Final data sheet

BME280Combined humidity and pressure sensor
Bosch Sensortec

BME280: Final data sheet
Document revision

1.0

Document release dateNovember 11 , 2014

Document number

BST-BME280-DS001-09

Technical reference code(s)0 273 141 185

Notes

th

Data in this document are subject to change without notice. Productphotos and pictures are for illustration purposes only and may differ fromthe real product’s appearance.

Final Datasheet
BME280 Environmental sensor

Page 2

BME280
DIGITAL HUMIDITY, PRESSURE AND TEMPERATURE SENSOR
Key features
 Package
 Digital interface
 Supply voltage







2.5 mm x 2.5 mm x 0.93 mm metal lid LGA
I²C (up to 3.4 MHz) and SPI (3 and 4 wire, up to 10 MHz)VDD main supply voltage range: 1.71 V to 3.6 V
VDDIO interface voltage range: 1.2 V to 3.6 V
Current consumption
1.8 µA @ 1 Hz humidity and temperature
2.8 µA @ 1 Hz pressure and temperature
3.6 µA @ 1 Hz humidity, pressure and temperature
0.1 µA in sleep mode
Operating range-40…+85 °C, 0…100 % rel. humidity, 300…1100 hPa
Humidity sensor and pressure sensor can be independently enabled / disabled
Register and performance compatible to Bosch Sensortec BMP280 digital pressure sensor
RoHS compliant, halogen-free, MSL1

Key parameters for humidity sensor
 Response time1s Accuracy tolerance±3 % relative humidity
 Hysteresis±1% relative humidity
Key parameters for pressure sensor
 RMS Noise
0.2 Pa, equiv. to 1.7 cm
 Offset temperature coefficient ±1.5 Pa/K, equiv. to ±12.6 cm at 1 °C temperature change
Typical application
 Context awareness, e.g. skin detection, room change detection
 Health monitoring / well-being
 Warning regarding dehydration or heat stroke
 Spirometry (measurement of lung volume and air flow) Home automation control
 control heating, venting, air conditioning (HVAC)
 Internet of things GPS enhancement (e.g. time-to-first-fix improvement, dead reckoning, slope detection)
 Indoor navigation (change of floor detection, elevator detection)
 Outdoor navigation, leisure and sports applications
 Weather forecast
 Vertical velocity indication (rise/sink speed)
Target devices
 Handsets such as mobile phones, tablet PCs, GPS devices
 Navigation systems and gaming, e.g flying toys
 Camera (DSC, video) and portable health care devices
 Home weather stations, flying toys and smart watches

BST-BME280-DS001-09 | Revision 1.0 | November 2014

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

Final Datasheet
BME280 Environmental sensor

Page 3General Description
The BME280 is as combined digital humidity, pressure and temperature sensor based on
proven sensing principles. The sensor module is housed in an extremely compact metal-lid LGA
package with a footprint of only 2.5 × 2.5 mm² with a height of 0.93 mm. Its small dimensions
and its low power consumption allow the implementation in battery driven devices such as
handsets, GPS modules or watches. The BME280 is register and performance compatible to
the Bosch Sensortec BMP280 digital pressure sensor (see chapter 5.2 for details).
The BME280 achieves high performance in all applications requiring humidity and pressure
measurement. These emerging applications of home automation control, in-door navigation,
health care as well as GPS refinement require a high accuracy and a low TCO at the sametime.
The humidity sensor provides an extremely fast response time for fast context awarenessapplications and high overall accuracy over a wide temperature range.
The pressure sensor is an absolute barometric pressure sensor with extremely high accuracy
and resolution and drastically lower noise than the Bosch Sensortec BMP180.
The integrated temperature sensor has been optimized for lowest noise and highest resolution.
Its output is used for temperature compensation of the pressure and humidity sensors and canalso be used for estimation of the ambient temperature.
The sensor provides both SPI and I²C interfaces and can be supplied using 1.71 to 3.6 V for thesensor supply VDD and 1.2 to 3.6 V for the interface supply VDDIO. Measurements can betriggered by the host or performed in regular intervals. When the sensor is disabled, current
consumption drops to 0.1 µA.
BME280 can be operated in three power modes (see chapter 3.3):

sleep mode
normal mode
forced mode

In order to tailor data rate, noise, response time and current consumption to the needs of theuser, a variety of oversampling modes, filter modes and data rates can be selected.
Please contact your regional Bosch Sensortec partner for more information about software
packages.

BST-BME280-DS001-09 | Revision 1.0 | November 2014

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

Final Datasheet
BME280 Environmental sensor

Page 4

Index of Contents
1. SPECIFICATION ........................................................................................................................ 7
1.1 GENERAL ELECTRICAL SPECIFICATION .................................................................................. 7
1.2 HUMIDITY PARAMETER SPECIFICATION ................................................................................. 8
1.3 PRESSURE SENSOR SPECIFICATION ..................................................................................... 9
1.4 TEMPERATURE SENSOR SPECIFICATION ............................................................................. 10
2. ABSOLUTE MAXIMUM RATINGS .......................................................................................... 11
3. FUNCTIONAL DESCRIPTION ................................................................................................. 11
3.1 BLOCK DIAGRAM ............................................................................................................... 11
3.2 POWER MANAGEMENT ....................................................................................................... 12
3.3 SENSOR MODES................................................................................................................ 123.3.1 SENSOR MODE TRANSITIONS ......................................................................................................... 12
3.3.2 SLEEP MODE ................................................................................................................................. 13
3.3.3 FORCED MODE .............................................................................................................................. 13
3.3.4 NORMAL MODE.............................................................................................................................. 14

3.4 MEASUREMENT FLOW ....................................................................................................... 14
3.4.1 HUMIDITY MEASUREMENT .............................................................................................................. 15
3.4.2 PRESSURE MEASUREMENT ............................................................................................................ 15
3.4.3 TEMPERATURE MEASUREMENT ...................................................................................................... 15
3.4.4 IIR FILTER..................................................................................................................................... 16

3.5 RECOMMENDED MODES OF OPERATION .............................................................................. 17
3.5.1 WEATHER MONITORING ................................................................................................................. 17
3.5.2 HUMIDITY SENSING ........................................................................................................................ 18
3.5.3 INDOOR NAVIGATION...................................................................................................................... 18
3.5.4 GAMING ........................................................................................................................................ 19

3.6 NOISE .............................................................................................................................. 19
4. DATA READOUT ..................................................................................................................... 21
4.1 DATA REGISTER SHADOWING ............................................................................................. 21
4.2 OUTPUT COMPENSATION ................................................................................................... 21
4.2.1 COMPUTATIONAL REQUIREMENTS .................................................................................................. 22
4.2.2 TRIMMING PARAMETER READOUT ................................................................................................... 22
4.2.3 COMPENSATION FORMULAS ........................................................................................................... 23

5. GLOBAL MEMORY MAP AND REGISTER DESCRIPTION .................................................. 25
5.1 GENERAL REMARKS .......................................................................................................... 25
5.2 REGISTER COMPATIBILITY TO BMP280 .............................................................................. 25
5.3 MEMORY MAP ................................................................................................................... 25
5.4 REGISTER DESCRIPTION .................................................................................................... 26

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

Final Datasheet
BME280 Environmental sensor

Page 55.4.1 REGISTER 0XD0 “ID” ..................................................................................................................... 26
5.4.2 REGISTER 0XE0 “RESET”............................................................................................................... 26
5.4.3 REGISTER 0XF2 “CTRL_HUM” ........................................................................................................ 26
5.4.4 REGISTER 0XF3 “STATUS” ............................................................................................................. 26
5.4.5 REGISTER 0XF4 “CTRL_MEAS”....................................................................................................... 27
5.4.6 REGISTER 0XF5 “CONFIG” ............................................................................................................. 28
5.4.7 REGISTER 0XF7…0XF9 “PRESS” (_MSB, _LSB, _XLSB) ................................................................... 29
5.4.8 REGISTER 0XFA…0XFC “TEMP” (_MSB, _LSB, _XLSB).................................................................... 29
5.4.9 REGISTER 0XFD…0XFE “HUM” (_MSB, _LSB) ................................................................................ 30

6. DIGITAL INTERFACES ............................................................................................................ 31
6.1 INTERFACE SELECTION ...................................................................................................... 31
6.2 I²C INTERFACE.................................................................................................................. 31
6.2.1 I²C WRITE ..................................................................................................................................... 32
6.2.2 I²C READ ...................................................................................................................................... 33

