi3 bit, (0x34) i2c_wdt_en bit and the

(0x34) i2c_wdt_sel bit are functional in deep-suspend mode. Equally the interrupt level and

driver configuration registers (0x20) int1_lvl, (0x20) int1_od, (0x20) int2_lvl, and (0x20) int2_od

are accessible. Still it is possible to enter normal mode by performing a softreset as described in

chapter 4.8. Please note, that all application specific settings which are not equal to the default

settings (refer to 6.2 register map), must be re-set to its designated values after leaving deep-

suspend mode.

BMA255

Data sheet

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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.

In suspend mode the whole analog part is powered down. No data acquisition is performed.

While in suspend mode the latest acceleration data and the content of all configuration registers

are kept. Writing to and reading from registers is supported except from the (0x3E)

fifo_config_1, (0x30) fifo_config_0 and (0x3F) fifo_data register. It is possible to enter normal

mode by performing a softreset as described in chapter 4.8.

Suspend mode is entered (left) by writing ´1´ (´0´) to the (0x11) suspend bit after bit (0x12)

lowpower_mode has been set to ‘0’. Although write access to registers is supported at the full

interface clock speed (SCL or SCK), a waiting period must be inserted between two

consecutive write cycles (please refer also to section 7.2.1).

In standby mode the analog part is powered down, while the digital part remains largely

operational. No data acquisition is performed. Reading and writing registers is supported

without any restrictions. The latest acceleration data and the content of all configuration

registers are kept. Standby mode is entered (left) by writing ´1´ (´0´) to the (0x11) suspend bit

after bit (0x12) lowpower_mode has been set to ‘1’. It is also possible to enter normal mode by

performing a softreset as described in chapter 4.8.

In low-power mode 1, the device is periodically switching between a sleep phase and a wake-

up phase. The wake-up phase essentially corresponds to operation in normal mode with

complete power-up of the circuitry. The sleep phase essentially corresponds to operation in

suspend mode. Low-power mode is entered (left) by writing ´1´ (´0´) to the (0x11) lowpower_en

bit with bit (0x12) lowpower_mode set to ‘0’. Read access to registers is possible except from

the (0x3F) fifo_data register. However, unless the register access is synchronised with the

wake-up phase, the restrictions of the suspend mode apply.

Low-power mode 2 is very similar to low-power mode 1, but register access is possible at any

time without restrictions. It consumes more power than low-power mode 1. In low-power mode

2 the device is periodically switching between a sleep phase and a wake-up phase. The wake-

up phase essentially corresponds to operation in normal mode with complete power-up of the

circuitry. The sleep phase essentially corresponds to operation in standby mode. Low-power

mode is entered (left) by writing ´1´ (´0´) to the (0x11) lowpower_en bit with bit (0x12)

lowpower_mode set to ‘1’.

The timing behaviour of the low-power modes 1 and 2 depends on the setting of the (0x12)

sleeptimer_mode bit. When (0x12) sleeptimer_mode is set to ‘0’, the event-driven time-base

mode (EDT) is selected. In EDT the duration of the wake-up phase depends on the number of

samples required by the enabled interrupt engines. If an interrupt is detected, the device stays

in the wake-up phase as long as the interrupt condition endures (non-latched interrupt), or until

the latch time expires (temporary interrupt), or until the interrupt is reset (latched interrupt). If no

interrupt is detected, the device enters the sleep phase immediately after the required number

of acceleration samples have been taken and an active interface access cycle has ended. The

EDT mode is recommended for power-critical applications which do not use the FIFO. Also,

EDT mode is compatible with legacy BST sensors. Figure 3 shows the timing diagram for low-

power modes 1 and 2 when EDT is selected.

BMA255

Data sheet

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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.

State

Sleep phase

Active phase

Sample

tSLEEP

t

Settle

Sample

tSLEEP

tACTIVE

Figure 3: Timing Diagram for low-power mode 1/2, EDT

When (0x12) sleeptimer_mode is set to ‘1’, the equidistant-sampling mode (EST) is selected.

The use of the EST mode is recommended when the FIFO is used since it ensures that

equidistant samples are sampled into the FIFO regardless of whether the active phase is

extended by active interrupt engines or interface activity. In EST mode the sleep time tSLEEP is

defined as shown in Figure 4. The FIFO sampling time tSAMPLE is the sum of the sleep time tSLEEP

and the sensor data sampling time tSSMP. Since interrupt engines can extend the active phase to

exceed the sleep time tSLEEP, equidistant sampling is only guaranteed if the bandwidth has been

chosen such that 1/(2 * bw) = n * tSLEEP where n is an integer. If this condition is infringed,

equidistant sampling is not possible. Once the sleep time has elapsed the device will store the

next available sample in the FIFO. This set-up condition is not recommended as it may result in

timing jitter.

State

Sleep phase

Active phase

Sample

t

Settle

Sample

Settle

Sample

tSLEEP tSLEEP tSLEEP

tSAMPLE tSAMPLE tSAMPLE

Sampled into FIFO

tSSMP

Figure 4: Timing Diagram for low-power mode 1/2, EST

BMA255

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Note: Specifications within this document are subject to change without notice.

The sleep time for lower-power mode 1 and 2 is set by the (0x11) sleep_dur bits as shown in

the following table:

Table 3: Sleep phase duration settings

(0x11)

sleep_dur

Sleep Phase

Duration

tsleep

0000b

0.5ms

0001b

0.5ms

0010b

0.5ms

0011b

0.5ms

0100b

0.5ms

0101b

0.5ms

0110b

1ms

0111b

2ms

1000b

4ms

1001b

6ms

1010b

10ms

1011b

25ms

1100b

50ms

1101b

100ms

1110b

500ms

1111b

1s

The current consumption of the BMA255 in low-power mode 1 (IDDlp1) and low-power mode 2

(IDDlp2) can be estimated with the following formulae:

activesleep

DDactiveDDsumsleep

DDlp tt

ItIt

I





1

.

activesleep

DDactiveDDsbmsleep

DDlp tt

ItIt

I





2

When estimating the length of the wake-up phase tactive, the corresponding typical wake-up time,

tw,up1 or tw,up2 and tut (given in Table 4) have to be considered:

If bandwidth is >=31.25 Hz:

tactive = tut + tw,up1 - 0.9 ms (or tactive = tut + tw,up2 - 0.9 ms)

else:

tactive = 4 tut + tw,up1 - 0.9 ms (or tactive = 4 tut + tw,up2 - 0.9 ms)

During the wake-up phase all analog modules are held powered-up, while during the sleep

phase most analog modules are powered down. Consequently, a wake-up time of at least tw,up1

(tw,up2) is needed to settle the analog modules so that reliable acceleration data are generated.

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4.3 Sensor data

4.3.1 Acceleration data

The width of acceleration data is 12 bits given in two´s complement representation. The 12 bits

for each axis are split into an MSB upper part (one byte containing bits 11 to 4) and an LSB

lower part (one byte containing bits 3 to 0 of acceleration and a (0x02, 0x04, 0x06) new_data

flag). Reading the acceleration data registers shall always start with the LSB part. In order to

ensure the integrity of the acceleration data, the content of an MSB register is locked by reading

the corresponding LSB register (shadowing procedure). When shadowing is enabled, the MSB

must always be read in order to remove the data lock. The shadowing procedure can be

disabled (enabled) by writing ´1´ (´0´) to the bit shadow_dis. With shadowing disabled, the

content of both MSB and LSB registers is updated by a new value immediately. Unused bits of

the LSB registers may have any value and should be ignored. The (0x02, 0x04, 0x06)

new_data flag of each LSB register is set if the data registers have been updated. The flag is

reset if either the corresponding MSB or LSB part is read.

Two different streams of acceleration data are available, unfiltered and filtered. The unfiltered

data is sampled with 2kHz. The sampling rate of the filtered data depends on the selected filter

bandwidth and is always twice the selected bandwidth (BW = ODR/2). Which kind of data is

stored in the acceleration data registers depends on bit (0x13) data_high_bw. If (0x13)

data_high_bw is ´0´ (´1´), then filtered (unfiltered) data is stored in the registers. Both data

streams are offset-compensated.

The bandwidth of filtered acceleration data is determined by setting the (0x10) bw bit as

followed:

Table 4: Bandwidth configuration

bw

Bandwidth

Update Time

tut

00xxx

*)

-

01000

7.81Hz

64ms

01001

15.63Hz

32ms

01010

31.25Hz

16ms

01011

62.5Hz

8ms

01100

125Hz

4ms

01101

250Hz

2ms

01110

500Hz

1ms

01111

1000Hz

0.5ms

1xxxx

*)

-

*) Note: Settings 00xxx result in a bandwidth of 7.81 Hz; settings 1xxxx result in a bandwidth of

1000 Hz. It is recommended to actively set an application specific and an appropriate bandwidth

and to use the range from ´01000b´ to ´01111b´ only in order to be compatible with future

products.

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The BMA255 supports four different acceleration measurement ranges. A measurement range

is selected by setting the (0x0F) range bits as follows:

Table 5: Range selection

Range

Acceleration

measurement

range

Resolution

0011

±2g

0.98mg/LSB

0101

±4g

1.95mg/LSB

1000

±8g

3.91mg/LSB

1100

±16g

7.81mg/LSB

others

reserved

-

4.3.2 Temperature sensor

The width of temperature data is 8 bits given in two´s complement representation. Temperature

values are available in the (0x08) temp register.

The slope of the temperature sensor is 0.5K/LSB, its center temperature is 23°C [(0x08) temp =

0x00].

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4.4 Self-test

This feature permits to check the sensor functionality by applying electrostatic forces to the

sensor core instead of external accelerations. By actually deflecting the seismic mass, the

entire signal path of the sensor can be tested. Activating the self-test results in a static offset of

the acceleration data; any external acceleration or gravitational force applied to the sensor

during active self-test will be observed in the output as a superposition of both acceleration and

self-test signal.

Before the self-test is enabled the g-range should be set to 4 g. The self-test is activated

individually for each axis by writing the proper value to the (0x32) self_test_axis bits (´01b´ for x-

axis, ´10b´ for y-axis, ´11b´ for z-axis, ´00b´ to deactivate self-test). It is possible to control the

direction of the deflection through bit (0x32) self_test_sign. The excitation occurs in negative

(positive) direction if (0x32) self_test_sign = ´0b´ (´1b´). After the self-test is enabled, the user

should wait 50ms before interpreting the acceleration data.

In order to ensure a proper interpretation of the self-test signal it is recommended to perform the

self-test for both (positive and negative) directions and then to calculate the difference of the

resulting acceleration values. Table 6 shows the minimum differences for each axis. The

actually measured signal differences can be significantly larger.

Table 6: Self-test difference values

x-axis signal

y-axis signal

z-axis signal

resulting minimum

difference signal

800 mg

400 mg

It is recommended to perform a reset of the device after a self-test has been performed. If the

reset cannot be performed, the following sequence must be kept to prevent unwanted interrupt

generation: disable interrupts, change parameters of interrupts, wait for at least 50ms, enable

desired interrupts.

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4.5 Offset compensation

Offsets in measured signals can have several causes but they are always unwanted and

disturbing in many cases. Therefore, the BMA255 offers an advanced set of four digital offset

compensation methods which are closely matched to each other. These are slow, fast, and

manual compensation as well as inline calibration.

The compensation is performed with unfiltered data, and is then applied to both, unfiltered and

filtered data. If necessary the result of this computation is saturated to prevent any overflow

errors (the smallest or biggest possible value is set, depending on the sign). However, the

registers used to read and write compensation values have a width of 8 bits.

An overview of the offset compensation principle is given in figure 5:

1g

7.8mg

15.6mg

31.2mg

62.5mg

125mg

250mg

500mg

Sign

3.9mg

1.9mg

0.97mg

1g

7.8mg

15.6mg

31.2mg

62.5mg

125mg

250mg

500mg

Sign

3.9mg

1.9mg

2g

1g

7.8mg

15.6mg

31.2mg

62.5mg

125mg

250mg

500mg

Sign

3.9mg

2g

4g

Sign

1g

7.8mg

15.6mg

31.2mg

62.5mg

125mg

250mg

500mg

8g

2g

4g

MSB

LSB

-

+-2g

+-4g

+-8g

+-16g

Sign

MSB

LSB 7.8mg

15.6mg

31.2mg

62.5mg

125mg

250mg

500mg

Read/

Write

12 bit acceleration data rangeI2C/SPI/NVM mapping

Figure 5: Principle of offset compensation

BMA255

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The public offset compensation registers (0x38) offset_x, (0x39) offset_y, (0x3A) offset_z are

images of the corresponding registers in the NVM. With each image update (see section 4.6

Non-volatile memory for details) the contents of the NVM registers are written to the public

registers. The public registers can be over-written by the user at any time. After changing the

contents of the public registers by either an image update or manually, all 8bit values are

extended to 12bit values for internal computation. In the opposite direction, if an internally

computed value changes it is converted to an 8bit value and stored in the public register.

Depending on the selected g-range the conversion from 12bit to 8bit values can result in a loss

of accuracy of one to several LSB. This is shown in figure 5.

In case an internally computed compensation value is too small or too large to fit into the

corresponding register, it is saturated in order to prevent an overflow error.

By writing ´1´ to the (0x36) offset_reset bit, all offset compensation registers are reset to zero.

BMA255

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4.5.1 Slow compensation

Slow compensation is based on a 1st order high-pass filter, which continuously drives the

average value of the output data stream of each axis to zero. The bandwidth of the high-pass

filter is configured with bit (0x37) cut_off according to Table 7.

Table 7: Compensation period settings

(0x37)

cut_off

high-pass filter

bandwidth

Example

bw = 500 Hz

0b

1b

*bw: please insert selected decimal data bandwidth value [Hz] from table 4

The slow compensation can be enabled (disabled) for each axis independently by setting the

bits (0x36) hp_x_en, hp_y_en, hp_z_en to ´1´ (´0´), respectively.

Slow compensation should not be used in combination with low-power mode. In low-power

mode the conditions (availability of necessary data) for proper function of slow compensation

are not fulfilled.

4.5.2 Fast compensation

Fast compensation is a one-shot process by which the compensation value is set in such a way

that when added to the raw acceleration, the resulting acceleration value of each axis

approaches the target value. This is best suited for “end-of-line trimming” with the customer’s

device positioned in a well-defined orientation. For fast compensation the g-range has to be

switched to 2g.

The algorithm in detail: An average of 16 consecutive acceleration values is computed and the

difference between target value and computed value is written to (0x38, 0x39, 0x3A)

offset_filt_x/y/z. The public registers (0x38, 0x39, 0x3A) offset_filt_x/y/z are updated with the

contents of the internal registers (using saturation if necessary) and can be read by the user.