6.3 SPI INTERFACE ................................................................................................................. 33
6.3.1 SPI WRITE .................................................................................................................................... 34
6.3.2 SPI READ ..................................................................................................................................... 34

6.4 INTERFACE PARAMETER SPECIFICATION ............................................................................. 35
6.4.1 GENERAL INTERFACE PARAMETERS................................................................................................ 35
6.4.2 I²C TIMINGS .................................................................................................................................. 35
6.4.3 SPI TIMINGS ................................................................................................................................. 36

7. PIN-OUT AND CONNECTION DIAGRAM............................................................................... 38
7.1 PIN-OUT ........................................................................................................................... 38
7.2 CONNECTION DIAGRAM I2C ................................................................................................ 39
7.3 CONNECTION DIAGRAM 4-WIRE SPI ................................................................................... 40
7.4 CONNECTION DIAGRAM 3-WIRE SPI ................................................................................... 41
7.5 PACKAGE DIMENSIONS ...................................................................................................... 42
7.6 LANDING PATTERN RECOMMENDATION ............................................................................... 43
7.7 MARKING.......................................................................................................................... 44
7.7.1 MASS PRODUCTION DEVICES ......................................................................................................... 44
7.7.2 ENGINEERING SAMPLES ................................................................................................................. 45

7.8 SOLDERING GUIDELINES AND RECONDITIONING RECOMMENDATIONS .................................... 46
7.9 RECONDITIONING PROCEDURE .......................................................................................... 47
7.10 TAPE AND REEL SPECIFICATION........................................................................................ 47
7.10.1 DIMENSIONS ............................................................................................................................... 47
7.10.2 ORIENTATION WITHIN THE REEL.................................................................................................... 48

7.11 MOUNTING AND ASSEMBLY RECOMMENDATIONS ............................................................... 49
7.12 ENVIRONMENTAL SAFETY ................................................................................................ 49
7.12.1 ROHS ........................................................................................................................................ 49
7.12.2 HALOGEN CONTENT .................................................................................................................... 49
7.12.3 INTERNAL PACKAGE STRUCTURE .................................................................................................. 49

BST-BME280-DS001-09 | Revision 1.0 | November 2014

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

Final Datasheet
BME280 Environmental sensor

Page 6

8. APPENDIX A: ALTERNATIVE COMPENSATION FORMULAS ............................................ 50
8.1 COMPENSATION FORMULAS IN DOUBLE PRECISION FLOATING POINT ..................................... 50
8.2 PRESSURE COMPENSATION IN 32 BIT FIXED POINT .............................................................. 51
9. APPENDIX B: MEASUREMENT TIME AND CURRENT CALCULATION ............................ 52
9.1 MEASUREMENT TIME ......................................................................................................... 52
9.2 MEASUREMENT RATE IN FORCED MODE .............................................................................. 52
9.3 MEASUREMENT RATE IN NORMAL MODE .............................................................................. 52
9.4 RESPONSE TIME USING IIR FILTER ..................................................................................... 53
9.5 CURRENT CONSUMPTION................................................................................................... 53
10. LEGAL DISCLAIMER............................................................................................................. 54
10.1 ENGINEERING SAMPLES................................................................................................... 54
10.2 PRODUCT USE ................................................................................................................ 54
10.3 APPLICATION EXAMPLES AND HINTS ................................................................................. 54
10.4 HANDLING INSTRUCTIONS................................................................................................ 54
11. DOCUMENT HISTORY AND MODIFICATION ..................................................................... 55

BST-BME280-DS001-09 | Revision 1.0 | November 2014

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

Final Datasheet
BME280 Environmental sensor

Page 7

1. Specification
If not stated otherwise, All values are valid over the full voltage range
 All minimum/maximum values are given for the full accuracy temperature range
 Minimum/maximum values of drifts, offsets and temperature coefficients are ±3 values
over lifetime
 Typical values of currents and state machine timings are determined at 25 °C
 Minimum/maximum values of currents are determined using corner lots over complete
temperature range
 Minimum/maximum values of state machine timings are determined using corner lots
over 0…+65 °C temperature range
The specification tables are split into humidity, pressure, and temperature part of BME280.

1.1 General electrical specification
Table 1: Electrical parameter specification
Parameter

SymbolCondition

Min

Typ

Max

Unit

VDD

ripple max. 50 mVpp

1.71

1.8

3.6

V

1.2

1.8

3.6

V

Supply Voltage
Internal Domains
Supply Voltage
I/O Domain

VDDIO

Sleep current

IDDSL

0.1

0.3

µA

Standby current(inactive period of
normal mode)

IDDSB

0.2

0.5

µA

Current duringhumidity
measurement

IDDH

Max value at 85 °C

340

µA

Current during
pressuremeasurement

IDDP

Max value at -40 °C

714

µA

Current during
temperature
measurement

IDDT

Max value at 85 °C

350

µA

Start-up time

tstartupTime to firstcommunication after
both VDD > 1.58 V
and VDDIO > 0.65 V

2ms

Power supply
rejection ratio (DC)

PSRR

full VDD range

±0.01
±5

%RH/V
Pa/V

Standby time
accuracy

Δtstandby±25%

BST-BME280-DS001-09 | Revision 1.0 | November 2014±5

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

Final Datasheet
BME280 Environmental sensor

Page 8

1.2 Humidity parameter specification
Table 2: Humidity parameter specification
Parameter

SymbolCondition

Min

Typ

Max

Unit

For temperatures< 0 °C and > 60 °C
see Figure 1

-40

25

85

°C

RH

100

%RH

Supply current

IDD,H

1 Hz forced mode,
humidity andtemperature

1.8

2.8

µA

Absolute accuracy
tolerance

AH

20…80 %RH,
25 °C, including
hysteresis

±3

%RH

HH

109010 %RH,
25 °C

±1

%RH

NLH

1090 %RH, 25 °C

1%RH

900 or 090 %RH,
25°C

1

s

0.008

%RH

Operating range

3

4Hysteresis

Nonlinearity

5

Response time to
6complete 63% of step0

Resolution

RH

Noise in humidity (RMS)

NH

Highest oversampling,see chapter 3.6

0.02

%RH

Long term stability

Hstab

10…90 %RH, 25 °C

0.5

%RH/
year

3

When exceeding the operating range (e.g. for soldering), humidity sensing performance is
temporarily degraded and reconditioning is recommended as described in section 7.8.
Operating range only for non-condensing environment.
4
For hysteresis measurement the sequence 103050709070503010 %RH isused. The hysteresis is defined as the difference between measurements of the humidity up /down branch and the averaged curve of both branches
5
Non-linear contributions to the sensor data are corrected during the calculation of the relative
humidity by the compensation formulas described in section 4.2.3.
6
The air-flow in direction to the vent-hole of the device has to be dimensioned in a way that asufficient air exchange inside to outside will be possible. To observe effects on the response
time-scale of the device an air-flow velocity of approx. 1 m/s is needed.

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

Final Datasheet
BME280 Environmental sensor

Page 9100

Relative humidity [%]

80

60

40

20

0
-40

-20

0

20
40
Temperature [°C]6080Figure 1: humidity sensor operating range

1.3 Pressure sensor specification
Table 3: Pressure parameter specification
Parameter

SymbolCondition

Min

Typ

Max

operational

-40

25

+85

full accuracy

0

+65

300

1100

hPa

4.2

µA

Operating temperature
range

TA

Operating pressure
range

P

full accuracy

Supply current

IDD,LP

1 Hz forced mode,pressure andtemperature, lowest
power

Temperature coefficient
9of offset

TCOP

25…65 °C, 900 hPa

AP,full

Arel

Absolute accuracypressure
Relative accuracypressure
VDD = 3.3V

2.8

Unit
°C

±1.5

Pa/K

±12.6

cm/K

300 . . . 1100 hPa
0 . . . 65 °C

±1.0

hPa

700 … 900hPa
25 . . . 40 °C

±0.12

hPa

9

When changing temperature by e.g. 10 °C at constant pressure / altitude, the measured
pressure / altitude will change by (10 × TCOP).

BST-BME280-DS001-09 | Revision 1.0 | November 2014

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

Final Datasheet
BME280 Environmental sensor
Resolution ofpressure output data

RP

Highest oversampling

0.18

Pa

Full bandwidth,
highest oversamplingSee chapter 3.6

1.3

Pa

NP,fullBW

11cm

Reduced bandwidth,
highest oversamplingSee chapter 3.6

0.2

Pa

NP,filtered

1.7

cm

Noise in pressure

Minimum solder height
50µm

Solder drift
Long term stability

10

Possible sampling rate

Page 10

Pstabper yearfsample_P

Lowest oversampling,see chapter 9.2

-0.5

157

+2.0

hPa

±1.0

hPa

182

Hz

1.4 Temperature sensor specification
Table 4: Pressure parameter specification
Parameter

SymbolCondition

Min

Typ

Max

Unit

Operational

-40

25

85

°C

Full accuracy

0

65

°C

Operating range

T

Supply current

IDD,T

1 Hz forced mode,temperature
measurement only

1.0

µA

AT,25

25 °C

±0.5

°C

AT,full

0…65 °C±1.0°COutput resolution

RT

API output resolution

0.01

°C

RMS noiseNT

Lowest oversampling

0.005

°C

Absolute accuracy
11
temperature

10

Long term stability is specified in the full accuracy operating pressure range 0 … 65 °C
Temperature measured by the internal temperature sensor. This temperature value depends
on the PCB temperature, sensor element self-heating and ambient temperature and is typicallyabove ambient temperature.
11

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

Final Datasheet
BME280 Environmental sensor

Page 11

2. Absolute maximum ratings
The absolute maximum ratings are determined over complete temperature range using cornerlots. The values are provided in Table 5.
Table 5: Absolute maximum ratings
Parameter
Voltage at any supply pin

Condition

Min

Max

Unit

VDD and VDDIO pin

-0.3

4.25

V

-0.3

VDDIO + 0.3

V

-45

+85

°C

0

20 000hPa

HBM, at any pin

±2

kV

CDM

±500

V

Machine model

±200

V

Voltage at any interface pin
Storage temperature≤ 65% RH

Pressure

ESD

Condensation

No power supplied

Allowed3. Functional description
3.1 Block diagram
Figure 2 shows a simplified block diagram of the BME280:
VDD

Pressuresensing
element

Pressure
front-end

Humidity
sensing
element

Humidity
front-end

Temperaturesensing
element

Temperature
front-end

Voltageregulator(analog &digital)VDDIO

Voltagereference

ADC
Logic

I
n
t
e
r
f
a
c
e

SDI

SDO

SCK

CSB

OSC POR NVM
GND

Figure 2: Block diagram of BME280

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BME280 Environmental sensor

Page 12

3.2 Power management
The BME280 has two distinct power supply pins
 VDD is the main power supply for all internal analog and digital functional blocks
 VDDIO is a separate power supply pin used for the supply of the digital interface
A power-on reset (POR) generator is built in; it resets the logic part and the register values after
both VDD and VDDIO reach their minimum levels. There are no limitations on slope and sequenceof raising the VDD and VDDIO levels. After powering up, the sensor settles in sleep mode
(described in chapter 3.3.2).
It is prohibited to keep any interface pin (SDI, SDO, SCK or CSB) at a logical high level when
VDDIO is switched off. Such a configuration can permanently damage the device due an
excessive current flow through the ESD protection diodes.
If VDDIO is supplied, but VDD is not, the interface pins are kept at a high-Z level. The bus cantherefore already be used freely before the BME280 VDD supply is established.
Resetting the sensor is possible by cycling VDD level or by writing a soft reset command. Cycling
the VDDIO level will not cause a reset.

3.3 Sensor modes
The BME280 offers three sensor modes: sleep mode, forced mode and normal mode. Thesecan be selected using the mode[1:0] setting (see chapter 5.4.5). The available modes are:

Sleep mode: no operation, all registers accessible, lowest power, selected after startup
Forced mode: perform one measurement, store results and return to sleep mode
Normal mode: perpetual cycling of measurements and inactive periods.

The modes will be explained in detail in chapters 3.3.2 (sleep mode), 3.3.3 (forced mode) and 0(normal mode).
3.3.1 Sensor mode transitions
The supported mode transitions are shown in Figure 3. If the device is currently performing ameasurement, execution of mode switching commands is delayed until the end of the currently
running measurement period. Further mode change commands or other write commands to theregister ctrl_hum are ignored until the mode change command has been executed. Modetransitions other than the ones shown below are tested for stability but do not represent
recommended use of the device.

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Final Datasheet
BME280 Environmental sensor

Page 13Power OFF(VDD or VDDIO = 0)
VDD and VDDIO
supplied

Sleep

Normal

00
:0] =
1
[
e
d
Mo
11
:0] =
1
[
e
d
Mo
Mode[1:0] = 01(cyclic standby andmeasurement periods)
Mode[1:0] = 01

Forced(one measurement
period)Figure 3: Sensor mode transition diagram
3.3.2 Sleep mode
Sleep mode is entered by default after power on reset. In sleep mode, no measurements are
performed and power consumption (IDDSM) is at a minimum. All registers are accessible; Chip-ID
and compensation coefficients can be read. There are no special restrictions on interface
timings.

current

3.3.3 Forced mode
In forced mode, a single measurement is performed in accordance to the selected
measurement and filter options. When the measurement is finished, the sensor returns to sleep
mode and the measurement results can be obtained from the data registers. For a next
measurement, forced mode needs to be selected again. This is similar to BMP180 operation.
Using forced mode is recommended for applications which require low sampling rate or hostbased synchronization. The timing diagram is shown below.

Write
POR settings

Mode[1:0] = 01

Data readout Mode[1:0] = 01

Measurement H

Measurement P

Measurement T

Measurement H

IDDSB
IDDSL

Measurement T

IDDP
IDDT
IDDH

Measurement P

cycle time = rate of force modetmeasuretime

Figure 4: Forced mode timing diagram

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BME280 Environmental sensor

Page 14current

3.3.4 Normal mode
Normal mode comprises an automated perpetual cycling between an (active) measurement
period and an (inactive) standby period.
The measurements are performed in accordance to the selected measurement and filter
options. The standby time is determined by the setting t_sb[2:0] and can be set to between 0.5
and 1000 ms according to Table 27.
The total cycle time depends on the sum of the active time (see chapter 9) and standby time
tstandby. The current in the standby period (IDDSB) is slightly higher than in sleep mode. Aftersetting the measurement and filter options and enabling normal mode, the last measurement
results can always be obtained at the data registers without the need of further write accesses.
Using normal mode is recommended when using the IIR filter. This is useful for applications inwhich short-term disturbances (e.g. blowing into the sensor) should be filtered. The timing
diagram is shown below:

Write
POR settings

Mode[1:0] = 11

Data readout
when needed

Measurement H

Measurement P

Measurement T

Measurement H

IDDSB
IDDSL

Measurement T

IDDP
IDDT
IDDH

Measurement P

cycle time = tmeasure + tstandby
tmeasure
tstandby

time

Figure 5: Normal mode timing diagram

3.4 Measurement flow
The BME280 measurement period consists of a temperature, pressure and humidity
measurement with selectable oversampling. After the measurement period, the pressure andtemperature data can be passed through an optional IIR filter, which removes short-term
fluctuations in pressure (e.g. caused by slamming a door). For humidity, such a filter is notneeded and has not been implemented. The flow is depicted in the diagram below.

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Start
measurement cycle

Measure temperature(oversampling set by osrs_t;
skip if osrs_t = 0)

IIR filter enabled?

No

Yes
Measure pressure(oversampling set by osrs_p;
skip if osrs_p = 0)

IIR filter initialised?

No

Copy ADC values
to filter memory(initalises IIR filter)

Yes
Measure humidity(oversampling set by osrs_h;
skip if osrs_h = 0)Update filter memory using
filter memory, ADC value
and filter coefficient

Copy filter memory
to output registersEnd
measurement cycle

Figure 6: BME280 measurement cycle
The individual blocks of the diagram above will be detailed in the following subchapters.
3.4.1 Humidity measurement
The humidity measurement can be enabled or skipped. When enabled, several oversampling
options exist. The humidity measurement is controlled by the osrs_h[2:0] setting, which isdetailed in chapter 5.4.3. For the humidity measurement, oversampling is possible to reduce thenoise. The resolution of the humidity measurement is fixed at 16 bit ADC output.
3.4.2 Pressure measurement
Pressure measurement can be enabled or skipped. When enabled, several oversampling
options exist. The pressure measurement is controlled by the osrs_p[2:0] setting which isdetailed in chapter 5.4.5. For the pressure measurement, oversampling is possible to reduce
the noise. The resolution of the pressure data depends on the IIR filter (see chapter 0) and theoversampling setting (see chapter 5.4.5):
 When the IIR filter is enabled, the pressure resolution is 20 bit.
 When the IIR filter is disabled, the pressure resolution is 16 + (osrs_p – 1) bit, e.g. 18 bit
when osrs_p is set to ‘3’.
3.4.3 Temperature measurement
Temperature measurement can be enabled or skipped. Skipping the measurement could be
useful to measure pressure extremely rapidly. When enabled, several oversampling options
exist. The temperature measurement is controlled by the osrs_t[2:0] setting which is detailed inchapter 5.4.5. For the temperature measurement, oversampling is possible to reduce the noise.
The resolution of the temperature data depends on the IIR filter (see chapter 0) and theoversampling setting (see chapter 5.4.5):
 When the IIR filter is enabled, the temperature resolution is 20 bit.
 When the IIR filter is disabled, the temperature resolution is 16 + (osrs_t – 1) bit, e.g. 18
bit when osrs_t is set to ‘3’.