Fast compensation is triggered for each axis individually by setting the (0x36) cal_trigger bits as

shown in Table 8:

Table 8: Fast compensation axis selection

(0x36)

cal_trigger

Selected Axis

00b

none

01b

x

10b

y

11b

z

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Register (0x36) cal_trigger is a write-only register. Once triggered, the status of the fast

correction process is reflected in the status bit (0x36) cal_rdy. Bit (0x36) cal_rdy is ‘0’ while the

correction is in progress. Otherwise it is ‘1’. Bit (0x36) cal_rdy is ´0´ when (0x36) cal_trigger is

not ´00´.

For the fast offset compensation, the compensation target can be chosen by setting the bits

(0x37) offset_target_x, (0x37) offset_target_y, and (0x37) offset_target_z according to Table 9:

Table 9: Offset target settings

(0x37)

offset_target_x/y/z

Target value

00b

0g

01b

+1g

10b

-1g

11b

0g

Fast compensation should not be used in combination with any of the low-power modes. In low-

power mode the conditions (availability of necessary data) for proper function of fast

compensation are not fulfilled.

4.5.3 Manual compensation

The contents of the public compensation registers (0x38, 0x39, 0x3A) offset_filt_x/y/z can be

set manually via the digital interface. It is recommended to write into these registers directly

after a new data interrupt has occurred in order not to disturb running offset computations.

Writing to the offset compensation registers is not allowed while the fast compensation

procedure is running.

4.5.4 Inline calibration

For certain applications, it is often desirable to calibrate the offset once and to store the

compensation values permanently. This can be achieved by using one of the aforementioned

offset compensation methods to determine the proper compensation values and then storing

these values permanently in the NVM. See section 4.6 Non-volatile memory for details of the

storing procedure.

Each time the device is reset, the compensation values are loaded from the non-volatile

memory into the image registers and used for offset compensation until they are possibly

overwritten using one of the other compensation methods.

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4.6 Non-volatile memory

The entire memory of the BMA255 consists of three different kinds of registers: hard-wired,

volatile, and non-volatile. Part of it can be both read and written by the user. Access to non-

volatile memory is only possible through (volatile) image registers.

Altogether, there are eight registers (octets) with NVM backup which are accessible by the user.

The addresses of the image registers range from 0x38 to 0x3C. While the addresses up to

0x3A are used for offset compensation (see 4.4 Offset Compensation), addresses 0x3B and

0x3C are general purpose registers not linked to any sensor-specific functionality.

The content of the NVM is loaded to the image registers after a reset (either POR or softreset)

or after a user request which is performed by writing ´1´ to the write-only bit (0x33) nvm_load.

As long as the image update is in progress, bit (0x33) nvm_rdy is ´0´, otherwise it is ´1´.

The image registers can be read and written like any other register.

Writing to the NVM is a three-step procedure:

1. Write the new contents to the image registers.

2. Write ´1´ to bit (0x33) nvm_prog_mode in order to unlock the NVM.

3. Write ´1´ to bit (0x33) nvm_prog_trig and keep ´1´ in bit (0x33) nvm_prog_mode in order

to trigger the write process.

Writing to the NVM always renews the entire NVM contents. It is possible to check the write

status by reading bit (0x33) nvm_rdy. While (0x33) nvm_rdy = ´0´, the write process is still in

progress; if (0x33) nvm_rdy = ´1´, then writing is completed. As long as the write process is

ongoing, no change of power mode and image registers is allowed. Also, the NVM write cycle

must not be initiated while image registers are updated, in low-power mode, and in suspend

mode.

Please note that the number of permitted NVM write-cycles is limited as specified in Table 1.

The number of remaining write-cycles can be obtained by reading bits (0x33) nvm_remain.

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4.7 Interrupt controller

The BMA255 is equipped with eight programmable interrupt engines. Each interrupt can be

independently enabled and configured. If the trigger condition of an enabled interrupt is fulfilled,

the corresponding status bit is set to ´1´ and the selected interrupt pin is activated. The BMA255

provides two interrupt pins, INT1 and INT2; interrupts can be freely mapped to any of these

pins. The state of a specific interrupt pin is derived from a logic ´or´ combination of all interrupts

mapped to it.

The interrupt status registers are updated when a new data word is written into the acceleration

data registers. If an interrupt is disabled, all active status bits associated with it are immediately

reset.

4.7.1 General features

An interrupt is cleared depending on the selected interrupt mode, which is common to all

interrupts. There are three different interrupt modes: non-latched, latched, and temporary. The

mode is selected by the (0x21) latch_int bits according to Table 10.

Table 10: Interrupt mode selection

(0x21)

latch_int

Interrupt mode

0000b

non-latched

0001b

temporary, 250ms

0010b

temporary, 500ms

0011b

temporary, 1s

0100b

temporary, 2s

0101b

temporary, 4s

0110b

temporary, 8s

0111b

latched

1000b

non-latched

1001b

temporary, 250µs

1010b

temporary, 500µs

1011b

temporary, 1ms

1100b

temporary, 12.5ms

1101b

temporary, 25ms

1110b

temporary, 50ms

1111b

latched

An interrupt is generated if its activation condition is met. It can not be cleared as long as the

activation condition is fulfilled. In the non-latched mode the interrupt status bit and the selected

pin (the contribution to the ´or´ condition for INT1 and/or INT2) are cleared as soon as the

activation condition is no more valid. Exceptions to this behavior are the new data, orientation,

and flat interrupts, which are automatically reset after a fixed time.

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In latched mode an asserted interrupt status and the selected pin are cleared by writing ´1´ to

bit (0x21) reset_int. If the activation condition still holds when it is cleared, the interrupt status is

asserted again with the next change of the acceleration registers.

In the temporary mode an asserted interrupt and selected pin are cleared after a defined period

of time. The behaviour of the different interrupt modes is shown graphically in figure 6. The

timings in this mode are subject to the same tolerances as the bandwidths (see Table 1).

internal signal from

interrupt engine

interrupt output

non-latched

temporary

latched

latch period

Figure 6: Interrupt modes

Several interrupt engines can use either unfiltered or filtered acceleration data as their input. For

these interrupts, the source can be selected with the bits in register (0x1E). These are (0x1E)

int_src_data, (0x1E) int_src_tap, (0x1E) int_src_slo_no_mot, (0x1E) int_src_slope, (0x1E)

int_src_high, and (0x1E) int_src_low. Setting the respective bits to ´0´ (´1´) selects filtered

(unfiltered) data as input. The orientation recognition and flat detection interrupt always use

filtered input data.

It is strongly recommended to set interrupt parameters prior to enabling the interrupt. Changing

parameters of an already enabled interrupt may cause unwanted interrupt generation and

generation of a false interrupt history. A safe way to change parameters of an enabled interrupt

is to keep the following sequence: disable the desired interrupt, change parameters, wait for at

least 10ms, and then re-enable the desired interrupt.

4.7.2 Mapping to physical interrupt pins (inttype to INT Pin#)

Registers (0x19) to (0x1B) are dedicated to mapping of interrupts to the interrupt pins “INT1” or

“INT2”. Setting (0x19) int1_”inttype” to ´1´ (´0´) maps (unmaps) “inttype” to pin “INT1”.

Correspondingly setting (0x1B) int2_”inttype” to ´1´ (´0´) maps (unmaps) “inttype” to pin “INT2”.

Note: “inttype” to be replaced with the precise notation, given in the memory map in chapter 6.

Example: For flat interrupt (int1_flat): Setting (0x19) int1_flat to ´1´ maps int1_flat to pin “INT1”.

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4.7.3 Electrical behaviour (INT pin# to open-drive or push-pull)

Both interrupt pins can be configured to show the desired electrical behaviour. The ´active´ level

of each interrupt pin is determined by the (0x20) int1_lvl and (0x20) int2_lvl bits.

If (0x20) int1_lvl = ´1´ (´0´) / (0x20) int2_lvl = ´1´ (´0´), then pin “INT1” / pin “INT2” is active ´1´

(´0´). The characteristic of the output driver of the interrupt pins may be configured with bits

(0x20) int1_od and (0x20) int2_od. By setting bits (0x20) int1_od / (0x20) int2_od to ´1´, the

output driver shows open-drive characteristic, by setting the configuration bits to ´0´, the output

driver shows push-pull characteristic. When open-drive characteristic is selected in the design,

external pull-up or pull-down resistor should be applied according the int_lvl configuration.

4.7.4 New data interrupt

This interrupt serves for synchronous reading of acceleration data. It is generated after storing a

new value of z-axis acceleration data in the data register. The interrupt is cleared automatically

when the next data acquisition cycle starts. The interrupt status is ´0´ for at least 50µs.

The interrupt mode of the new data interrupt is fixed to non-latched.

It is enabled (disabled) by writing ´1´ (´0´) to bit (0x17) data_en. The interrupt status is stored in

bit (0x0A) data_int.

Due to the settling time of the filter, the first interrupt after wake-up from suspend or standby

mode will take longer than the update time.

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slope_th

INT

slope

acceleration

acc(t0)

acc(t0−1/(2*bw))

slope(t0)=acc(t0)−acc(t0−1/(2*bw))

time

slope_dur

4.7.5 Slope / any-motion detection

Slope / any-motion detection uses the slope between successive acceleration signals to detect

changes in motion. An interrupt is generated when the slope (absolute value of acceleration

difference) exceeds a preset threshold. It is cleared as soon as the slope falls below the

threshold. The principle is made clear in figure 7.

Figure 7: Principle of any-motion detection

The threshold is defined through register (0x28) slope_th. In terms of scaling 1 LSB of (0x28)

slope_th corresponds to 3.91 mg in 2g-range (7.81 mg in 4g-range, 15.6 mg in 8g-range and

31.3 mg in 16g-range). Therefore the maximum value is 996 mg in 2g-range (1.99g in 4g-

range, 3.98g in 8g-range and 7.97g in 16g-range).

The time difference between the successive acceleration signals depends on the selected

bandwidth and equates to 1/(2*bandwidth) (t=1/(2*bw)). In order to suppress false triggers, the

interrupt is only generated (cleared) if a certain number N of consecutive slope data points is

larger (smaller) than the slope threshold given by (0x28) slope_th. This number is set by the

(0x27) slope_dur bits. It is N = (0x27) slope_dur + 1 for (0x27).

Example: (0x27) slope_dur = 00b, …, 11b = 1decimal, …, 4decimal.

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4.7.5.1 Enabling (disabling) for each axis

Any-motion detection can be enabled (disabled) for each axis separately by writing ´1´ (´0´) to

bits (0x16) slope_en_x, (0x16) slope_en_y, (0x16) slope_en_z. The criteria for any-motion

detection are fulfilled and the slope interrupt is generated if the slope of any of the enabled axes

exceeds the threshold (0x28) slope_th for [(0x27) slope_dur +1] consecutive times. As soon as

the slopes of all enabled axes fall or stay below this threshold for [(0x27) slope_dur +1]

consecutive times the interrupt is cleared unless interrupt signal is latched.

4.7.5.2 Axis and sign information of slope / any motion interrupt

The interrupt status is stored in bit (0x09) slope_int. The any-motion interrupt supplies additional

information about the detected slope. The axis which triggered the interrupt is given by that one

of bits (0x0B) slope_first_x, (0x0B) slope_first_y, (0x0B) slope_first_z that contains a value of

´1´. The sign of the triggering slope is held in bit (0x0B) slope_sign until the interrupt is

retriggered. If (0x0B) slope_sign = ´0´ (´1´), the sign is positive (negative).

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4.7.6 Tap sensing

Tap sensing has a functional similarity with a common laptop touch-pad or clicking keys of a

computer mouse. A tap event is detected if a pre-defined slope of the acceleration of at least

one axis is exceeded. Two different tap events are distinguished: A ‘single tap’ is a single event

within a certain time, followed by a certain quiet time. A ‘double tap’ consists of a first such

event followed by a second event within a defined time frame.

Single tap interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) s_tap_en. Double tap

interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) d_tap_en.

While temporary latching is used do not simultaneously enable single tap interrupt and double

tap interrupt.

The status of the single tap interrupt is stored in bit (0x09) s_tap_int, the status of the double

tap interrupt is stored in bit (0x09) d_tap_int.

The slope threshold for detecting a tap event is set by bits (0x2B) tap_th. The meaning of

(0x2B) tap_th depends on the range setting. 1 LSB of (0x2B) tap_th corresponds to a slope of

62.5mg in 2g-range, 125mg in 4g-range, 250mg in 8g-range, and 500mg in 16g-range.

In figure 8 the meaning of the different timing parameters is visualized:

tap_shock tap_quiet tap_dur

tap_shock tap_quiet

time

12.5 ms

single tap detection

double tap detection

slope

time

12.5 ms

time

1st tap 2nd tap

tap_th

Figure 8: Timing of tap detection

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The parameters (0x2A) tap_shock and (0x2A) tap_quiet apply to both single tap and double tap

detection, while (0x2A) tap_dur applies to double tap detection only. Within the duration of

(0x2A) tap_shock any slope exceeding (0x2B) tap_th after the first event is ignored. Contrary to

this, within the duration of (0x2A) tap_quiet no slope exceeding (0x2B) tap_th must occur,

otherwise the first event will be cancelled.

4.7.6.1 Single tap detection

A single tap is detected and the single tap interrupt is generated after the combined durations of

(0x2A) tap_shock and (0x2A) tap_quiet, if the corresponding slope conditions are fulfilled. The

interrupt is cleared after a delay of 12.5 ms.

Do not map single-tap to any INT pin if you do not want to use it.

4.7.6.2 Double tap detection

A double tap interrupt is generated if an event fulfilling the conditions for a single tap occurs

within the set duration in (0x2A) tap_dur after the completion of the first tap event. The interrupt

is automatically cleared after a delay of 12.5 ms.

4.7.6.3 Selecting the timing of tap detection

For each of parameters (0x2A) tap_shock and (0x2A) tap_quiet two values are selectable. By

writing ´0´ (´1´) to bit (0x2A) tap_shock the duration of (0x2A) tap_shock is set to 50 ms (75

ms). By writing ´0´ (´1´) to bit (0x2A) tap_quiet the duration of (0x2A) tap_quiet is set to 30 ms

(20 ms).

The length of (0x2A) tap_dur can be selected by setting the (0x2A) tap_dur bits according to

Table 11:

Table 11: Selection of tap_dur

(0x2A)

tap_dur

length of tap_dur

000b

50 ms

001b

100 ms

010b

150 ms

011b

200 ms

100b

250 ms

101b

375 ms

110b

500 ms

111b

700 ms

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4.7.6.4 Axis and sign information of tap sensing

The sign of the slope of the first tap which triggered the interrupt is stored in bit (0x0B) tap_sign

(´0´ means positive sign, ´1´ means negative sign). The value of this bit persists after clearing

the interrupt.