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3.4.4 IIR filter
The humidity value inside the sensor does not fluctuate rapidly and does not require low passfiltering. However, the environmental pressure is subject to many short-term changes, caused
e.g. by slamming of a door or window, or wind blowing into the sensor. To suppress these
disturbances in the output data without causing additional interface traffic and processor workload, the BME280 features an internal IIR filter. It effectively reduces the bandwidth of thetemperature and pressure output signals12 and increases the resolution of the pressure andtemperature output data to 20 bit. The output of a next measurement step is filtered using thefollowing formula:

Data_filtered_old is the data coming from the current filter memory, and data_ADC is the data
coming from current ADC acquisition. Data_filtered is the new value of filter memory and thevalue that will be sent to the output registers.
The IIR filter can be configured to different filter coefficients, which slows down the response to
the sensor inputs. Note that the response time with enabled IIR filter depends on the number ofsamples generated, which means that the data output rate must be known to calculate theactual response time. For register configuration, please refer to Table 28. A sample responsetime calculation is shown in chapter 9.4.
Table 6: filter settings
Filter coefficient

Samples to reach ≥75 %of step response

Filter off

1

2

2

4

5

8

11

16

22

In order to find a suitable setting for filter, please consult chapter 3.5.
When writing to the register filter, the filter is reset. The next ADC values will the pass throughthe filter unchanged and become the initial memory values for the filter. If temperature orpressure measurements are skipped, the corresponding filter memory will be kept unchanged
even though the output registers are set to 0x80000. When the previously skipped
measurement is re-enabled, the output will be filtered using the filter memory from the last time
when the measurement was not skipped. If this is not desired, please write to the filter registerin order to re-initialize the filter.

12

Since the BME280 does not sample continuously, filtering can suffer from signals with afrequency higher than the sampling rate of the sensor. E.g. environmental fluctuations caused
by windows being opened and closed might have a frequency <5 Hz. Consequently, a sampling
rate of ODR = 10 Hz is sufficient to obey the Nyquist theorem.

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The step response (e.g. response to in sudden change in height) of the different filter settings is
displayed in Figure 7.
Step response at different IIR filter settings
100
90
80

Response to step [%]70
filter off
2
4
8
16

60
50
40
30
20
10
0

0

2

4

6

8

10 12 14 16 18 20 22 24 26 28 30
Number of samples

32

Figure 7: Step response at different IIR filter settings

3.5 Recommended modes of operation
The different oversampling options, filter settings and sensor modes result in a large number ofpossible settings. In this chapter, a number of settings recommended for various scenarios arepresented.
3.5.1 Weather monitoring
Description: Only a very low data rate is needed. Power consumption is minimal. Noise ofpressure values is of no concern. Humidity, pressure and temperature are monitored.
Table 7: Settings and performance for weather monitoring
Suggested settings for weather monitoring
Sensor mode
forced mode, 1 sample / minuteOversampling settings pressure ×1, temperature ×1, humidity ×1
IIR filter settings
filter off
Performance for suggested settings
Current consumption
0.16 µA
RMS Noise
3.3 Pa / 30 cm, 0.07 %RH
Data output rate
1/60 Hz

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3.5.2 Humidity sensing
Description: A low data rate is needed. Power consumption is minimal. Forced mode is used tominimize power consumption and to synchronize readout, but using normal mode would also be
possible.
Table 8: Settings and performance for humidity sensing
Suggested settings for weather monitoring
Sensor mode
forced mode, 1 sample / second
Oversampling settings pressure ×0, temperature ×1, humidity ×1
IIR filter settings
filter off
Performance for suggested settings
Current consumption
2.9 µARMS Noise
0.07 %RH
Data output rate
1 Hz

3.5.3 Indoor navigation
Lowest possible altitude noise is needed. A very low bandwidth is preferred. Increased power
consumption is tolerated. Humidity is measured to help detect room changes. This setting issuggested for the Android settings ‘SENSOR_DELAY_NORMAL’ and ‘SENSOR_DELAY_UI’.
Table 9: Settings and performance for indoor navigation
Suggested settings for indoor navigation
Sensor mode
normal mode, tstandby = 0.5 ms
Oversampling settings pressure ×16, temperature ×2, humidity ×1
IIR filter settings
filter coefficient 16
Performance for suggested settings
Current consumption
633 µARMS Noise
0.2 Pa / 1.7 cm
Data output rate
25Hz
Filter bandwidth
0.53 Hz
Response time (75%)
0.9 s

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3.5.4 Gaming
Low altitude noise is needed. The required bandwidth is ~2 Hz in order to respond quickly toaltitude changes (e.g. be able to dodge a flying monster in a game). Increased power
consumption is tolerated. Humidity sensor is disabled. This setting is suggested for the Android
settings ‘SENSOR_DELAY_GAMING’ and ‘SENSOR_DELAY_FASTEST’.
Table 10: Settings and performance for gaming
Suggested settings for gaming
Sensor mode
normal mode, tstandby = 0.5 ms
Oversampling settings pressure ×4, temperature ×1, humidity ×0
IIR filter settings
filter coefficient 16
Performance for suggested settings
Current consumption
581 µARMS Noise
0.3 Pa / 2.5 cm
Data output rate
83 Hz
Filter bandwidth
1.75 Hz
Response time (75%)
0.3 s

3.6 Noise
The noise depends on the oversampling and, for pressure and temperature, on the filter setting
used. The stated values were determined in a controlled environment and are based on the
average standard deviation of 32 consecutive measurement points taken at highest sampling
speed. This is needed in order to exclude long term drifts from the noise measurement. The
noise depends both on humidity/pressure oversampling and temperature oversampling, since
the temperature value is used for humidity/pressure temperature compensation. The
oversampling combinations use below results in an optimal power to noise ratio.
Table 11: Noise and current for humidity
Humidity / temperature
oversampling setting

Typical RMS noise inhumidity [%RH] at 25 °C

Typ. current [µA] at 1 Hz forced
mode, 25 °C, humidity andtemperature measurement, incl.
IDDSM

×1 / ×1

0.07

1.8

×2 / ×1

0.05

2.5

×4 / ×1

0.04

3.8

×8 / ×1

0.03

6.5

×16 / ×1

0.02

11.7

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Table 12: Noise and current for pressure
Typical RMS noise in pressure [Pa] at 25 °C
Pressure / temperature
oversampling setting

off

2

4

8

16

Typ. current [µA] at 1 Hz
forced mode, 25 °C,
pressure and temperature
measurement, incl. IDDSM

×1 / ×1

3.3

1.9

1.2

0.9

0.4

2.8

×2 / ×1

2.6

1.5

1.0

0.6

0.4

4.2

×4 / ×1

2.1

1.2

0.8

0.5

0.3

7.1

×8 / ×1

1.6

1.0

0.6

0.4

0.2

12.8

×16 / ×2

1.3

0.8

0.5

0.4

0.2

24.9

IIR filter coefficient

Table 13: Temperature dependence of pressure noise
RMS noise at different temperatures
Temperature

Typical change in noisecompared to 25 °C-10 °C

+25 %

25 °C

±0 %

75 °C

-5 %

Table 14: Noise in temperature
Temperature
oversampling setting

Typical RMS noise intemperature [°C] at 25 °C

×1

0.005

×2

0.004

×4

0.003

×8

0.003

×16

0.002

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4. Data readout
To read out data after a conversion, it is strongly recommended to use a burst read and not
address every register individually. This will prevent a possible mix-up of bytes belonging todifferent measurements and reduce interface traffic. Note that in I²C mode, even when pressure
was not measured, reading the unused registers is faster than reading temperature andhumidity data separately.
Data readout is done by starting a burst read from 0xF7 to 0xFC (temperature and pressure) orfrom 0xF7 to 0xFE (temperature, pressure and humidity). The data are read out in an unsigned
20-bit format both for pressure and for temperature and in an unsigned 16-bit format forhumidity. It is strongly recommended to use the BME280 API, available from Bosch Sensortec,
for readout and compensation. For details on memory map and interfaces, please consult
chapters 0 and 6 respectively.
After the uncompensated values for pressure, temperature and humidity ‘ut’, ‘up’ and ‘uh’ havebeen read, the actual humidity, pressure and temperature needs to be calculated using thecompensation parameters stored in the device. The procedure is elaborated in chapter 4.2.