The axis which triggered the interrupt is indicated by bits (0x0B) tap_first_x, (0x0B) tap_first_y,

and (0x0B) tap_first_z.

The bit corresponding to the triggering axis contains a ´1´ while the other bits hold a ´0´. These

bits are cleared together with clearing the interrupt status.

4.7.6.5 Tap sensing in low power mode

In low-power mode, a limited number of samples is processed after wake-up to decide whether

an interrupt condition is fulfilled. The number of samples is selected by bits (0x2B) tap_samp

according to Table 12.

Table 12: Meaning of (0x2B) tap_samp

(0x2B)

tap_samp

Number of Samples

00b

2

01b

4

10b

8

11b

16

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4.7.7 Orientation recognition

The orientation recognition feature informs on an orientation change of the sensor with respect

to the gravitational field vector ‘g’. The measured acceleration vector components with respect

to the gravitational field are defined as shown in figure 9.

Figure 9: Definition of vector components

Therefore, the magnitudes of the acceleration vectors are calculated as follows:

acc_x = 1g x sin x cos

acc_y = −1g x sin x sin

acc_z = 1g x cos

acc_y/acc_x = −tan

Depending on the magnitudes of the acceleration vectors the orientation of the device in the

space is determined and stored in the three (0x0C) orient bits. These bits may not be reset in

the sleep phase of low-power mode. There are three orientation calculation modes with different

thresholds for switching between different orientations: symmetrical, high-asymmetrical, and

low-asymmetrical. The mode is selected by setting the (0x2C) orient_mode bits as given in

Table 13.

Table 13: Orientation mode settings

(0x2C)

orient_mode

Orientation Mode

00b

symmetrical

01b

high-asymmetrical

10b

low-asymmetrical

11b

symmetrical

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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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Figure 10 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

0.5

1

1.5

2

0 45 90 135 180 225 270 315 360

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

0.5

1

1.5

2

0 45 90 135 180 225 270 315 360



acc_y/acc_x

acc_x/sin(theta)

acc_y/sin(theta)

portrait upright landscape left portrait upside

down

landscape right portrait upright

Figure 10: 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

6.

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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

no blocking

01b

theta blocking

or

acceleration in any axis > 1.5g

10b

theta blocking

or

acceleration slope in any axis > 0.2 g

or

acceleration in any axis > 1.5g

11b

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:

.

8

_

tan thetablocking





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

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changes state. The BMA255 can be configured to trigger orientation interrupts only when the

device position changes in the x-y-plane while orientation changes with respect to the z-axis are

ignored. A change of the orientation of the z-axis, and hence a state change of bit (0x0C)

orient<2> is ignored (considered) when bit (0x2D) orient_ud_en is set to ‘0’ (‘1’).

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4.7.8 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 flat angle  is adjustable by (0x2E) flat_theta from 0° to 44.8°. The flat angle can be set

according to following formula:













 flat_theta

8

1

atan

A hysteresis of the flat detection can be enabled by (0x2F) flat_hy bits. In this case the flat

position is set if the angle drops below following threshold:























 16

_

1024

_

1flat_theta

8

1

atan

,hyflathyflat

llhyst

The flat position is reset if the angle exceeds the following threshold:























 16

_

1024

_

1flat_theta

8

1

atan

,hyflathyflat

ulhyst

The flat interrupt is enabled (disabled) by writing ´1´ (´0´) to bit (0x16) flat_en. 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 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. A flat interrupt

may be also generated if the flat interrupt is enabled. The actual status of the interrupt is stored

in the (0x09) flat_int bit. The flat orientation of the sensor can always be determined from

reading the (0x0C) flat bit after interrupt generation. If unlatched interrupt mode is used, the

(0x09) flat_int value and hence the interrupt is automatically cleared after one sample period. If

temporary or latched interrupt mode is used, the (0x09) flat_int value is kept fixed until the latch

time expires or the interrupt is reset.

The meaning of the (0x2F) flat_hold_time bits can be seen from Table 18.

Table 18: Meaning of flat_hold_time

(0x2F)

flat_hold_time

Time

00b

0

01b

512 ms

10b

1024 ms

11b

2048 ms

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4.7.9 Low-g interrupt

This interrupt is based on the comparison of acceleration data against a low-g threshold, which

is most useful for free-fall detection.

The interrupt is enabled (disabled) by writing ´1´ (´0´) to the (0x17) low_en bit. There are two

modes available, ‘single’ mode and ‘sum’ mode. In ‘single’ mode, the acceleration of each axis

is compared with the threshold; in ‘sum’ mode, the sum of absolute values of all accelerations

contents of the (0x24) low_mode bit: ´0´ means ‘single’ mode, ´1´ means ‘sum’ mode.

The low-g threshold is set through the (0x23) low_th register. 1 LSB of (0x23) low_th always

corresponds to an acceleration of 7.81 mg (i.e. increment is independent from g-range setting).

A hysteresis can be selected by setting the (0x24) low_hy bits. 1 LSB of (0x24) low_hy always

corresponds to an acceleration difference of 125 mg in any g-range (as well, increment is

independent from g-range setting).

The low-g interrupt is generated if the absolute values of the acceleration of all axes (´and´

relation, in case of single mode) or their sum (in case of sum mode) are lower than the

threshold for at least the time defined by the (0x22) low_dur register. The interrupt is reset if the

absolute value of the acceleration of at least one axis (´or´ relation, in case of single mode) or

the sum of absolute values (in case of sum mode) is higher than the threshold plus the

hysteresis for at least one data acquisition. In bit (0x09) low_int the interrupt status is stored.

The relation between the content of (0x22) low_dur and the actual delay of the interrupt

generation is: delay [ms] = [(0x22) low_dur + 1] • 2 ms. Therefore, possible delay times range

from 2 ms to 512 ms.

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4.7.10 High-g interrupt

This interrupt is based on the comparison of acceleration data against a high-g threshold for the

detection of shock or other high-acceleration events.

The high-g interrupt is enabled (disabled) per axis by writing ´1´ (´0´) to bits (0x17) high_en_x,

(0x17) high_en_y, and (0x17) high_en_z, respectively. The high-g threshold is set through the

(0x26) high_th register. The meaning of an LSB of (0x26) high_th depends on the selected g-

range: it corresponds to 7.81 mg in 2g-range, 15.63 mg in 4g-range, 31.25 mg in 8g-range, and

62.5 mg in 16g-range (i.e. increment depends from g-range setting).

A hysteresis can be selected by setting the (0x24) high_hy bits. Analogously to (0x26) high_th,

the meaning of an LSB of (0x24) high_hy is g-range dependent: It corresponds to an

acceleration difference of 125 mg in 2g-range, 250 mg in 4g-range, 500 mg in 8g-range, and

1000mg in 16g-range (as well, increment depends from g-range setting).

The high-g interrupt is generated if the absolute value of the acceleration of at least one of the

enabled axes (´or´ relation) is higher than the threshold for at least the time defined by the

(0x25) high_dur register. The interrupt is reset if the absolute value of the acceleration of all

enabled axes (´and´ relation) is lower than the threshold minus the hysteresis for at least the

time defined by the (0x25) high_dur register. In bit (0x09) high_int the interrupt status is stored.

The relation between the content of (0x25) high_dur and the actual delay of the interrupt

generation is delay [ms] = [(0x22) low_dur + 1] • 2 ms. Therefore, possible delay times range

from 2 ms to 512 ms. The interrupt will be cleared immediately once acceleration is lower than

threshold.

4.7.10.1 Axis and sign information of high-g interrupt

The axis which triggered the interrupt is indicated by bits (0x0C) high_first_x, (0x0C)

high_first_y, and (0x0C) high_first_z. The bit corresponding to the triggering axis contains a ´1´

while the other bits hold a ´0´. These bits are cleared together with clearing the interrupt status.

The sign of the triggering acceleration is stored in bit (0x0C) high_sign. If (0x0C) high_sign = ´0´

(´1´), the sign is positive (negative).

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4.7.11 No-motion / slow motion detection

The slow-motion/no-motion interrupt engine can be configured in two modes.

In slow-motion mode an interrupt is triggered when the measured slope of at least one enabled

axis exceeds the programmable slope threshold for a programmable number of samples.

Hence the engine behaves similar to the any-motion interrupt, but with a different set of

parameters. In order to suppress false triggers, the interrupt is only generated (cleared) if a

certain number N of consecutive slope data points is larger (smaller) than the slope threshold

given by (0x27) slo_no_mot_dur<1:0>. The number is N = (0x27) slo_no_mot_dur<1:0> + 1.

In no-motion mode an interrupt is generated if the slope on all selected axes remains smaller

than a programmable threshold for a programmable delay time. Figure 11 shows the timing

diagram for the no-motion interrupt. The scaling of the threshold value is identical to that of the

slow-motion interrupt. However, in no-motion mode register (0x27) slo_no_mot_dur defines the

delay time before the no-motion interrupt is triggered. Table 19 lists the delay times adjustable

with register (0x27) slo_no_mot_dur. The timer tick period is 1 second. Hence using short delay

times can result in considerable timing uncertainty.

If bit (0x18) slo_no_mot_sel is set to ‘1’ (‘0’) the no-motion/slow-motion interrupt engine is

configured in the no-motion (slow-motion) mode. Common to both modes, the engine monitors

the slopes of the axes that have been enabled with bits (0x18) slo_no_mot_en_x, (0x18)

slo_no_mot_en_y, and (0x18) slo_no_mot_en_z for the x-axis, y-axis and z-axis, respectively.

The measured slope values are continuously compared against the threshold value defined in

register (0x29) slo_no_mot_th. The scaling is such that 1 LSB of (0x29) slo_no_mot_th

corresponds to 3.91 mg in 2g-range (7.81 mg in 4g-range, 15.6 mg in 8g-range and 31.3 mg in

16g-range). Therefore the maximum value is 996 mg in 2g-range (1.99g in 4g-range, 3.98g in

8g-range and 7.97g in 16g-range). The time difference between the successive acceleration

samples depends on the selected bandwidth and equates to 1/(2 * bw).

Table 19: No-motion time-out periods

(0x27)

slo_no_mot_dur

Delay

time

(0x27)

slo_no_mot_dur

Delay

time

(0x27)

slo_no_mot_dur

Delay

Time

0

1 s

16

40 s

32

88 s

1

2 s

17

48 s

33

96 s

2

3 s

18

56 s

34

104 s

...

19

64 s.

...

14

15 s

20

72 s

62

328 s

15

16 s

21

80 s

63

336 s

Note: slo_no_mot_dur values 22 to 31 are not specified

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acceleration

slo_no_mot_th

-slo_no_mot_th

slope

time

axis x, y, or z

slo_no_mot_dur

timer

INT

slope(t0+Δt)= acc(t0+Δt) - acc(t0)

acc(t0+Δt)

acc(t0)

Figure 11: Timing of No-motion interrupt

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4.8 Softreset

A softreset causes all user configuration settings to be overwritten with their default value and

the sensor to enter normal mode.

A softreset is initiated by means of writing value 0xB6 to register (0x14) softreset. Subsequently

a waiting time of tw,up1 (max.) is required prior to accessing any configuration registers.

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5. FIFO Operation

5.1 FIFO Operating Modes

The BMA255 features an integrated FIFO memory capable of storing up to 32 frames.

Conceptually each frame consists of three 16 bit words corresponding to the x, y and z- axis,

which are sampled at the same point in time. At the core of the FIFO is a buffer memory, which

can be configured to operate in the following modes:

 FIFO Mode: In FIFO mode the acceleration data of the selected axes are stored in the

buffer memory. If enabled, a watermark interrupt is triggered when the buffer has filled

up to a configurable level. The buffer will be continuously filled until the fill level reaches

32 frames. When it is full the data collection is stopped, and all additional samples are

ignored. Once the buffer is full, a FIFO-full interrupt is generated if it has been enabled.

 STREAM Mode: In STREAM mode the acceleration data of the selected axes are

stored in the buffer until it is full. The buffer has a depth of 31 frames. When the buffer is

full the data collection continues and oldest entry is discarded. If enabled, a watermark

interrupt is triggered when the buffer is filled to a configurable level. Once the buffer is

full, a FIFO-full interrupt is generated if it has been enabled.

 BYPASS Mode: In bypass mode, only the current sensor data can be read out from the

FIFO address. Essentially, the FIFO behaves like the STREAM mode with a depth of 1.

Compared to reading the data from the normal data registers, the advantage to the user

is that the packages X, Y, Z are from the same timestamp, while the data registers are

updated sequentially and hence mixing of data from different axes can occur.

The primary FIFO operating mode is selected with register (0x3E) fifo_mode according to ‘00b’

for BYPASS mode, ‘01b’ for FIFO mode, and ‘10b’ for STREAM mode. Writing to register

(0x3E) clears the buffer content and resets the FIFO-full and watermark interrupts. When

reading register (0x3E) fifo_mode always contains the current operating mode.

BMA255

Data sheet

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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.

5.2 FIFO Data Readout

The FIFO stores the data that are also available at the acceleration read-out registers (0x02) to

(0x07). Thus, all configuration settings apply to the FIFO data as well as the acceleration data

readout registers. The FIFO read out is possible through register (0x3F). The readout can be

performed using burst mode since the read address counter is no longer incremented, when it

has reached address (0x3F). This implies that the trapping also occurs when the burst read

access starts below address (0x3F). A single burst can read out one or more frames at a time.

Register (0x3E) fifo_data_select controls the acceleration data of which axes are stored in the

FIFO. Possible settings for register (0x3E) fifo_data_select are ‘00b’ for x, y- and z-axis, ‘01b’

for x-axis only, ‘10b’ for y-axis, ‘11b’ for z-axis only. The depth of the FIFO is independent of

whether all or a single axis have been selected. Writing to register (0x3E) clears the buffer

content and resets the FIFO-full and watermark interrupts.

If all axes are enabled, the format of the data read-out from register (0x3F) is as follows:

If only one axis is enabled, the format of the data read-out from register (0x3F) is as follows

(example shown: y-axis only, other axes are equivalent).

If a frame is not completely read due to an incomplete read operation, the remaining part of the

frame is discarded. In this case the FIFO aligns to the next frame during the next read

operation. In order for the discarding mechanism to operate correctly, there must be a delay of

at least 1.5 us between the last data bit of the partially read frame and the first address bit of the

next FIFO read access. Otherwise frames must not be read out partially.

If the FIFO is read beyond the FIFO fill level zeroes (0) will be read. If the FIFO is read beyond

the FIFO fill level the read or burst read access time must not exceed the sampling time tSAMPLE.

Otherwise frames may be lost.