4.1 Data register shadowing
In normal mode, the timing of measurements is not necessarily synchronized to the readout by
the user. This means that new measurement results may become available while the user isreading the results from the previous measurement. In this case, shadowing is performed inorder to guarantee data consistency. Shadowing will only work if all data registers are read in asingle burst read. Therefore, the user must use burst reads if he does not synchronize data
readout with the measurement cycle. Using several independent read commands may result ininconsistent data.
If a new measurement is finished and the data registers are still being read, the newmeasurement results are transferred into shadow data registers. The content of shadow
registers is transferred into data registers as soon as the user ends the burst read, even if not alldata registers were read.
The end of the burst read is marked by the rising edge of CSB pin in SPI case or by therecognition of a stop condition in I2C case. After the end of the burst read, all user data registers
are updated at once.

4.2 Output compensation
The BME280 output consists of the ADC output values. However, each sensing element
behaves differently. Therefore, the actual pressure and temperature must be calculated using a
set of calibration parameters. In this chapter, the method to read out the trimming values will begiven. The recommended calculation uses fixed point arithmetic and is given in chapter 4.2.3.
In high-level languages like Matlab™ or LabVIEW™, fixed-point code may not be well
supported. In this case the floating-point code in appendix 8.1 can be used as an alternative.
For 8-bit micro controllers, the variable size may be limited. In this case a simplified 32 bit
integer code with reduced accuracy is given in appendix 8.2.

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Page 224.2.1 Computational requirements
In the table below an overview is given for the number of clock cycles needed for compensation
on a 32 bit Cortex-M3 micro controller with GCC optimization level -O2. This controller does notfeature a floating point unit, thus all floating-point calculations are emulated. Floating point isonly recommended for PC application, where an FPU is present and these calculations are
performed drastically faster.
Table 15: Computational requirements for compensation formulas
Number of clocks (ARM Cortex-M3)
Compensation of

32 bitinteger

64 bitinteger

Doubleprecision

Humidity

~83

–

~2900

13

Temperature

~46

–

~2400

13

Pressure

~112

~1400

~5400

13

14

4.2.2 Trimming parameter readout
The trimming parameters are programmed into the devices’ non-volatile memory (NVM) during
production and cannot be altered by the customer. Each compensation word is a 16-bit signed
or unsigned integer value stored in two’s complement. As the memory is organized into 8-bit
words, two words must always be combined in order to represent the compensation word. The
8-bit registers are named calib00…calib41 and are stored at memory addresses 0x88…0xA1
and 0xE1…0xE7. The corresponding compensation words are named dig_T# for temperaturecompensation related values, dig_P# for pressure related values and dig_H# for humidity
related values. The mapping is seen in Table 16.
Table 16: Compensation parameter storage, naming and data type13
14

Register Address

Register content

Data type0x88 / 0x89

dig_T1 [7:0] / [15:8]

unsigned short

0x8A / 0x8B

dig_T2 [7:0] / [15:8]

signed short

0x8C / 0x8D

dig_T3 [7:0] / [15:8]

signed short

0x8E / 0x8F

dig_P1 [7:0] / [15:8]

unsigned short

0x90 / 0x91

dig_P2 [7:0] / [15:8]

signed short

0x92 / 0x93

dig_P3 [7:0] / [15:8]

signed short

0x94 / 0x95

dig_P4 [7:0] / [15:8]

signed short

0x96 / 0x97

dig_P5 [7:0] / [15:8]

signed short

0x98 / 0x99

dig_P6 [7:0] / [15:8]

signed short

0x9A / 0x9B

dig_P7 [7:0] / [15:8]

signed short

Use only recommended for high-level programming languages like Matlab™ or LabVIEW™
Use only recommended for 8-bit micro controllers

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0x9C / 0x9D

dig_P8 [7:0] / [15:8]

signed short

0x9E / 0x9F

dig_P9 [7:0] / [15:8]

signed short

0xA1

dig_H1 [7:0]

unsigned char

0xE1 / 0xE2

dig_H2 [7:0] / [15:8]

signed short

0xE3

dig_H3 [7:0]

unsigned char

0xE4 / 0xE5[3:0]

dig_H4 [11:4] / [3:0]signed short

0xE5[7:4] / 0xE6

dig_H5 [3:0] / [11:4]

signed short

0xE7

dig_H6signed char

4.2.3 Compensation formulas
Please note that it is strongly advised to use the API available from Bosch Sensortec to perform
readout and compensation. If this is not wanted, the code below can be applied at the user’srisk. Both pressure and temperature values are expected to be received in 20 bit format,
positive, stored in a 32 bit signed integer. Humidity is expected to be received in 16 bit format,
positive, stored in a 32 bit signed integer.
The variable t_fine (signed 32 bit) carries a fine resolution temperature value over to thepressure and humidity compensation formula and could be implemented as a global variable.
The data type “BME280_S32_t” should define a 32 bit signed integer variable type and canusually be defined as “long signed int”.
The data type “BME280_U32_t” should define a 32 bit unsigned integer variable type and canusually be defined as “long unsigned int”.
For best possible calculation accuracy in pressure, 64 bit integer support is needed. If this is notpossible on your platform, please see appendix 8.2 for a 32 bit alternative.
The data type “BME280_S64_t” should define a 64 bit signed integer variable type, which on
most supporting platforms can be defined as “long long signed int”. The revision of the code isrev.1.1.
// Returns temperature in DegC, resolution is 0.01 DegC. Output value of “5123” equals 51.23 DegC.
// t_fine carries fine temperature as global value
BME280_S32_t t_fine;
BME280_S32_t BME280_compensate_T_int32(BME280_S32_t adc_T){
BME280_S32_t var1, var2, T;
var1 = ((((adc_T>>3) – ((BME280_S32_t)dig_T1<<1))) * ((BME280_S32_t)dig_T2)) >> 11;
var2 = (((((adc_T>>4) – ((BME280_S32_t)dig_T1)) * ((adc_T>>4) – ((BME280_S32_t)dig_T1))) >> 12) *((BME280_S32_t)dig_T3)) >> 14;
t_fine = var1 + var2;
T = (t_fine * 5 + 128) >> 8;
return T;}// Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24 integer bits and 8 fractional bits).
// Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa
BME280_U32_t BME280_compensate_P_int64(BME280_S32_t adc_P){
BME280_S64_t var1, var2, p;
var1 = ((BME280_S64_t)t_fine) – 128000;
var2 = var1 * var1 * (BME280_S64_t)dig_P6;
var2 = var2 + ((var1*(BME280_S64_t)dig_P5)<<17);var2 = var2 + (((BME280_S64_t)dig_P4)<<35);
var1 = ((var1 * var1 * (BME280_S64_t)dig_P3)>>8) + ((var1 * (BME280_S64_t)dig_P2)<<12);
var1 = (((((BME280_S64_t)1)<<47)+var1))*((BME280_S64_t)dig_P1)>>33;
if (var1 == 0){
return 0; // avoid exception caused by division by zero}p = 1048576-adc_P;
p = (((p<<31)-var2)*3125)/var1;
var1 = (((BME280_S64_t)dig_P9) * (p>>13) * (p>>13)) >> 25;
var2 = (((BME280_S64_t)dig_P8) * p) >> 19;

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p = ((p + var1 + var2) >> 8) + (((BME280_S64_t)dig_P7)<<4);
return (BME280_U32_t)p;}// Returns humidity in %RH as unsigned 32 bit integer in Q22.10 format (22 integer and 10 fractional bits).
// Output value of “47445” represents 47445/1024 = 46.333 %RH
BME280_U32_t bme280_compensate_H_int32(BME280_S32_t adc_H){
BME280_S32_t v_x1_u32r;
v_x1_u32r = (t_fine – ((BME280_S32_t)76800));
v_x1_u32r = (((((adc_H << 14) – (((BME280_S32_t)dig_H4) << 20) – (((BME280_S32_t)dig_H5) * v_x1_u32r)) +((BME280_S32_t)16384)) >> 15) * (((((((v_x1_u32r * ((BME280_S32_t)dig_H6)) >> 10) * (((v_x1_u32r *((BME280_S32_t)dig_H3)) >> 11) + ((BME280_S32_t)32768))) >> 10) + ((BME280_S32_t)2097152)) *((BME280_S32_t)dig_H2) + 8192) >> 14));v_x1_u32r = (v_x1_u32r – (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((BME280_S32_t)dig_H1)) >> 4));
v_x1_u32r = (v_x1_u32r < 0 ? 0 : v_x1_u32r);
v_x1_u32r = (v_x1_u32r > 419430400 ? 419430400 : v_x1_u32r);
return (BME280_U32_t)(v_x1_u32r>>12);}

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5. Global memory map and register description
5.1 General remarks
The entire communication with the device is performed by reading from and writing to registers.
Registers have a width of 8 bits. There are several registers which are reserved; they should not
be written to and no specific value is guaranteed when they are read. For details on theinterface, consult chapter 6.