5.3 FIFO Frame Counter and Overrun Flag

Register (0x0E) fifo_frame_counter reflects the current fill level of the buffer. If additional frames

are written to the buffer although the FIFO is full, the (0x0E) fifo_overrun bit is set to ‘1’. The

FIFO buffer is cleared, the FIFO fill level indicated in register (0x0E) fifo_frame_counter and the

(0x0E) fifo_overrun bit are both set to ‘0’ each time one a write access to one of the FIFO

configuration registers (0x3E) or (0x30) occurs. The (0x0E) fifo_overrun bit is not reset when

the FIFO fill level (0x0E) fifo_frame_counter has decremented to ‘0’ due to reading from register

(0x3F).

…

Frame 1

Y LSB

Y MSB

Y LSB

Y MSB

Frame 2

Frame 1

X LSB

X MSB

Y LSB

Y MSB

Z LSB

Z MSB

…

BMA255

Data sheet

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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.

5.4 FIFO Interrupts

The FIFO controller can generate two different interrupt events, a FIFO-full and a watermark

event. The FIFO-full and watermark interrupts are functional in all FIFO operating modes. The

watermark interrupt is asserted when the fill level in the buffer has reached the frame count

defined by register (0x30) fifo_water_mark_trigger_retain. In order to enable (disable) the

watermark interrupt, the (0x17) int_fwm_en bit must be set to ‘1’ (‘0’). To map the watermark

interrupt signal to INT1 pin (INT2 pin), (0x1A) int1_fwm ((0x1A) int2_fwm) bit must be set to ‘1’.

The status of the watermark interrupt may be read back through the (0x0A) fifo_wm_int bit.

Writing to register (0x30) fifo_water_mark_trigger_retain clears the FIFO buffer.

The FIFO-full interrupt is triggered when the buffer has been completely filled. In FIFO mode

this occurs 32, in STREAM mode 31 samples, and in BYPASS mode 1 sample after the buffer

has been cleared. In order to enable the FIFO-full interrupt, bit (0x17) int_ffull_en as well as one

or both of bits (0x1A) int1_fful or (0x1A) int2_fful must also be set to ‘1’. The status of the FIFO-

full interrupt may be read back through bit (0x0A) fifo_full_int.

BMA255

Data sheet

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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.

6. Register description

6.1 General remarks

The entire communication with the device is performed by reading from and writing to registers.

Registers have a width of 8 bits; they are mapped to a common space of 64 addresses from

(0x00) up to (0x3F). Within the used range there are several registers which are either

completely or partially marked as ‘reserved’. Any reserved bit is ignored when it is written and

no specific value is guaranteed when read. It is recommended not to use registers at all which

are completely marked as ‘reserved’. Furthermore it is recommended to mask out (logical and

with zero) reserved bits of registers which are partially marked as reserved.

Registers with addresses from (0x00) up to (0x0E) are read-only. Any attempt to write to these

registers is ignored. There are bits within some registers that trigger internal sequences. These

bits are configured for write-only access, e. g. (0x21) reset_int or the entire (0x14) softreset

register, and read as value ´0´.

BMA255

Data sheet

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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.

6.2 Register map

Register Address bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 Access Default

0x3F ro 0x00

0x3E w/r 0x00

0x3D w/r 0xFF

0x3C w/r 0x00

0x3B w/r 0x00

0x3A w/r 0x00

0x39 w/r 0x00

0x38 w/r 0x00

0x37 cut_off w/r 0x00

0x36 offset_reset cal_rdy hp_z_en hp_y_en hp_x_en w/r 0x10

0x35 w/r 0x00

0x34 i2c_wdt_en i2c_wdt_sel spi3 w/r 0x00

0x33 nvm_load nvm_rdy nvm_prog_trig nvm_prog_mode w/r 0xF0

0x32 self_test_sign w/r 0x00

0x31 w/r 0xFF

0x30 w/r 0x00

0x2F w/r 0x11

0x2E w/r 0x08

0x2D orient_ud_en w/r 0x48

0x2C w/r 0x18

0x2B w/r 0x0A

0x2A

tap_quiet tap_shock w/r 0x04

0x29 w/r 0x14

0x28 w/r 0x14

0x27 w/r 0x00

0x26 w/r 0xC0

0x25 w/r 0x0F

0x24 low_mode w/r 0x81

0x23 w/r 0x30

0x22 w/r 0x09

0x21 reset_int w/r 0x00

0x20 int2_od int2_lvl int1_od int1_lvl w/r 0x05

0x1F w/r 0xFF

0x1E int_src_data int_src_tap int_src_slo_no_mot int_src_slope int_src_high int_src_low w/r 0x00

0x1D w/r 0xFF

0x1C w/r 0xFF

0x1B int2_flat int2_orient int2_s_tap int2_d_tap int2_slo_no_mot int2_slope int2_high int2_low w/r 0x00

0x1A int2_data int2_fwm int2_ffull int1_ffull int1_fwm int1_data w/r 0x00

0x19 int1_flat int1_orient int1_s_tap int1_d_tap int1_slo_no_mot int1_slope int1_high int1_low w/r 0x00

0x18 slo_no_mot_sel slo_no_mot_en_z slo_no_mot_en_y slo_no_mot_en_x w/r 0x00

0x17

int_fwm_en int_ffull_en data_en low_en high_en_z high_en_y high_en_x w/r 0x00

0x16 flat_en orient_en s_tap_en d_tap_en slope_en_z slope_en_y slope_en_x w/r 0x00

0x15 w/r 0xFF

0x14 wo 0x00

0x13 data_high_bw shadow_dis w/r 0x00

0x12 lowpower_mode sleeptimer_mode low_power_mode (reserved) w/r 0x00

0x11 suspend lowpower_en deep_suspend w/r 0x00

0x10 w/r 0x0F

0x0F w/r 0x03

0x0E

fifo_overrun ro 0x00

0x0D w/r 0xFF

0x0C flat high_sign high_first_z high_first_y high_first_x ro 0x00

0x0B tap_sign tap_first_z tap_first_y tap_first_x slope_sign slope_first_z slope_first_y slope_first_x ro 0x00

0x0A data_int

fifo_wm_int fifo_full_int ro 0x00

0x09 flat_int orient_int s_tap_int d_tap_int slo_no_mot_int slope_int high_int low_int ro 0x00

0x08 ro 0x00

0x07 ro 0x00

0x06 new_data_z ro 0x00

0x05 ro 0x00

0x04 new_data_y ro 0x00

0x03 ro 0x00

0x02 new_data_x ro 0x00

0x01 ro --

0x00 ro 0xFA

low_hy<1:0>

sleep_dur<3:0>

fifo_frame_counter<6:0>

orient<2:0>

temp<7:0>

low_dur<7:0>

bw<4:0>

range<3:0>

softreset

orient_hyst<2:0>

orient_theta<5:0>

fifo_data_select<1:0>

flat_hold_time<1:0>

nvm_remain<3:0>

GP1<7:0>

latch_int<3:0>

low_th<7:0>

flat_hy<2:0>

flat_theta<5:0>

slo_no_mot_th<7:0>

orient_mode<1:0>

tap_samp<1:0>

tap_th<4:0>

fifo_data_output_register<7:0>

GP0<7:0>

offset_z<7:0>

fifo_water_mark_level_trigger_retain<5:0>

offset_target_z<1:0>

cal_trigger<1:0>

offset_x<7:0>

fifo_mode<1:0>

offset_y<7:0>

acc_z_msb<11:4>

acc_x_lsb<3:0>

offset_target_y<1:0>

offset_target_x<1:0>

slope_dur<1:0>

slope_th<7:0>

high_dur<7:0>

tap_dur<2:0>

acc_y_lsb<3:0>

self_test_axis<1:0>

high_hy<1:0>

orient_blocking<1:0>

high_th<7:0>

slo_no_mot_dur<5:0>

chip_id<7:0>

acc_y_msb<11:4>

acc_x_msb<11:4>

acc_z_lsb<3:0>

common w/r registers: Application specific settings which are not equal to the default settings,

must be re-set to its designated values after POR, soft-reset and wake up from deep suspend.

user w/r registers: Initial default content = 0x00. Freely programmable by the user.

Remains unchanged after POR, soft-reset and wake up from deep suspend.

Figure 12: Register map

BMA255

Data sheet

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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.

Register 0x00 (BGW_CHIPID)

The register contains the chip identification code.

Name

0x00

BGW_CHIPID

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

chip_id<7:4>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

chip_id<3:0>

chip_id<7:0>: Fixed value b’1111’1010

Register 0x02 (ACCD_X_LSB)

The register contains the least-significant bits of the X-channel acceleration readout value.

When reading out X-channel acceleration values, data consistency is guaranteed if the

ACCD_X_LSB is read out before the ACCD_X_MSB and shadow_dis=’0’. In this case, after the

ACCD_X_LSB has been read, the value in the ACCD_X_MSB register is locked until the

ACCD_X_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_X_LSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x02

ACCD_X_LSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_x_lsb<3:0>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

undefined

new_data_x

acc_x_lsb<3:0>: Least significant 4 bits of acceleration read-back value; (two’s-complement

format)

undefined: random data; to be ignored.

new_data_x: ‚0’: acceleration value has not been updated since it has been read out last

‚1’: acceleration value has been updated since it has been read out last

BMA255

Data sheet

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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.

Register 0x03 (ACCD_X_MSB)

The register contains the most-significant bits of the X-channel acceleration readout value.

When reading out X-channel acceleration values, data consistency is guaranteed if the

ACCD_X_LSB is read out before the ACCD_X_MSB and shadow_dis=’0’. In this case, after the

ACCD_X_LSB has been read, the value in the ACCD_X_MSB register is locked until the

ACCD_X_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_X_MSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x02

ACCD_X_MSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_x_msb<11:8>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

acc_x_msb<7:4>

acc_x_msb<11:4>: Most significant 8 bits of acceleration read-back value (two’s-complement

format)

BMA255

Data sheet

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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.

Register 0x04 (ACCD_Y_LSB)

The register contains the least-significant bits of the Y-channel acceleration readout value.

When reading out Y-channel acceleration values, data consistency is guaranteed if the

ACCD_Y_LSB is read out before the ACCD_Y_MSB and shadow_dis=’0’. In this case, after the

ACCD_Y_LSB has been read, the value in the ACCD_Y_MSB register is locked until the

ACCD_Y_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_Y_LSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x04

ACCD_Y_LSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_y_lsb<3:0>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

undefined

new_data_y

acc_y_lsb<3:0>: Least significant 4 bits of acceleration read-back value; (two’s-complement

format)

undefined: random data; to be ignored

new_data_y: ‚0’: acceleration value has not been updated since it has been read out last

‚1’: acceleration value has been updated since it has been read out last

BMA255

Data sheet

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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.

Register 0x05 (ACCD_Y_MSB)

The register contains the most-significant bits of the Y-channel acceleration readout value.

When reading out Y-channel acceleration values, data consistency is guaranteed if the

ACCD_Y_LSB is read out before the ACCD_Y_MSB and shadow_dis=’0’. In this case, after the

ACCD_Y_LSB has been read, the value in the ACCD_Y_MSB register is locked until the

ACCD_Y_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_Y_MSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x05

ACCD_Y_MSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_y_msb<11:8>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

acc_y_msb<7:4>

acc_y_msb<11:4>: Most significant 8 bits of acceleration read-back value (two’s-complement

format)

BMA255

Data sheet

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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.

Register 0x06 (ACCD_Z_LSB)

The register contains the least-significant bits of the Z-channel acceleration readout value.

When reading out Z-channel acceleration values, data consistency is guaranteed if the

ACCD_Z_LSB is read out before the ACCD_Z_MSB and shadow_dis=’0’. In this case, after the

ACCD_Z_LSB has been read, the value in the ACCD_Z_MSB register is locked until the

ACCD_Z_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_Z_LSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x06

ACCD_Z_LSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_z_lsb<3:0>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

undefined

new_data_z

Acc_z_lsb<3:0>: Least significant 4 bits of acceleration read-back value; (two’s-complement

format)

undefined: random data; to be ignored

new_data_z: ‚0’: acceleration value has not been updated since it has been read out last

‚1’: acceleration value has been updated since it has been read out last

BMA255

Data sheet

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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.

Register 0x07 (ACCD_Z_MSB)

The register contains the most-significant bits of the Z-channel acceleration readout value.

When reading out Z-channel acceleration values, data consistency is guaranteed if the

ACCD_Z_LSB is read out before the ACCD_Z_MSB and shadow_dis=’0’. In this case, after the

ACCD_Z_LSB has been read, the value in the ACCD_Z_MSB register is locked until the

ACCD_Z_MSB has been read. This condition is inherently fulfilled if a burst-mode read access

is performed. Acceleration data may be read from register ACCD_Z_MSB at any time except

during power-up and in DEEP_SUSPEND mode.

Name

0x07

ACCD_Z_MSB

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

acc_z_msb<11:8>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

acc_z_msb<7:4>

acc_z_msb<11:4>: Most significant 8 bits of acceleration read-back value (two’s-complement

format)

BMA255

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Note: Specifications within this document are subject to change without notice.

Register 0x08 (ACCD_TEMP)

The register contains the current chip temperature represented in two’s complement format. A

readout value of temp<7:0>=0x00 corresponds to a temperature of 23°C.

Name

0x08

ACCD_TEMP

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

temp<7:4>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

temp<3:0>

temp<7:0>: Temperature value (two s-complement format)

BMA255

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Note: Specifications within this document are subject to change without notice.

Register 0x09 (INT_STATUS_0)

The register contains interrupt status flags. Each flag is associated with a specific interrupt

function. It is set when the associated interrupt triggers. The setting of latch_int<3:0> controls if

the interrupt signal and hence the respective interrupt flag will be permanently latched,

temporarily latched or not latched. The interrupt function associated with a specific status flag

must be enabled.

Name

0x09

INT_STATUS_0

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

flat_int

orient_int

s_tap_int

d_tap_int

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

slo_no_mot_int

slope_int

high_int

low_int

flat_int: flat interrupt status: ‘0’inactive, ‘1’ active

orient_int: orientation interrupt status: ‘0’inactive, ‘1’ active

s_tap_int: single tap interrupt status: ‘0’inactive, ‘1’ active

d_tap_int double tap interrupt status: ‘0’inactive, ‘1’ active

slo_not_mot_int: slow/no-motion interrupt status: ‘0’inactive, ‘1’ active

slope_int: slope interrupt status: ‘0’inactive, ‘1’ active

high_int: high-g interrupt status: ‘0’inactive, ‘1’ active

low_int: low-g interrupt status: ‘0’inactive, ‘1’ active

BMA255

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Note: Specifications within this document are subject to change without notice.

Register 0x0A (INT_STATUS_1)

The register contains interrupt status flags. Each flag is associated with a specific interrupt

function. It is set when the associated interrupt engine triggers. The setting of latch_int<3:0>

controls if the interrupt signal and hence the respective interrupt flag will be permanently

latched, temporarily latched or not latched. The interrupt function associated with a specific

status flag must be enabled.