5.2 Register compatibility to BMP280
The BME280 is downward register compatible to the BMP280, which means that the pressure
and temperature control and readout is identical to BMP280. However, the following exceptions
have to be considered:
Table 17: Register incompatibilities between BMP280 and BME280
Register

Bits

Content

BMP280

BME280

0xD0 “id”

7:0

chip_id

0xF5 “config”

7:5

t_sb

0xF7…0xF9 “press”

19:0

press

Resolution (16…20 bit)depends only on osrs_p

0xFA…0xFC “temp”

19:0

temp

Resolution (16…20 bit)only depends on osrs_t

Read value is0x56 / 0x57 (samples)
0x58 (mass production)‘110’: 2000 ms‘111’: 4000 ms

Read value is 0x60
‘110’: 10 ms‘111’: 20 ms
Without filter, resolution depends on
osrs_p; when using filter, resolutionis always 20 bit
Without filter, resolution depends on
osrs_t; when using filter, resolution isalways 20 bit

5.3 Memory map
The memory map is given in Table 18 below. Reserved registers are not shown.
Table 18: Memory map
Register Name

Address

hum_lsb
hum_msb
temp_xlsb
temp_lsb
temp_msb
press_xlsb
press_lsb
press_msb
config
ctrl_meas
statusctrl_humcalib26..calib41
reset
id
calib00..calib25

0xFE
0xFD
0xFC
0xFB
0xFA
0xF9
0xF8
0xF7
0xF5
0xF4
0xF3
0xF2
0xE1…0xF0
0xE0
0xD0
0x88…0xA1
Registers:
Type:

bit7

bit6

bit5

temp_xlsb<7:4>

press_xlsb<7:4>

t_sb[2:0]
osrs_t[2:0]

bit4

bit3

hum_lsb<7:0>
hum_msb<7:0>
0
temp_lsb<7:0>
temp_msb<7:0>
0
press_lsb<7:0>
press_msb<7:0>
filter[2:0]
osrs_p[2:0]
measuring[0]

bit2

bit1

bit0

0

0

0

0

0

0

spi3w_en[0]mode[1:0]
im_update[0]osrs_h[2:0]calibration data
reset[7:0]
chip_id[7:0]calibration data
Reserved
registers
do notchangeCalibration
data

ControlregistersDataregisters

Statusregisters

Chip ID

Reset

read only

read / write

read only

read only

read only

write only

BST-BME280-DS001-09 | Revision 1.0 | November 2014

Reset
state
0x00
0x80
0x00
0x00
0x80
0x00
0x00
0x80
0x00
0x00
0x00
0x00
individual
0x00
0x60
individual

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5.4 Register description
5.4.1 Register 0xD0 “id”
The “id” register contains the chip identification number chip_id[7:0], which is 0x60. This number
can be read as soon as the device finished the power-on-reset.
5.4.2 Register 0xE0 “reset”
The “reset” register contains the soft reset word reset[7:0]. If the value 0xB6 is written to theregister, the device is reset using the complete power-on-reset procedure. Writing other values
than 0xB6 has no effect. The readout value is always 0x00.
5.4.3 Register 0xF2 “ctrl_hum”
The “ctrl_hum” register sets the humidity data acquisition options of the device. Changes tothis register only become effective after a write operation to “ctrl_meas”.
Table 19: Register 0xF2 “ctrl_hum”
Register 0xF2
“ctrl_hum”

Name

Description

Bit 2, 1, 0

osrs_h[2:0]Controls oversampling of humidity data. See Table 20
for settings and chapter 3.4.1 for details.

Table 20: register settings osrs_h
osrs_h[2:0]

Humidity oversampling000

Skipped (output set to 0x8000)

001

oversampling ×1

010

oversampling ×2

011

oversampling ×4

100

oversampling ×8101, others

oversampling ×16

5.4.4 Register 0xF3 “status”
The “status” register contains two bits which indicate the status of the device.
Table 21: Register 0xF3 “status”
Register 0xF3
“status”

Name

Bit 3

measuring[0]Bit 0

im_update[0]BST-BME280-DS001-09 | Revision 1.0 | November 2014

Description
Automatically set to ‘1’ whenever a conversion is runningand back to ‘0’ when the results have been transferredto the data registers.
Automatically set to ‘1’ when the NVM data are being
copied to image registers and back to ‘0’ when the
copying is done. The data are copied at power-on-resetand before every conversion.

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5.4.5 Register 0xF4 “ctrl_meas”
The “ctrl_meas” register sets the pressure and temperature data acquisition options of thedevice. The register needs to be written after changing “ctrl_hum” for the changes to become
effective.
Table 22: Register 0xF4 “ctrl_meas”
Register 0xF4
“ctrl_meas”

Name

Bit 7, 6, 5

osrs_t[2:0]

Bit 4, 3, 2

osrs_p[2:0]

Bit 1, 0mode[1:0]

Description
Controls oversampling of temperature data. See
Table 24 for settings and chapter 3.4.3 for details.
Controls oversampling of pressure data. See Table 23
for settings and chapter 3.4.2 for details.
Controls the sensor mode of the device. See Table 25
for settings and chapter 3.3 for details.

Table 23: register settings osrs_p
osrs_p[2:0]

Pressure oversampling000

Skipped (output set to 0x80000)

001

oversampling ×1

010

oversampling ×2

011

oversampling ×4

100

oversampling ×8101, others

oversampling ×16

Table 24: register settings osrs_t
osrs_t[2:0]Temperature oversampling000

Skipped (output set to 0x80000)

001

oversampling ×1

010

oversampling ×2

011

oversampling ×4

100

oversampling ×8101, others

oversampling ×16

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Table 25: register settings mode
mode[1:0]

Mode

00

Sleep mode

01 and 10

Forced mode

11

Normal mode

5.4.6 Register 0xF5 “config”
The “config” register sets the rate, filter and interface options of the device. Writes to the “config”
register in normal mode may be ignored. In sleep mode writes are not ignored.
Table 26: Register 0xF5 “config”
Register 0xF5
“config”

Name

Bit 7, 6, 5

t_sb[2:0]

Bit 4, 3, 2

filter[2:0]

Bit 0

spi3w_en[0]Description
Controls inactive duration tstandby in normal mode. See
Table 27 for settings and chapter 0 for details.
Controls the time constant of the IIR filter. See Table 27
for settings and chapter 0 for details.
Enables 3-wire SPI interface when set to ‘1’. See
chapter 6.3 for details.

Table 27: t_sb settings
t_sb[2:0]

tstandby [ms]

000

0.5

001

62.5

010

125

011

250

100

500

101

1000

110

10

111

20

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Table 28: filter settings
filter[2:0]Filter coefficient000

Filter off

001

2

010

4

011

8

100, others

16

5.4.7 Register 0xF7…0xF9 “press” (_msb, _lsb, _xlsb)
The “press” register contains the raw pressure measurement output data up[19:0]. For details
on how to read out the pressure and temperature information from the device, please consult
chapter 4.
Table 29: Register 0xF7 … 0xF9 “press”
Register 0xF7…0xF9“press”

Name

0xF7

press_msb[7:0]0xF8

press_lsb[7:0]

0xF9 (bit 7, 6, 5, 4)

press_xlsb[3:0]Description
Contains the MSB part up[19:12] of the raw pressure
measurement output data.
Contains the LSB part up[11:4] of the raw pressure
measurement output data.
Contains the XLSB part up[3:0] of the raw pressure
measurement output data. Contents depend on
temperature resolution.

5.4.8 Register 0xFA…0xFC “temp” (_msb, _lsb, _xlsb)
The “temp” register contains the raw temperature measurement output data ut[19:0]. For details
on how to read out the pressure and temperature information from the device, please consult
chapter 4.
Table 30: Register 0xFA … 0xFC “temp”
Register 0xFA…0xFC“temp”

Name

0xFA

temp_msb[7:0]0xFB

temp_lsb[7:0]0xFC (bit 7, 6, 5, 4)

temp_xlsb[3:0]

BST-BME280-DS001-09 | Revision 1.0 | November 2014

Description
Contains the MSB part ut[19:12] of the raw temperature
measurement output data.
Contains the LSB part ut[11:4] of the raw temperature
measurement output data.
Contains the XLSB part ut[3:0] of the raw temperature
measurement output data. Contents depend on pressure
resolution.

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5.4.9 Register 0xFD…0xFE “hum” (_msb, _lsb)
The “temp” register contains the raw temperature measurement output data ut[19:0]. For details
on how to read out the pressure and temperature information from the device, please consult
chapter 4.
Table 31: Register 0xFD … 0xFE “hum”
Register 0xFD…0xFE
“hum”

Name

0xFD

hum_msb[7:0]0xFE

temp_lsb[7:0]

BST-BME280-DS001-09 | Revision 1.0 | November 2014

Description
Contains the MSB part uh[15:8] of the raw humidity
measurement output data.
Contains the LSB part uh[7:0] of the raw humidity
measurement output data.

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6. Digital interfaces
The BME280 supports the I²C and SPI digital interfaces; it acts as a slave for both protocols.
The I²C interface supports the Standard, Fast and High Speed modes. The SPI interface
supports both SPI mode ‘00’ (CPOL = CPHA = ‘0’) and mode ‘11’ (CPOL = CPHA = ‘1’) in 4wire and 3-wire configuration.
The following transactions are supported: Single byte write
 multiple byte write (using pairs of register addresses and register data) single byte read multiple byte read (using a single register address which is auto-incremented)

6.1 Interface selection
Interface selection is done automatically based on CSB (chip select) status. If CSB is connected
to VDDIO, the I²C interface is active. If CSB is pulled down, the SPI interface is activated. After
CSB has been pulled down once (regardless of whether any clock cycle occurred), the I²C
interface is disabled until the next power-on-reset. This is done in order to avoid inadvertently
decoding SPI traffic to another slave as I²C data. Since the device startup is deferred until both
VDD and VDDIO are established, there is no risk of incorrect protocol detection because of thepower-up sequence used. However, if I²C is to be used and CSB is not directly connected to
VDDIO but is instead connected to a programmable pin, it must be ensured that this pin alreadyoutputs the VDDIO level during power-on-reset of the device. If this is not the case, the device will
be locked in SPI mode and not respond to I²C commands.

6.2 I²C Interface
The I²C slave interface is compatible with Philips I²C Specification version 2.1. For detailed
timings, please review Table 33. All modes (standard, fast, high speed) are supported. SDA andSCL are not pure open-drain. Both pads contain ESD protection diodes to VDDIO and GND. As
the devices does not perform clock stretching, the SCL structure is a high-Z input without drain
capability.

Figure 8: SDI/SCK ESD drawing

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The 7-bit device address is 111011x. The 6 MSB bits are fixed. The last bit is changeable by
SDO value and can be changed during operation. Connecting SDO to GND results in slave
address 1110110 (0x76); connection it to VDDIO results in slave address 1110111 (0x77), whichis the same as BMP280’s I²C address. The SDO pin cannot be left floating; if left floating, theI²C address will be undefined.
The I²C interface uses the following pins:
 SCK: serial clock (SCL) SDI: data (SDA) SDO: Slave address LSB (GND = ‘0’, VDDIO = ‘1’)
CSB must be connected to VDDIO to select I²C interface. SDI is bi-directional with open drain to
GND: it must be externally connected to VDDIO via a pull up resistor. Refer to chapter 7 forconnection instructions.
The following abbreviations will be used in the I²C protocol figures:
 S
Start
 P
Stop
 ACKS
Acknowledge by slave
 ACKM
Acknowledge by master NACKM
Not acknowledge by master6.2.1 I²C write
Writing is done by sending the slave address in write mode (RW = ‘0’), resulting in slave
address 111011X0 (‘X’ is determined by state of SDO pin. Then the master sends pairs ofregister addresses and register data. The transaction is ended by a stop condition. This is
depicted in Figure 9.
Control byte
Slave Address

Start

S

1

1

1

0

1

Register address (A0h)

RW ACKS

1

X

0

Data byte

1

0

1

0

0

0

0

Register data - address A0h

ACKS

0

bit7

bit6

bit5

Control byte

1

0

1

0

0

bit3

bit2 bit1 bit0…

Data byte

Register address (A1h)

…

bit4

ACKS

0

0

Register data - address A1h

ACKS

1

bit7

bit6

bit5

bit4

bit3

bit2 bit1 bit0

ACKS StopP

Figure 9: I²C multiple byte write (not auto-incremented)

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6.2.2 I²C read
To be able to read registers, first the register address must be sent in write mode (slave address
111011X0). Then either a stop or a repeated start condition must be generated. After this theslave is addressed in read mode (RW = ‘1’) at address 111011X1, after which the slave sends
out data from auto-incremented register addresses until a NOACKM and stop condition occurs.
This is depicted in Figure 10, where register 0xF6 and 0xF7 are read.
Control byte
Slave Address

Start

S

1

1

1

0

1

Register address (F6h)

RW ACKS

1

X

0

1

1

1

1

0

1

ACKS

1

0

Data byte
Slave Address

Start

S

1

1

1

0

1

Register data - address F6h

RW ACKS

1

X

1

Data byte

bit7

bit6

bit5

bit4

bit3

bit2

Register data - address F7h

ACKM

bit1 bit0

bit7

bit6 bit5 bit4 bit3 bit2 bit1 bit0

NOACKM StopP

Figure 10: I²C multiple byte read

6.3 SPI interface
The SPI interface is compatible with SPI mode ‘00’ (CPOL = CPHA = ‘0’) and mode ‘11’ (CPOL= CPHA = ‘1’). The automatic selection between mode ‘00’ and ‘11’ is determined by the valueof SCK after the CSB falling edge.
The SPI interface has two modes: 4-wire and 3-wire. The protocol is the same for both. The 3wire mode is selected by setting ‘1’ to the register spi3w_en. The pad SDI is used as a data padin 3-wire mode.
The SPI interface uses the following pins:
 CSB: chip select, active low SCK: serial clock SDI: serial data input; data input/output in 3-wire mode SDO: serial data output; hi-Z in 3-wire mode
Refer to chapter 7 for connection instructions.
CSB is active low and has an integrated pull-up resistor. Data on SDI is latched by the device at
SCK rising edge and SDO is changed at SCK falling edge. Communication starts when CSB
goes to low and stops when CSB goes to high; during these transitions on CSB, SCK must be
stable. The SPI protocol is shown in Figure 11. For timing details, please review Table 34.

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CSB

SCK

SDI
RW

AD6

AD5

AD4

AD3

AD2

AD1

AD0

DI7

DI6

DI5

DI4

DI3

DI2

DI1

DO7

DO6 DO5

DO4

DO3

DO2 DO1

DI0

SDO
DO0 tri-state

Figure 11: SPI protocol (shown for mode ‘11’ in 4-wire configuration)
In SPI mode, only 7 bits of the register addresses are used; the MSB of register address is not
used and replaced by a read/write bit (RW = ‘0’ for write and RW = ‘1’ for read).
Example: address 0xF7 is accessed by using SPI register address 0x77. For write access, thebyte 0x77 is transferred, for read access, the byte 0xF7 is transferred.
6.3.1 SPI write
Writing is done by lowering CSB and sending pairs control bytes and register data. The control
bytes consist of the SPI register address (= full register address without bit 7) and the write
command (bit7 = RW = ‘0’). Several pairs can be written without raising CSB. The transaction isended by a raising CSB. The SPI write protocol is depicted in Figure 12.
Control byte
Start

RW

CSB
=
0

0

Data byte

Register address (F4h)

1

1

1

0

1

Control byte

Data register - address F4h

0

0

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

0

Data byte

Register address (F5h)