Name

0x0A

INT_STATUS_1

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

data_int

fifo_wm_int

fifo_full_int

reserved

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

reserved

data_int: data ready interrupt status: ‘0’inactive, ‘1’ active

fifo_wm_int: FIFO watermark interrupt status: ‘0’inactive, ‘1’ active

fifo_full_int: FIFO full interrupt status: ‘0’inactive, ‘1’ active

reserved: reserved, write to ‘0’

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x0B (INT_STATUS_2)

The register contains interrupt status flags. Each flag is associated with a specific interrupt

engine. It is set when the associated interrupt engine triggers. The setting of latch_int<3:0>

controls if the interrupt signal and hence the respective interrupt flag will be permanently

latched, temporarily latched or not latched. The interrupt function associated with a specific

status flag must be enabled.

Name

0x0B

INT_STATUS_2

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

tap_sign

tap_first_z

tap_first_y

tap_first_x

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

slope_sign

slope_first_z

slope_first_y

slope_first_x

tap_sign: sign of single/double tap triggering signal was ‘0’positive, or ‘1’ negative

tap_first_z: single/double tap interrupt: ‘1’  triggered by, or ‘0’not triggered by z-axis

tap_first_y: single/double tap interrupt: ‘1’  triggered by, or ‘0’not triggered by y-axis

tap_first_x: single/double tap interrupt: ‘1’  triggered by, or ‘0’not triggered by x-axis

slope_sign: slope sign of slope tap triggering signal was ‘0’positive, or ‘1’ negative

slope_first_z: slope interrupt: ‘1’  triggered by, or ‘0’not triggered by z-axis

slope_first_y: slope interrupt: ‘1’  triggered by, or ‘0’not triggered by y-axis

slope_first_x: slope interrupt: ‘1’  triggered by, or ‘0’not triggered by x-axis

BMA255

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Note: Specifications within this document are subject to change without notice.

Register 0x0C (INT_STATUS_3)

The register contains interrupt status flags. Each flag is associated with a specific interrupt

engine. It is set when the associated interrupt engine triggers. With the exception of orient<3:0>

the setting of latch_int<3:0> controls if the interrupt signal and hence the respective interrupt

flag will be permanently latched, temporarily latched or not latched. The interrupt function

associated with a specific status flag must be enabled.

Name

0x0C

INT_STATUS_3

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

flat

orient<2:0>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

high_sign

high_first_z

high_first_y

high_first_x

flat: device is in ‘1’  flat, or ‘0’ non flat position;

only valid if (0x16) flat_en = ‘1’

orient<2>: Orientation value of z-axis: ´0´  upward looking, or ´1´  downward

looking. The flag always reflect the current orientation status, independent of

the setting of latch_int<3:0>. The flag is not updated as long as an

orientation blocking condition is active.

orient<1:0>: orientation value of x-y-plane:

‘00’portrait upright; ‘01’portrait upside down;

‘10’landscape left; ‘11’landscape right;

The flags always reflect the current orientation status, independent of the

setting of latch_int<3:0>. The flag is not updated as long as an orientation

blocking condition is active.

high_sign: sign of acceleration signal that triggered high-g interrupt was ‘0’positive, ‘1’

negative

high_first_z: high-g interrupt: ‘1’  triggered by, or ‘0’not triggered by z-axis

high_first_y: high-g interrupt: ‘1’  triggered by, or ‘0’not triggered by y-axis

high_first_x: high-g interrupt: ‘1’  triggered by, or ‘0’not triggered by x-axis

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x0E (FIFO_STATUS)

The register contains FIFO status flags.

Name

0x0E

FIFO_STATUS

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

fifo_overrun

fifo_frame_counter<6:4>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

fifo_frame_counter<3:0>

fifo_overrun: FIFO overrun condition has ‘1’  occurred, or ‘0’not occurred; flag can be

cleared by writing to the FIFO configuration register FIFO_CONFIG_1 only

fifo_frame_counter<6:4>: Current fill level of FIFO buffer. An empty FIFO corresponds to

0x00. The frame counter can be cleared by reading out all frames from the

FIFO buffer or writing to the FIFO configuration register FIFO_CONFIG_1.

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x0F (PMU_RANGE)

The register allows the selection of the accelerometer g-range.

Name

0x0F

PMU_RANGE

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

0

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

Content

range<3:0>

range<3:0>: Selection of accelerometer g-range:

´0011b´  ±2g range; ´0101b´  ±4g range; ´1000b´  ±8g range;

´1100b´  ±16g range; all other settings  reserved (do not use)

reserved: write ‘0’

Register 0x10 (PMU_BW)

The register allows the selection of the acceleration data filter bandwidth.

Name

0x10

PMU_BW

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

bw<4>

0

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

Content

bw<3:0>

bw<4:0>: Selection of data filter bandwidth:

´00xxxb´  7.81 Hz, ´01000b´  7.81 Hz, ´01001b´  15.63 Hz,

´01010b´  31.25 Hz, ´01011b´  62.5 Hz, ´01100b´  125 Hz,

´01101b´  250 Hz, ´01110b´  500 Hz, ´01111b´  1000 Hz,

´1xxxxb´  1000 Hz

reserved: write ‘0’

BMA255

Data sheet

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Register 0x11 (PMU_LPW)

Selection of the main power modes and the low power sleep period.

Name

0x11

PMU_LPW

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

suspend

lowpower_en

deep_suspend

sleep_dur<3>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

sleep_dur<2:0>

reserved

suspend, low_power_en, deep_suspend:

Main power mode configuration setting {suspend; lowpower_en;

deep_suspend}:

{0; 0; 0}  NORMAL mode;

{0; 0; 1}  DEEP_SUSPEND mode;

{0; 1; 0}  LOW_POWER mode;

{1; 0; 0}  SUSPEND mode;

{all other}  illegal

Please note that only certain power mode transitions are permitted.

sleep_dur<3:0>: Configures the sleep phase duration in LOW_POWER mode:

´0000b´ to ´0101b´  0.5 ms, ´0110b´  1 ms,

´0111b´  2 ms, ´1000b´  4 ms,

´1001b´  6 ms, ´1010b´  10 ms,

´1011b´  25 ms, ´1100b´  50 ms,

´1101b´  100 ms, ´1110b´  500 ms,

´1111b´  1 s

Please note, that all application specific settings which are not equal to the default settings

(refer to 6.2 register map), must be re-set to its designated values after DEEP_SUSPEND.

BMA255

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Register 0x12 (PMU_LOW_POWER)

Configuration settings for low power mode.

Name

0x12

PMU_LOW_POWER

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

lowpower_mode

sleeptimer_mode

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

lowpower_mode: select ‘0’  LPM1, or ‘1´  LPM2 configuration for SUSPEND and

LOW_POWER mode. In the LPM1 configuration the power consumption in

LOW_POWER mode and SUSPEND mode is significantly reduced when

compared to LPM2 configuration, but the FIFO is not accessible and writing

to registers must be slowed down. In the LPM2 configuration the power

consumption in LOW_POWER mode is reduced compared to NORMAL

mode, but the FIFO is fully accessible and registers can be written to at full

speed.

sleeptimer_mode: when in LOW_POWER mode ‘0’  use event-driven time-base mode

(compatible with BMA250), or ‘1´  use equidistant sampling time-base

mode. Equidistant sampling of data into the FIFO is maintained in

equidistant time-base mode only.

reserved: write ‘0’

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x13 (ACCD_HBW)

Acceleration data acquisition and data output format.

Name

0x13

ACCD_HBW

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

0 (1 in 8-bit

mode)

0

Content

data_high_bw

shadow_dis

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

data_high_bw: select whether ‘1´ unfiltered, or ‘0’ filtered data may be read from the

acceleration data registers.

shadow_dis: ‘1´ disable, or ‘0’ the shadowing mechanism for the acceleration data

output registers. When shadowing is enabled, the content of the acceleration

data component in the MSB register is locked, when the component in the

LSB is read, thereby ensuring the integrity of the acceleration data during

read-out. The lock is removed when the MSB is read.

reserved: write ‘0’

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x14 (BGW_SOFTRESET)

Controls user triggered reset of the sensor.

Name

0x14

BGW_SOFTRESET

Bit

7

6

5

4

Read/Write

W

Reset

Value

0

Content

softreset

Bit

3

2

1

0

Read/Write

W

Reset

Value

0

Content

softreset

softreset: 0xB6  triggers a reset. Other values are ignored. Following a delay, all

user configuration settings are overwritten with their default state or the

setting stored in the NVM, wherever applicable. This register is functional in

all operation modes. Please note that all application specific settings which

are not equal to the default settings (refer to 6.2 register map), must be

reconfigured to their designated values.

Register 0x16 (INT_EN_0)

Controls which interrupt engines in group 0 are enabled.

Name

0x16

INT_EN_0

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

flat_en

orient_en

s_tap_en

d_tap_en

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

slope_en_z

slope_en_y

slope_en_x

flat_en: flat interrupt: ‘0’disabled, or ‘1’ enabled

orient_en: orientation interrupt: ‘0’disabled, or ‘1’ enabled

s_tap_en: single tap interrupt: ‘0’disabled, or ‘1’ enabled

d_tap_en double tap interrupt: ‘0’disabled, or ‘1’ enabled

reserved: write ‘0’

slope_en_z: slope interrupt, z-axis component: ‘0’disabled, or ‘1’ enabled

slope_en_y: slope interrupt, y-axis component: ‘0’disabled, or ‘1’ enabled

slope_en_x: slope interrupt, x-axis component: ‘0’disabled, or ‘1’ enabled

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x17 (INT_EN_1)

Controls which interrupt engines in group 1 are enabled.

Name

0x17

INT_EN_1

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

int_fwm_en

int_ffull_en

data_en

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

low_en

high_en_z

high_en_y

high_en_x

reserved: write ‘0’

int_fwm_en: FIFO watermark interrupt: ‘0’disabled, or ‘1’ enabled

int_ffull_en: FIFO full interrupt: ‘0’disabled, or ‘1’ enabled

data_en data ready interrupt: ‘0’disabled, or ‘1’ enabled

low_en: low-g interrupt: ‘0’disabled, or ‘1’ enabled

high_en_z: high-g interrupt, z-axis component: ‘0’disabled, or ‘1’ enabled

high_en_y: high-g interrupt, y-axis component: ‘0’disabled, or ‘1’ enabled

high_en_x: high-g interrupt, x-axis component: ‘0’disabled, or ‘1’ enabled

BMA255

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Register 0x18 (INT_EN_2)

Controls which interrupt engines in group 2 are enabled.

Name

0x18

INT_EN_2

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

slo_no_mot_sel

slo_no_mot_en_z

slo_no_mot_en_y

slo_no_mot_en_x

reserved: write ‘0’

slo_no_mot_sel: select ‘0’slow-motion, ‘1’ no-motion interrupt function

slo_no_mot_en_z: slow/n-motion interrupt, z-axis component: ‘0’disabled, or ‘1’ enabled

slo_no_mot_en_y: slow/n-motion interrupt, y-axis component: ‘0’disabled, or ‘1’ enabled

slo_no_mot_en_x: slow/n-motion interrupt, x-axis component: ‘0’disabled, or ‘1’ enabled

BMA255

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Register 0x19 (INT_MAP_0)

Controls which interrupt signals are mapped to the INT1 pin.

Name

0x19

INT_MAP_0

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

int1_flat

int1_orient

int1_s_tap

int1_d_tap

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

int1_slo_no_mot

int1_slope

int1_high

int1_low

int1_flat: map flat interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_orient: map orientation interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_s_tap: map single tap interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_d_tap: map double tap interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_slo_no_mot: map slow/no-motion interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_slope: map slope interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_high: map high-g to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_low: map low-g to INT1 pin: ‘0’disabled, or ‘1’ enabled

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Register 0x1A (INT_MAP_1)

Controls which interrupt signals are mapped to the INT1 and INT2 pins.

Name

0x1A

INT_MAP_1

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

int2_data

int2_fwm

int2_ffull

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

int1_ffull

int1_fwm

int1_data

int2_data: map data ready interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_fwm: map FIFO watermark interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_ffull: map FIFO full interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

reserved: write ‘0’

int1_ffull: map FIFO full interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_fwm: map FIFO watermark interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

int1_data: map data ready interrupt to INT1 pin: ‘0’disabled, or ‘1’ enabled

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Register 0x1B (INT_MAP_2)

Controls which interrupt signals are mapped to the INT2 pin.

Name

0x1B

INT_MAP_2

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

int2_flat

int2_orient

int2_s_tap

int2_d_tap

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

int2_slo_no_mot

int2_slope

int2_high

int2_low

int2_flat: map flat interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_orient: map orientation interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_s_tap: map single tap interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_d_tap: map double tap interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_slo_no_mot: map slow/no-motion interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_slope: map slope interrupt to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_high: map high-g to INT2 pin: ‘0’disabled, or ‘1’ enabled

int2_low: map low-g to INT2 pin: ‘0’disabled, or ‘1’ enabled

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Register 0x1E (INT_SRC)

Contains the data source definition for interrupts with selectable data source.

Name

0x1E

INT_SRC

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

int_src_data

int_src_tap

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

int_src_slo_no_m

ot

int_src_slope

int_src_high

int_src_low

reserved: write ‘0’

int_src_data: select ‘0’filtered, or ‘1’ unfiltered data for new data interrupt

int_src_tap: select ‘0’filtered, or ‘1’ unfiltered data for single-/double tap interrupt

int_src_slo_no_mot: select ‘0’filtered, or ‘1’ unfiltered data for slow/no-motion interrupt

int_src_slope: select ‘0’filtered, or ‘1’ unfiltered data for slope interrupt

int_src_high: select ‘0’filtered, or ‘1’ unfiltered data for high-g interrupt

int_src_low: select ‘0’filtered, or ‘1’ unfiltered data for low-g interrupt

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Register 0x20 (INT_OUT_CTRL)

Contains the behavioural configuration (electrical behaviour) of the interrupt pins.

Name

0x20

INT_OUT_CTRL

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

0

1

Content

int2_od

int2_lvl

int1_od

int1_lvl

reserved: write ‘0’

int2_od: select ‘0’push-pull, or ‘1’ open drain behavior for INT2 pin

int2_lvl: select ‘0’active low, or ‘1’active high level for INT2 pin

int1_od: select ‘0’push-pull, or ‘1’ open drain behavior for INT1 pin

int1_lvl: select ‘0’active low, or ‘1’active high level for INT1 pin

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Register 0x21 (INT_RST_LATCH)

Contains the interrupt reset bit and the interrupt mode selection.

Name

0x21

INT_RST_LATCH

Bit

7

6

5

4

Read/Write

W

R/W

Reset

Value

0

Content

reset_int

Reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

latch_int<3:0>

reset_int: write ‘1’  clear any latched interrupts, or ‘0’  keep latched interrupts

active

reserved: write ‘0’

latch_int<3:0>: ´0000b´  non-latched, ´0001b´  temporary, 250 ms,

´0010b´  temporary, 500 ms, ´0011b´  temporary, 1 s,

´0100b´  temporary, 2 s, ´0101b´  temporary, 4 s,

´0110b´  temporary, 8 s, ´0111b´  latched,

´1000b´  non-latched, ´1001b´  temporary, 250 s,

´1010b´  temporary, 500 s, ´1011b´  temporary, 1 ms,

´1100b´  temporary, 12.5 ms, ´1101b´  temporary, 25 ms,

´1110b´  temporary, 50 ms, ´1111b´  latched

Register 0x22 (INT_0)

Contains the delay time definition for the low-g interrupt.

Name

0x22

INT_0

Bit

7

6

5

4

Read/Write

W

R/W

Reset

Value

0

Content

low_dur<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

0

1

Content

low_dur<3:0>

low_dur<7:0>: low-g interrupt trigger delay according to [low_dur<7:0> + 1] • 2 ms in a

range from 2 ms to 512 ms; the default corresponds to a delay of 20 ms.

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Register 0x23 (INT_1)

Contains the threshold definition for the low-g interrupt.

Name

0x23

INT_1

Bit

7

6

5

4

Read/Write

W

R/W

Reset

Value

0

1

Content

low_th<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

low_th<3:0>

low_th<7:0>: low-g interrupt trigger threshold according to low_th<7:0> • 7.81 mg in a

range from 0 g to 1.992 g; the default value corresponds to an acceleration

of 375 mg

Register 0x24 (INT_2)

Contains the low-g interrupt mode selection, the low-g interrupt hysteresis setting, and the high-

g interrupt hysteresis setting.

Name

0x24

INT_2

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

1

0

Content

high_hy<1:0>

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

Content

reserved

low_mode

low_hy<1:0>

high_hy<1:0>: hysteresis of high-g interrupt according to high_hy<1:0> · 125 mg (2-g

range), high_hy<1:0> · 250 mg (4-g range), high_hy<1:0> · 500 mg (8-g

range), or high_hy<1:0> · 1000 mg (16-g range)

low_mode: select low-g interrupt ‘0’ single-axis mode, or ‘1’ axis-summing mode

low_hy<1:0>: hysteresis of low-g interrupt according to low_hy<1:0> · 125 mg independent

of the selected accelerometer g-range

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x25 (INT_3)

Contains the delay time definition for the high-g interrupt.

Name

0x25

INT_3

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

high_dur<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

Content

high_dur<3:0>

high_dur<7:0>: high-g interrupt trigger delay according to [high_dur<7:0> + 1] • 2 ms in a

range from 2 ms to 512 ms; the default corresponds to a delay of 32 ms.

Register 0x26 (INT_4)

Contains the threshold definition for the high-g interrupt.

Name

0x26

INT_4

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

1

0

Content

high_th<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

high_th<3:0>

high_th<7:0>: threshold of high-g interrupt according to high_th<7:0> · 7.81 mg (2-g range),

high_th<7:0> · 15.63 mg (4-g range), high_th<7:0> · 31.25 mg (8-g range),

or high_th<7:0> · 62.5 mg (16-g range)

BMA255

Data sheet

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Register 0x27 (INT_5)

Contains the definition of the number of samples to be evaluated for the slope interrupt (any-

motion detection) and the slow/no-motion interrupt trigger delay.

Name

0x27

INT_5

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

slo_no_mot_dur<5:2>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

slo_no_mot_dur<1:0>

slope_dur<1:0>

slo_no_mot_dur<5:0>: Function depends on whether the slow-motion or no-motion

interrupt function has been selected. If the slow-motion interrupt function has

been enabled (slo_no_mot_sel = ‘0’) then [slo_no_mot_dur<1:0>+1]

consecutive slope data points must be above the slow/no-motion threshold

(slo_no_mot_th) for the slow-/no-motion interrupt to trigger. If the no-motion

interrupt function has been enabled (slo_no_mot_sel = ‘1’) then

slo_no_motion_dur<5:0> defines the time for which no slope data points

must exceed the slow/no-motion threshold (slo_no_mot_th) for the slow/no-

motion interrupt to trigger. The delay time in seconds may be calculated

according with the following equation:

slo_no_mot_dur<5:4>=’b00’  [slo_no_mot_dur<3:0> + 1]

slo_no_mot_dur<5:4>=’b01’  [slo_no_mot_dur<3:0> · 4 + 20]

slo_no_mot_dur<5>=’1’  [slo_no_mot_dur<4:0> · 8 + 88]

slope_dur<1:0>: slope interrupt triggers if [slope_dur<1:0>+1] consecutive slope data points

are above the slope interrupt threshold slope_th<7:0>

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x28 (INT_6)

Contains the threshold definition for the any-motion interrupt.

Name

0x28

INT_6

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

1

Content

slope_th<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

0

Content

slope_th<3:0>

slope_th<7:0>: Threshold of the any-motion interrupt. It is range-dependent and defined as a

sample-to-sample difference according to

slope_th<7:0> · 3.91 mg (2-g range) /

slope_th<7:0> · 7.81 mg (4-g range) /

slope_th<7:0> · 15.63 mg (8-g range) /

slope_th<7:0> · 31.25 mg (16-g range)

Register 0x29 (INT_7)

Contains the threshold definition for the slow/no-motion interrupt.

Name

0x29

INT_7

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

1

Content

slo_no_mot_th<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

0

Content

slo_no_mot_th<3:0>

slo_no_mot_th<7:0>: Threshold of slow/no-motion interrupt. It is range-dependent and defined

as a sample-to-sample difference according to

slo_no_mot_th<7:0> · 3.91 mg (2-g range),

slo_no_mot_th<7:0> · 7.81 mg (4-g range),

slo_no_mot_th<7:0> · 15.63 mg (8-g range),

slo_no_mot_th<7:0> · 31.25 mg (16-g range)

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x2A (INT_8)

Contains the timing definitions for the single tap and double tap interrupts.

Name

0x2A

INT_8

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

tap_quiet

tap_shock

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

0

Content

reserved

tap_dur<2:0>

tap_quiet: selects a tap quiet duration of ‘0’ 30 ms, ‘1’ 20 ms

tap_shock: selects a tap shock duration of ‘0’ 50 ms, ‘1’75 ms

reserved: write ‘0’

tap_dur<2:0>: selects the length of the time window for the second shock event for double

tap detection according to ´000b´  50 ms, ´001b´  100 ms, ´010b´  150

ms, ´011b´  200 ms, ´100b´  250 ms, ´101b´  375 ms, ´110b´  500

ms, ´111b´  700 ms.

BMA255

Data sheet

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Register 0x2B (INT_9)

Contains the definition of the number of samples processed by the single / double-tap interrupt

engine after wake-up in low-power mode. It also defines the threshold definition for the single

and double tap interrupts.

Name

0x2B

INT_9

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

tap_samp<1:0>

reserved

tap_th<4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

0

1

0

Content

tap_th<3:0>

tap_samp<1:0>: selects the number of samples that are processed after wake-up in the low-

power mode according to ´00b´  2 samples, ´01b´  4 samples, ´10b´  8

samples, and ´11b´  16 samples

reserved: write ‘0’

tap_th<4:0>: threshold of the single/double-tap interrupt corresponding to an acceleration

difference of tap_th<4:0> · 62.5mg (2g-range), tap_th<4:0> · 125mg (4g-

range), tap_th<4:0> · 250mg (8g-range), and tap_th<4:0> · 500mg (16g-

range).

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x2C (INT_A)

Contains the definition of hysteresis, blocking, and mode for the orientation interrupt

Name

0x2C

INT_A

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

1

Content

reserved

orient_hyst<2:0>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

0

Content

orient_blocking<1:0>

orient_mode<1:0>

reserved: write ‘0’

orient_hyst<2:0>: sets the hysteresis of the orientation interrupt; 1 LSB corresponds to 62.5 mg

irrespective of the selected g-range

orient_blocking<1:0>: selects the blocking mode that is used for the generation of the

orientation interrupt. The following blocking modes are available:

´00b´  no blocking,

´01b´  theta blocking or acceleration in any axis > 1.5g,

´10b´  ,theta blocking or acceleration slope in any axis > 0.2 g or

acceleration in any axis > 1.5g

´11b´  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 100ms

orient_mode<1:0>: sets the thresholds for switching between the different orientations. The

settings: ´00b´  symmetrical, ´01b´  high-asymmetrical, ´10b´  low-

asymmetrical, ´11b´ symmetrical.

BMA255

Data sheet

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Register 0x2D (INT_B)

Contains the definition of the axis orientation, up/down masking, and the theta blocking angle

for the orientation interrupt.

Name

0x2D

INT_B

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

n/a

1

0

Content

reserved

orient_ud_en

orient_theta<5:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

0

Content

orient_theta<3:0>

orient_ud_en: change of up/down-bit ´1´  generates an orientation interrupt, ´0´  is

ignored and will not generate an orientation interrupt

orient_theta<5:0>: defines a blocking angle between 0° and 44.8°

Register 0x2E (INT_C)

Contains the definition of the flat threshold angle for the flat interrupt.

Name

0x2E

INT_C

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

n/a

0

Content

reserved

flat_theta<5:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

1

0

Content

flat_theta<3:0>

reserved: write ‘0’

flat_theta<5:0>: defines threshold for detection of flat position in range from 0° to 44.8°.

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x2F (INT_D)

Contains the definition of the flat interrupt hold time and flat interrupt hysteresis.

Name

0x2F

INT_D

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

1

Content

reserved

flat_hold_time<1:0>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

1

Content

reserved

flat_hy<2:0>

reserved: write ‘0’

flat_hold_time<1:0>: delay time for which the flat value must remain stable for the flat interrupt

to be generated: ´00b´  0 ms, ´01b´  512 ms, ´10b´  1024 ms,

´11b´  2048 ms

flat_hy<2:0>: defines flat interrupt hysteresis; flat value must change by more than twice

the value of flat interrupt hysteresis to detect a state change. For details see

chapter 4.7.8.

‘000b’  hysteresis of the flat detection disabled

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x30 (FIFO_CONFIG_0)

Contains the FIFO watermark level.

Name

0x30

FIFO_CONFIG_0

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

n/a

0

Content

reserved

fifo_water_mark_level_trigger_retain<

5:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

fifo_water_mark_level_trigger_retain<3:0>

reserved: write ‘0’

fifo_water_mark_level_trigger_retain<5:0>:

fifo_water_mark_level_trigger_retain<5:0> defines the FIFO watermark level.

An interrupt will be generated, when the number of entries in the FIFO is

equal to fifo_water_mark_level_trigger_retain<5:0>;

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x32 (PMU_SELF_TEST)

Contains the settings for the sensor self-test configuration and trigger.

Name

0x32

PMU_SELF_TEST

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

self_test_sign

self_test-axis<1:0>

reserved: write ‘0x0’

self_test_sign: select sign of self-test excitation as ´1´  positive, or ´0´  negative

self_test_axis: select axis to be self-tested: ´00b´  self-test disabled, ´01b´  x-axis, ´10b´

 y-axis, or ´11b´  z-axis; when a self-test is performed, only the

acceleration data readout value of the selected axis is valid; after the self-

test has been enabled a delay of a least 50 ms is necessary for the read-out

value to settle

BMA255

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Register 0x33 (TRIM_NVM_CTRL)

Contains the control settings for the few-time programmable non-volatile memory (NVM).

Name

0x33

TRIM_NVM_CTRL

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

nvm_remain<3:0>

Bit

3

2

1

0

Read/Write

R/W

R

W

R/W

Reset

Value

0

n/a

0

Content

nvm_load

nvm_rdy

nvm_prog_trig

nvm_prog_mode

nvm_remain<3:0>: number of remaining write cycles permitted for NVM; the number is

decremented each time a write to the NVM is triggered

nvm_load: ´1´  trigger, or ‘0’  do not trigger an update of all configuration registers

from NVM; the nvm_rdy flag must be ‘1’ prior to triggering the update

nvm_rdy: status of NVM controller: ´0´  NVM write / NVM update operation is in

progress, ´1´  NVM is ready to accept a new write or update trigger

nvm_prog_trig: ‘1’  trigger, or ‘0’ do not trigger an NVM write operation; the trigger is

only accepted if the NVM was unlocked before and nvm_remain<3:0> is

greater than ‘0’; flag nvm_rdy must be ‘1’ prior to triggering the write cycle

nvm_prog_mode: ‘1’  unlock, or ‘0’  lock NVM write operation

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x34 (BGW_SPI3_WDT)

Contains settings for the digital interfaces.

Name

0x34

BGW_SPI3_WDT

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

i2c_wdt_en

i2c_wdt_sel

spi3

reserved: write ‘0’

i2c_wdt_en: if I²C interface mode is selected then ‘1´  enable, or ‘0’  disables the

watchdog at the SDI pin (= SDA for I²C)

i2c_wdt_sel: select an I²C watchdog timer period of ‘0’  1 ms, or ‘1’  50 ms

spi3: select ´0´  4-wire SPI, or ´1´  3-wire SPI mode

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Note: Specifications within this document are subject to change without notice.

Register 0x36 (OFC_CTRL)

Contains control signals and configuration settings for the fast and the slow offset

compensation.

Name

0x36

OFC_CTRL

Bit

7

6

5

4

Read/Write

W

R

Reset

Value

0

Content

offset_reset

cal_trigger<1:0>

cal_rdy

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

reserved

hp_z_en

hp_y_en

hp_x_en

offset_reset: ´1´  set all offset compensation registers (0x38 to 0x3A) to zero, or ‘0’ 

keep their values

offset_trigger<1:0>: trigger fast compensation for ´01b´  x-axis, ´10b´  y-axis, or ´11b´ 

z-axis; ´00b´  do not trigger offset compensation; offset compensation

must not be triggered when cal_rdy is ‘0’

cal_rdy: indicates the state of the fast compensation: ´0´  offset compensation is in

progress, or ´1´  offset compensation is ready to be retriggered

reserved: write ‘0’

hp_z_en: ‘1´  enable, or ‘0’  disable slow offset compensation for the z-axis

hp_y_en: ‘1´  enable, or ‘0’  disable slow offset compensation for the y-axis

hp_x_en: ‘1´  enable, or ‘0’  disable slow offset compensation for the x-axis

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Register 0x37 (OFC_SETTING)

Contains configuration settings for the fast and the slow offset compensation.

Name

0x37

OFC_SETTING

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

reserved

offset_target_z<1:0>

offset_target_y<1

>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

offset_target_y<0

>

offset_target_x<1:0>

cut_off

reserved: write ‘0’

offset_target_z<1:0>: offset compensation target value for z-axis is ´00b´  0 g, ´01b´  +1 g,

´10b´  -1 g, or ´11b´  0 g

offset_target_y<1:0>: offset compensation target value for y-axis is ´00b´  0 g, ´01b´  +1 g,

´10b´  -1 g, or ´11b´  0 g

offset_target_x<1:0>: offset compensation target value for x-axis is ´00b´  0 g, ´01b´  +1 g,

´10b´  -1 g, or ´11b´  0 g

cut_off:

(0x37)

cut_off

high-pass filter

bandwidth

Example

bw = 500 Hz

0b

1b

*bw: please insert selected decimal data bandwidth value [Hz] from table 4

BMA255

Data sheet

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Note: Specifications within this document are subject to change without notice.

Register 0x38 (OFC_OFFSET_X)

Contains the offset compensation value for x-axis acceleration readout data.

Name

0x38

OFC_OFFSET_X

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

offset_x<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

offset_x<3:0>

offset_ x<7:0>: offset value, which is subtracted from the internal filtered and unfiltered x-

axis acceleration data; the offset value is represented with two’s complement

notation, with a mapping of +127  +0.992g, 0  0 g, and -128  -1 g; the

scaling is independent of the selected g-range; the content of the

offset_x<7:0> may be written to the NVM; it is automatically restored from

the NVM after each power-on or softreset; offset_x<7:0> may be written

directly by the user; it is generated automatically after triggering the fast

offset compensation procedure for the x-axis

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Register 0x39 (OFC_OFFSET_Y)

Contains the offset compensation value for y-axis acceleration readout data.

Name

0x39

OFC_OFFSET_Y

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

offset_y<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

offset_y<3:0>

offset_ y<7:0>: offset value, which is subtracted from the internal filtered and unfiltered y-

axis acceleration data; the offset value is represented with two’s complement

notation, with a mapping of +127  +0.992g, 0  0 g, and -128  -1 g; the

scaling is independent of the selected g-range; the content of the

offset_y<7:0> may be written to the NVM; it is automatically restored from

the NVM after each power-on or softreset; offset_y<7:0> may be written

directly by the user; it is generated automatically after triggering the fast

offset compensation procedure for the y-axis

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Register 0x3A (OFC_OFFSET_Z)

Contains the offset compensation value for z-axis acceleration readout data.

Name

0x3A

OFC_OFFSET_Z

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

offset_z<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

offset_z<3:0>

offset_ z<7:0>: offset value, which is subtracted from the internal filtered and unfiltered z-

axis acceleration data; the offset value is represented with two’s complement

notation, with a mapping of +127  +0.992g, 0  0 g, and -128  -1 g; the

scaling is independent of the selected g-range; the content of the

offset_z<7:0> may be written to the NVM; it is automatically restored from

the NVM after each power-on or softreset; offset_z<7:0> may be written

directly by the user; it is generated automatically after triggering the fast

offset compensation procedure for the z-axis

Register 0x3B (TRIM_GP0)

Contains general purpose data register with NVM back-up.

Name

0x3B

TRIM_GP0

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

GP0<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

GP0<3:0>

GP0<7:0>: general purpose NVM image register not linked to any sensor-specific

functionality; register may be written to NVM and is restored after each

power-up or softreset

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Register 0x3C (TRIM_GP1)

Contains general purpose data register with NVM back-up.

Name

0x3C

TRIM_GP1

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

GP1<7:4>

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

GP1<3:0>

GP1<7:0>: general purpose NVM image register not linked to any sensor-specific

functionality; register may be written to NVM and is restored after each

power-up or softreset

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Register 0x3E (FIFO_CONFIG_1)

Contains FIFO configuration settings. The FIFO buffer memory is cleared and the fifo-full flag is

cleared when writing to FIFO_CONFIG_1 register.

Name

0x3E

FIFO_CONFIG_1

Bit

7

6

5

4

Read/Write

R/W

Reset

Value

0

Content

fifo_mode<1:0>

Reserved

Bit

3

2

1

0

Read/Write

R/W

Reset

Value

0

Content

Reserved

fifo_data_select<1:0>

fifo_mode<1:0>: selects the FIFO operating mode:

´00b´  BYPASS (buffer depth of 1 frame; old data is discarded),

´01b´  FIFO (data collection stops when buffer is filled with 32 frames),

´10b´  STREAM (sampling continues when buffer is full; old is discarded),

´11b´  reserved, do not use

fifo_data_select<1:0>: selects whether ´00b´  X+Y+Z, ´01b´  X only, ´10b´  Y only,

´11b´  Z only acceleration data are stored in the FIFO

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Register 0x3F (FIFO_DATA)

FIFO data readout register. The format of the LSB and MSB components corresponds to that of

the acceleration data readout registers. The new data flag is preserved. Read burst access may

be used since the address counter will not increment when the read burst is started at the

address of FIFO_DATA. The entire frame is discarded when a fame is only partially read out.

Name

0x3F

FIFO_DATA

Bit

7

6

5

4

Read/Write

R

Reset

Value

n/a

Content

fifo_data_output_register<7:4>

Bit

3

2

1

0

Read/Write

R

Reset

Value

n/a

Content

fifo_data_output_register<3:0>

fifo_data_output_register<7:0>: FIFO data readout; data format depends on the setting of

register fifo_data_select<1:0>:

if X+Y+Z data are selected, the data of frame n is reading out in the order of

X-lsb(n), X-msb(n), Y-lsb(n), Y-msb(n), Z-lsb(n), Z-msb(n);

if X-only is selected, the data of frame n and n+1 are reading out in the order

of X-lsb(n), X-msb(n), X-lsb(n+1), X-msb(n+1); the Y-only and Z-only modes

behave analogously

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7. Digital interfaces

The BMA255 supports two serial digital interface protocols for communication as a slave with a

host device (when operating in general mode): SPI and I²C. The active interface is selected by

the state of the Pin#11 (PS) ‘protocol select’ pin: ´0´ (´1´) selects SPI (I²C). For details please

refer to section 8).

By default, SPI operates in the standard 4-wire configuration. It can be re-configured by

software to work in 3-wire mode instead of standard 4-wire mode.

Both interfaces share the same pins. The mapping for each interface is given in the following

table:

Table 20: Mapping of the interface pins

Pin#

Name

use w/

SPI

use w/

I²C

Description

1

SDO

address

SPI: Data Output (4-wire mode)

I²C: Used to set LSB of I²C address

2

SDx

SDI

SDA

SPI: Data Input (4-wire mode) Data Input / Output (3-wire

mode)

I²C: Serial Data

10

CSB

unused

Chip Select (enable)

12

SCx

SCK

SCL

SPI: Serial Clock

I²C: Serial Clock

The following table shows the electrical specifications of the interface pins:

Table 21: Electrical specification of the interface pins

Parameter

Symbol

Condition

Min

Typ

Max

Units

Pull-up Resistance,

CSB pin

Rup

Internal Pull-up

Resistance to

VDDIO

75

100

125

k

Input Capacitance

Cin

5

10

pF

I²C Bus Load

Capacitance (max.

drive capability)

CI2C_Load

400

pF

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7.1 Serial peripheral interface (SPI)

The timing specification for SPI of the BMA255 is given in the following table:

Table 22: SPI timing

Parameter

Symbol

Condition

Min

Max

Units

Clock Frequency

fSPI

Max. Load on SDI

or SDO = 25pF,

VDDIO ≥ 1.62V

10

MHz

VDDIO < 1.62V

7.5

MHz

SCK Low Pulse

tSCKL

20

ns

SCK High Pulse

tSCKH

20

ns

SDI Setup Time

tSDI_setup

20

ns

SDI Hold Time

tSDI_hold

20

ns

SDO Output Delay

tSDO_OD

Load = 25pF,

VDDIO ≥ 1.62V

30

ns

Load = 25pF,

VDDIO < 1.62V

50

ns

Load = 250pF,

VDDIO > 2.4V

40

ns

CSB Setup Time

tCSB_setup

20

ns

CSB Hold Time

tCSB_hold

40

ns

Idle time between

write accesses, normal

mode, standby mode,

low-power mode 2

tIDLE_wacc_nm

2

µs

Idle time between

write accesses,

suspend mode, low-

power mode 1

tIDLE_wacc_sum

450

µs

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The following figure shows the definition of the SPI timings given in the following figure:

tSDI_hold

tSCKH

tCSB_hold

tCSB_setup

tSDI_setup

tSCKL

tSDO_OD

CSB

SCK

SDI

SDO

Figure 13: SPI timing diagram

The SPI interface of the BMA255 is compatible with two modes, ´00´ and ´11´. The automatic

selection between [CPOL = ´0´ and CPHA = ´0´] and [CPOL = ´1´ and CPHA = ´1´] is controlled

based on the value of SCK after a falling edge of CSB.

Two configurations of the SPI interface are supported by the BMA255: 4-wire and 3-wire. The

same protocol is used by both configurations. The device operates in 4-wire configuration by

default. It can be switched to 3-wire configuration by writing ´1´ to (0x34) spi3. Pin SDI is used

as the common data pin in 3-wire configuration.

For single byte read as well as write operations, 16-bit protocols are used. The BMA255 also

supports multiple-byte read operations.

In SPI 4-wire configuration CSB (chip select low active), SCK (serial clock), SDI (serial data

input), and SDO (serial data output) pins are used. The communication starts when the CSB is

pulled low by the SPI master and stops when CSB is pulled high. SCK is also controlled by SPI

master. SDI and SDO are driven at the falling edge of SCK and should be captured at the rising

edge of SCK.

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The basic write operation waveform for 4-wire configuration is depicted in figure 14. During the

entire write cycle SDO remains in high- impedance state.

CSB

SCK

SDI

R/W

AD6

AD5

AD4

AD3

AD2

AD1

AD0

DI5

DI4

DI3

DI2

DI1

DI0

DI7

DI6

SDO

tri-state

Z

Figure 14: 4-wire basic SPI write sequence (mode ´11´)

The basic read operation waveform for 4-wire configuration is depicted in figure 15:

CSB

SCK

SDI

R/W

AD6

AD5

AD4

AD3

AD2

AD1

AD0

SDO

DO5

DO4

DO3

DO2

DO1

DO0

DO7

DO6

tri-state

Figure 15: 4-wire basic SPI read sequence (mode ´11´)

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The data bits are used as follows:

Bit0: Read/Write bit. When 0, the data SDI is written into the chip. When 1, the data SDO from

the chip is read.

Bit1-7: Address AD(6:0).

Bit8-15: when in write mode, these are the data SDI, which will be written into the address.

When in read mode, these are the data SDO, which are read from the address.

Multiple read operations are possible by keeping CSB low and continuing the data transfer.

Only the first register address has to be written. Addresses are automatically incremented after

each read access as long as CSB stays active low.

The principle of multiple read is shown in figure 16:

Start

RW Stop

1 0 0 0 0 0 1 0 X X X X X X X X X X X X X X X X X X X X X X X X

Register adress (02h)

CSB

=

0

CSB

=

1

Data byte

Data register - adress 03h

Data register - adress 04h

Control byte

Data byte

Data register - adress 02h

Figure 16: SPI multiple read

In SPI 3-wire configuration CSB (chip select low active), SCK (serial clock), and SDI (serial

data input and output) pins are used. The communication starts when the CSB is pulled low by

the SPI master and stops when CSB is pulled high. SCK is also controlled by SPI master. SDI

is driven (when used as input of the device) at the falling edge of SCK and should be captured

(when used as the output of the device) at the rising edge of SCK.

The protocol as such is the same in 3-wire configuration as it is in 4-wire configuration. The

basic operation waveform (read or write access) for 3-wire configuration is depicted in figure 17:

CSB

SCK

SDI

RW

AD6

AD5

AD4

AD3

AD2

AD1

AD0

DI5

DI4

DI3

DI2

DI1

DI0

DI7

DI6

Figure 17: 3-wire basic SPI read or write sequence (mode ´11´)

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7.2 Inter-Integrated Circuit (I²C)

The I²C bus uses SCL (= SCx pin, serial clock) and SDA (= SDx pin, serial data input and

output) signal lines. Both lines are connected to VDDIO externally via pull-up resistors so that they

are pulled high when the bus is free.

The I²C interface of the BMA255 is compatible with the I²C Specification UM10204 Rev. 03 (19

June 2007), available at http://www.nxp.com. The BMA255 supports I²C standard mode and

fast mode, only 7-bit address mode is supported.

The default I²C address of the device is 0011000b (0x18). It is used if the SDO pin is pulled to

´GND´. The alternative address 0011001b (0x19) is selected by pulling the SDO pin to ´VDDIO´.

The timing specification for I²C of the BMA255 is given in Table 23:

Table 23: I²C timings

Parameter

Symbol

Condition

Min

Max

Units

Clock Frequency

fSCL

400

kHz

SCL Low Period

tLOW

1.3

s

SCL High Period

tHIGH

0.6

SDA Setup Time

tSUDAT

0.1

SDA Hold Time

tHDDAT

0.0

Setup Time for a

repeated Start

Condition

tSUSTA

0.6

Hold Time for a Start

Condition

tHDSTA

0.6

Setup Time for a Stop

Condition

tSUSTO

0.6

Time before a new

Transmission can

start

tBUF

1.3

Idle time between

write accesses,

normal mode, standby

mode, low-power

mode 2

tIDLE_wacc_n

m

2

µs

Idle time between

write accesses,

suspend mode, low-

power mode 1

tIDLE_wacc_s

um

450

µs

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Figure 18 shows the definition of the I²C timings given in Table 23:

tHDDAT

tf

tBUF

SDA

SCL

SDA

tLOW

tHDSTA

tr

tSUSTA

tHIGH

tSUDAT

tSUSTO

Figure 18: I²C timing diagram

The I²C protocol works as follows:

START: Data transmission on the bus begins with a high to low transition on the SDA line while

SCL is held high (start condition (S) indicated by I²C bus master). Once the START signal is

transferred by the master, the bus is considered busy.

STOP: Each data transfer should be terminated by a Stop signal (P) generated by master. The

STOP condition is a low to HIGH transition on SDA line while SCL is held high.

ACK: Each byte of data transferred must be acknowledged. It is indicated by an acknowledge

bit sent by the receiver. The transmitter must release the SDA line (no pull down) during the

acknowledge pulse while the receiver must then pull the SDA line low so that it remains stable

low during the high period of the acknowledge clock cycle.

In the following diagrams these abbreviations are used:

S Start

P Stop

ACKS Acknowledge by slave

ACKM Acknowledge by master

NACKM Not acknowledge by master

RW Read / Write

A START immediately followed by a STOP (without SCK toggling from logic “1” to logic “0”) is

not supported. If such a combination occurs, the STOP is not recognized by the device.

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I²C write access:

I²C write access can be used to write a data byte in one sequence.

The sequence begins with start condition generated by the master, followed by 7 bits slave

address and a write bit (RW = 0). The slave sends an acknowledge bit (ACK = 0) and releases

the bus. Then the master sends the one byte register address. The slave again acknowledges

the transmission and waits for the 8 bits of data which shall be written to the specified register

address. After the slave acknowledges the data byte, the master generates a stop signal and

terminates the writing protocol.

Example of an I²C write access:

Start RW ACKS ACKS ACKS Stop

0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 X X X X X X X X

S

Slave Adress

Register adress (0x10)

Control byte

Data byte

Data (0x09)

P

Figure 19: I²C write

I²C read access:

I²C read access also can be used to read one or multiple data bytes in one sequence.

A read sequence consists of a one-byte I²C write phase followed by the I²C read phase. The

two parts of the transmission must be separated by a repeated start condition (Sr). The I²C write

phase addresses the slave and sends the register address to be read. After slave

acknowledges the transmission, the master generates again a start condition and sends the

slave address together with a read bit (RW = 1). Then the master releases the bus and waits for

the data bytes to be read out from slave. After each data byte the master has to generate an

acknowledge bit (ACK = 0) to enable further data transfer. A NACKM (ACK = 1) from the

master stops the data being transferred from the slave. The slave releases the bus so that the

master can generate a STOP condition and terminate the transmission.

The register address is automatically incremented and, therefore, more than one byte can be

sequentially read out. Once a new data read transmission starts, the start address will be set to

the register address specified in the latest I²C write command. By default the start address is

set at 0x00. In this way repetitive multi-bytes reads from the same starting address are possible.

In order to prevent the I²C slave of the device to lock-up the I²C bus, a watchdog timer (WDT) is

implemented. The WDT observes internal I²C signals and resets the I²C interface if the bus is

locked-up by the BMA255. The activity and the timer period of the WDT can be configured

through the bits (0x34) i2c_wdt_en and (0x34) i2c_wdt_sel.

Writing ´1´ (´0´) to (0x34) i2c_wdt_en activates (de-activates) the WDT. Writing ´0´ (´1´) to

(0x34) i2c_wdt_se selects a timer period of 1 ms (50 ms).

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Example of an I²C read access:

Start RW ACKS

dummy

ACKS

00110000 X0000010

Start RW ACKS ACKM

ACKM

0 0 1 1 0 0 0 1 X X X X X X X X X X X X X X X X …

ACKM

…XXXXXXXX XXXXXXXX …

ACKM NACK Stop

…XXXXXXXX XXXXXXXX

Sr

Slave Adress

Read Data (0x03)

Read Data (0x02)

Control byte

Data byte

S

Slave Adress

Register adress (0x02)

P

Data byte

Read Data (0x06)

Read Data (0x07)

Data byte

Read Data (0x04)

Read Data (0x05)

Figure 20: I²C multiple read

7.2.1 SPI and I²C Access Restrictions

In order to allow for the correct internal synchronisation of data written to the BMA255, certain

access restrictions apply for consecutive write accesses or a write/read sequence through the

SPI as well as I2C interface. The required waiting period depends on whether the device is

operating in normal mode (or standby mode, or low-power mode 2) or suspend mode (or low-

power mode 1).

As illustrated in figure 21, an interface idle time of at least 2 µs is required following a write

operation when the device operates in normal mode (or standby mode, or low-power mode 2).

In suspend mode (or low-power mode 1) an interface idle time of least 450 µs is required.

X-after-Write

Register Update Period

(> 2us / 450us)

Write-Operation X-Operation

Figure 21: Post-Write Access Timing Constraints

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8. Pin-out and connection diagram

8.1 Pin-out

Figure 22: Pin-out top view Figure 23: Pin-out bottom view

Table 24: Pin description

Pin#

Name

I/O Type

Description

Connect to

in SPI 4W

In SPI 3W

in I²C

1

SDO

Digital out

Serial data output in SPI

Address select in I²C mode

see chapter 7.2

SDO

DNC (float)

GND for default

addr.

2

SDx

Digital I/O

SDA serial data I/O in I²C

SDI serial data input in SPI

4W

SDA serial data I/O in SPI

3W

SDI

SDA

3

VDDIO

Supply

Digital I/O supply voltage

(1.2V … 3.6V)

VDDIO

4

NC

--

GND

5

INT1

Digital out

Interrupt output 1 *

INT1

6

INT2

Digital out

Interrupt output 2 *

INT2

7

VDD

Supply

Power supply for analog &

digital domain (1.62V …

3.6V)

VDD

8

GNDIO

Ground

Ground for I/O

GND

9

GND

Ground

Ground for digital & analog

GND

10

CSB

Digital in

Chip select for SPI mode

CSB

DNC (float)

11

PS

Digital in

Protocol select (GND = SPI,

VDDIO = I²C)

GND

VDDIO

12

SCx

Digital in

SCK for SPI serial clock

SCL for I²C serial clock

SCK

SCL

* If INT1 and/or INT2 are not used, please do not connect them (DNC).

Bottom View

Pads visible!

Top View

Pads not visible!

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8.2 Connection diagram 4-wire SPI

Figure 24: 4-wire SPI connection

Note: the recommended value for C1, C2 is 100 nF.

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8.3 Connection diagram 3-wire SPI

Figure 25: 3-wire SPI connection

Note: the recommended value for C1, C2 is 100 nF.

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8.4 Connection diagram I2C

Figure 26: I²C connection

Note: the recommended value for C1, C2 is 100 nF.

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9. Package

9.1 Outline dimensions

The sensor housing is a standard LGA package. Its dimensions are the following.

Figure 27: Package outline dimensions

Pin1 marking:

Metal pad internally connected to GND

(external connection not recommended)

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9.2 Sensing axes orientation

If the sensor is accelerated in the indicated directions, the corresponding channel will deliver a

positive acceleration signal (dynamic acceleration). If the sensor is at rest and the force of

gravity is acting along the indicated directions, the output of the corresponding channel will be

negative (static acceleration).

Example: If the sensor is at rest or at uniform motion in a gravity field according to the figure

given below, the output signals are:

• ± 0g for the X channel

• ± 0g for the Y channel

• + 1g for the Z channel

Figure 28: Orientation of sensing axis

The following table lists all corresponding output signals on X, Y, and Z while the sensor is at

rest or at uniform motion in a gravity field under assumption of a ±2g range setting and a top

down gravity vector as shown above.

Table 25: Output signals depending on sensor orientation

Sensor Orientation

(gravity vector )

Output Signal X

0g / 0LSB

1g / 1024LSB

0g / 0LSB

-1g / -1024LSB

0g / 0LSB

Output Signal Y

-1g / -1024LSB

0g / 0LSB

1g / 1024LSB

0g / 0LSB

Output Signal Z

0g / 0LSB

1g / 1024LSB

-1g / -1024LSB

upright

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9.3 Landing Pattern Recommendation

For the design of the landing patterns, we recommend the following dimensioning:

Figure 29: Landing patterns; dimensions are in mm

Same tolerances as given for the outline dimensions (Chapter 9.1, Figure 27) should be

assumed.

A wiring no-go area in the top layer of the PCB below the sensor is strongly recommended (e.g.

no vias, wires or other metal structures).

BMA255

Data sheet

Page 112

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.

9.4 Marking

9.4.1 Mass production samples

Table 26: Marking of mass production samples

Labeling

Name

Symbol

Remark



Lot counter

CCC

3 alphanumeric digits, variable

to generate mass production trace-code

Product number

T

1 alphanumeric digit, fixed

to identify product type, T = “K”

Sub-con ID

L

1 alphanumeric digit, variable

to identify sub-con

Pin 1 identifier

•

--

9.4.2 Engineering samples

Table 27: Marking of engineering samples

Labeling

Name

Symbol

Remark



Eng. sample ID

N

1 alphanumeric digit, fixed to identify

engineering sample, N = “ * ” or “e” or “E”

Sample ID

XX

2 alphanumeric digits, variable

to generate trace-code.

Counter ID

CC

2 alphanumeric digits, variable

to generate trace-code

Pin 1 identifier

•

--

XXN

CC

CCC

TL

BMA255

Data sheet

Page 113

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.

9.5 Soldering guidelines

The moisture sensitivity level of the BMA255 sensors corresponds to JEDEC Level 1, see also

- IPC/JEDEC J-STD-020C "Joint Industry Standard: Moisture/Reflow Sensitivity

Classification for non-hermetic Solid State Surface Mount Devices"

- IPC/JEDEC J-STD-033A "Joint Industry Standard: Handling, Packing, Shipping and Use of

Moisture/Reflow Sensitive Surface Mount Devices"

The sensor fulfils the lead-free soldering requirements of the above-mentioned IPC/JEDEC

standard, i.e. reflow soldering with a peak temperature up to 260°C.

Figure 30: Soldering profile

BMA255

Data sheet

Page 114

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.

9.6 Handling instructions

Micromechanical sensors are designed to sense acceleration with high accuracy even at low

amplitudes and contain highly sensitive structures inside the sensor element. The MEMS

sensor can tolerate mechanical shocks up to several thousand g's. However, these limits might

be exceeded in conditions with extreme shock loads such as e.g. hammer blow on or next to

the sensor, dropping of the sensor onto hard surfaces etc.

We recommend to avoid g-forces beyond the specified limits during transport, handling and

mounting of the sensors in a defined and qualified installation process.

This device has built-in protections against high electrostatic discharges or electric fields (e.g.

2kV HBM); however, anti-static precautions should be taken as for any other CMOS

component. Unless otherwise specified, proper operation can only occur when all terminal

voltages are kept within the supply voltage range. Unused inputs must always be tied to a

defined logic voltage level.

BMA255

Data sheet

Page 115

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.

9.7 Tape and reel specification

The BMA255 is shipped in a standard cardboard box.

The box dimension for 1 reel is: L x W x H = 35cm x 35cm x 6cm.

BMA255 quantity: 10,000pcs per reel, please handle with care.

Figure 31: Tape and reel dimensions in mm

BMA255

Data sheet

Page 116

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.

9.7.1 Orientation within the reel

 Processing direction 

Figure 32: Orientation of the BMA255 devices relative to the tape

BMA255

Data sheet

Page 117

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.

9.8 Environmental safety

The BMA255 sensor meets the requirements of the EC restriction of hazardous substances

(RoHS) directive, see also:

Directive 2002/95/EC of the European Parliament and of the Council of 8 September

2011 on the restriction of the use of certain hazardous substances in electrical and

electronic equipment.

9.8.1 Halogen content

The BMA255 is halogen-free. For more details on the analysis results please contact your

Bosch Sensortec representative.

9.8.2 Internal package structure

Within the scope of Bosch Sensortec’s ambition to improve its products and secure the mass

product supply, Bosch Sensortec qualifies additional sources (e.g. 2nd source) for the LGA

package of the BMA255.

While Bosch Sensortec took care that all of the technical packages parameters are described

above are 100% identical for all sources, there can be differences in the chemical content and

the internal structural between the different package sources.

However, as secured by the extensive product qualification process of Bosch Sensortec, this

has no impact to the usage or to the quality of the BMA255 product.

BMA255

Data sheet

Page 118

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.

10. Legal disclaimer

10.1 Engineering samples

Engineering Samples are marked with an asterisk (*) or (e) or (E). Samples may vary from the

valid technical specifications of the product series contained in this data sheet. They are

therefore not intended or fit for resale to third parties or for use in end products. Their sole

purpose is internal client testing. The testing of an engineering sample may in no way replace

the testing of a product series. Bosch Sensortec assumes no liability for the use of engineering

samples. The Purchaser shall indemnify Bosch Sensortec from all claims arising from the use of

engineering samples.

10.2 Product use

Bosch Sensortec products are developed for the consumer goods industry. They may only be

used within the parameters of this product data sheet. They are not fit for use in life-sustaining

or security sensitive systems. Security sensitive systems are those for which a malfunction is

expected to lead to bodily harm or significant property damage. In addition, they are not fit for

use in products which interact with motor vehicle systems.

The resale and/or use of products are at the purchaser’s own risk and his own responsibility.

The examination of fitness for the intended use is the sole responsibility of the Purchaser.

The purchaser shall indemnify Bosch Sensortec from all third party claims arising from any

product use not covered by the parameters of this product data sheet or not approved by Bosch

Sensortec and reimburse Bosch Sensortec for all costs in connection with such claims.

The purchaser must monitor the market for the purchased products, particularly with regard to

product safety, and inform Bosch Sensortec without delay of all security relevant incidents.

10.3 Application examples and hints

With respect to any examples or hints given herein, any typical values stated herein and/or any

information regarding the application of the device, Bosch Sensortec hereby disclaims any and

all warranties and liabilities of any kind, including without limitation warranties of non-

infringement of intellectual property rights or copyrights of any third party. The information given

in this document shall in no event be regarded as a guarantee of conditions or characteristics.

They are provided for illustrative purposes only and no evaluation regarding infringement of

intellectual property rights or copyrights or regarding functionality, performance or error has

been made.

BMA255

Data sheet

Page 119

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.

11. Document history and modification

Rev. No

Chapter

Description of modification/changes

Date

0.1

Initial internal release

01 June 2012

0.2

Internal revision, not for release

0.3

Internal revision, not for release

0.4

Internal revision, not for release

0.5

All

Initial external release

01 August 2012

0.6

1, 4.1, 4.2,

6.2, 7.1,

9.3

Update

24 Sep 2012

0.7

4.5.2,

4.7.8, 6.2,

9.1, 9.3

Update

22 Oct 2012

1.0

1, 4.2,

4.7.3,

4.7.7, 6.2,

9.3, 9.4.1,

9.8

Update

21 May 2013

1.1

4.7

Update Single tap; update high-g interrupt

12.12.13

6.2

Update 0x0F; update 0x2B; update 0x32

1.2

4.2

sleeptimer_en->sleeptimer_mode, linguistic

improvement: “… a wake-up time of at least …

01 August 2014

4.5.1

Slow compensation update (High-pass filter cut

off frequency)

4.7.6

Tap sensing update (temporary latched interrupt)

6.2

0x37 cut_of update

7.2

I²C description update

Bosch Sensortec GmbH

Gerhard-Kindler-Strasse 8

72770 Reutlingen / Germany

contact@bosch-sensortec.com

www.bosch-sensortec.com

Modifications reserved | Printed in Germany

Specifications subject to change without notice

Document number: BST-BMA255-DS004-05

Revision_1.2_August 2014

Mouser Electronics

Authorized Distributor

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