RW
1

1

1

0

1

0

Data register - adress F5h

1

bit7

bit6

bit5

bit4

bit3

bit2

Stop
bit1

bit0

CSB
=
1

Figure 12: SPI multiple byte write (not auto-incremented)
6.3.2 SPI read
Reading is done by lowering CSB and first sending one control byte. The control bytes consistof the SPI register address (= full register address without bit 7) and the read command (bit 7 =RW = ‘1’). After writing the control byte, data is sent out of the SDO pin (SDI in 3-wire mode);
the register address is automatically incremented. The SPI read protocol is depicted in Figure
13.
Control byte
Register address (F6h)

Start RW
CSB
=
0

1

1

1

1

0

1

1

0

Data byte

Data byte

Data register - address F6h

Data register - address F7h

bit15 bit14 bit13 bit12 bit11 bit10

bit9

bit8

bit7

bit6

bit5

bit4

bit3

bit2

Stop
bit1

bit0

CSB
=
1

Figure 13: SPI multiple byte read

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6.4 Interface parameter specification
6.4.1 General interface parameters
The general interface parameters are given in Table 32 below.
Table 32: interface parameters
Parameter

SymbolCondition

Input low level
Input high level2
Output low level I C
2
Output low level I C
Output low level SPI
Output low level SPI

Vil_siVih_si
Vol_SDI
Vol_SDI_1.2
Vol_SDO
Vol_SDO_1.2

VDDIO=1.2 V to 3. 6V
VDDIO=1.2 V to 3.6 V
VDDIO=1.62 V, Iol=3 mA
VDDIO=1.20 V, Iol=3 mA
VDDIO=1.62 V, Iol=1 mA
VDDIO=1.20 V, Iol=1 mA
VDDIO=1.62 V, Ioh=1 mA(SDO, SDI)VDDIO=1.20 V, Ioh=1 mA(SDO, SDI)Internal CSB pull-up
resistance to VDDIO

Output high level

Voh

Output high level

Voh_1.2

Pull-up resistor

Rpull

2

Cb

I C bus load capacitor

Min

Typ

Max

Unit

20

%VDDIO%VDDIO%VDDIO%VDDIO%VDDIO%VDDIO

80
20
23
20
23
80

%VDDIO60%VDDIO

70

120

On SDI and SCK

190

kΩ

400

pF

6.4.2 I²C timings
For I²C timings, the following abbreviations are used:
 “S&F mode” = standard and fast mode “HS mode” = high speed mode Cb = bus capacitance on SDA line
All other naming refers to I²C specification 2.1 (January 2000).
The I²C timing diagram is in Figure 14. The corresponding values are given in Table 33.

SDI
tBUF
tf

tLOW
SCK

tHIGH
tHDSTAtrtHDDATtSUDAT

SDItSUSTAtSUSTO

Figure 14: I²C timing diagram

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Table 33: I²C timings
Parameter

Symbol

SDI setup time

tSU;DATSDI hold time

tHD;DATSCK low pulsetLOW

SCK low pulse

tLOW

ConditionMin

S&F Mode
HS modeS&F Mode, Cb≤100 pF
S&F Mode, Cb≤400 pF
HS mode, Cb≤100 pF
HS mode, Cb≤400 pF
HS mode, Cb≤100 pF
VDDIO = 1.62 V
HS mode, Cb≤100 pF
VDDIO = 1.2 V

160
30
80
90
18
24

Typ

Max

Unit

115
150

ns
ns
ns
ns
ns
ns

160

ns

210

ns

The above-mentioned I2C specific timings correspond to the following internal added delays: Input delay between SDI and SCK inputs: SDI is more delayed than SCK by typically
100 ns in Standard and Fast Modes and by typically 20 ns in High Speed Mode.
 Output delay from SCK falling edge to SDI output propagation is typically 140 ns inStandard and Fast Modes and typically 70 ns in High Speed Mode.
6.4.3 SPI timings
The SPI timing diagram is in Figure 15, while the corresponding values are given in Table 34.
All timings apply both to 4- and 3-wire SPI.
T_hold_csb

T_setup_csb

CSB

T_low_sck

T_high_sck

SCK

SDI

T_setup_sdi

T_hold_sdi

SDO

T_delay_sdo

Figure 15: SPI timing diagram

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Table 34: SPI timings
Parameter

SymbolSPI clock input frequency
SCK low pulse
SCK high pulse
SDI setup time
SDI hold time
SDO output delay
SDO output delay
CSB setup time
CSB hold time

F_spi
T_low_sck
T_high_sck
T_setup_sdi
T_hold_sdi
T_delay_sdo
T_delay_sdo
T_setup_csb
T_hold_csb

BST-BME280-DS001-09 | Revision 1.0 | November 2014

Condition

Min
0
20
20
20
20

25 pF load, VDDIO=1.6 V min
25 pF load, VDDIO=1.2 V min

Typ

Max

Unit

10

MHz
ns
ns
ns
ns
ns
ns
ns
ns

30
40
20
20

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7. Pin-out and connection diagram
7.1 Pin-out

8
VDD

1
GND

1
GND

8
VDD
Pin 1
marker

7
GND

2
CSB

2
CSB

7
GND

TOP VIEW(pads not visible)
6
VDDIO

BOTTOM VIEW
(pads visible)
3
SDI

3
SDI

6
VDDIO

4
SCK

4
SCK

5
SDO

Vent hole
5
SDO

Figure 16: Pin-out top and bottom view
Note: The pin numbering of BME280 is performed in the untypical clockwise direction when
seen in top view and counter-clockwise when seen in bottom view.
Table 35: Pin description
SPI 4W

Connect to
SPI 3W
GND

I²C

Chip select

CSB

CSB

VDDIO

In/OutSerial data input

SDI

SDI/SDO

SDA

SCK

In

Serial clock input

SCK

SCK

SCL

5

SDO

In/OutSerial data output

SDO

DNC

GND fordefault
address

6

VDDIO

Supply7

GND

SupplyDigital / Interface
supplyGround8

VDD

SupplyAnalog supply

Pin

Name

I/O Type

Description

1

GND

SupplyGround

2

CSB

In

3

SDI

4

BST-BME280-DS001-09 | Revision 1.0 | November 2014

VDDIO
GND
VDD

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7.2 Connection diagram I2C
VDD

VDDIO

8
VDD

1
GND

7
GND

2
CSB
TOP VIEW(pads not visible)

6
VDDIO

R1

R2

3
SDI

SDA

4
SCK

SCL

Vent hole
5
SDO

I2C address bit 0
GND: '0'; VDDIO: '1'
C1

C2

Figure 17: I²C connection diagram
Notes:
 The recommended value for C1, C2 is 100 nF
 The value for the pull-up resistors R1, R2 should be based on the interface timing and thebus load; a normal value is 4.7 kΩ A direct connection between CSB and VDDIO is required

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7.3 Connection diagram 4-wire SPI
VDD

VDDIO

8
VDD

1
GND

7
GND

2
CSB

CSB

3
SDI

SDI

4
SCK

SCK

TOP VIEW(pads not visible)
6
VDDIO
Vent hole
5
SDO

SDO

C1

C2

Figure 18: 4-wire SPI connection diagram
Note: The recommended value for C1, C2 is 100 nF

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7.4 Connection diagram 3-wire SPI
VDD

VDDIO

8
VDD

1
GND

7
GND

2
CSB

CSB

3
SDI

SDI/SDO

4
SCK

SCK

TOP VIEW(pads not visible)
6
VDDIO
Vent hole
5
SDO
C1

C2

Figure 19: 3-wire SPI connection diagram
Note: The recommended value for C1, C2 is 100 nF

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7.5 Package dimensions

Figure 20: Package dimensions for top, bottom and side view

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7.6 Landing pattern recommendation
For the design of the landing pattern, the following dimensioning is recommended:

Figure 21: Recommended landing pattern (top view)
Note: red areas demark exposed PCB metal pads.
 In case of a solder mask defined (SMD) PCB process, the land dimensions should be
defined by solder mask openings. The underlying metal pads are larger than these
openings.
 In case of a non solder mask defined (NSMD) PCB process, the land dimensions should
be defined in the metal layer. The mask openings are larger than these metal pads.

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7.7 Marking
7.7.1 Mass production devices
Table 36: Marking of mass production parts
Marking5

6

7

Description

CCC

Lot counter: 3 alphanumeric digits,
variable to generate mass production
trace-codeT

Product number: 1 alphanumeric digit,
fixed to identify product type, T = “U”“U” is associated with the product
BME280 (part number 0 273 141 185)

L

Sub-contractor ID: 1 alphanumeric digit,
variable to identify sub-contractor (L = “P”)

8

CCC
TL

Vent
hole

SymbolPin 1marker4

3

2

1

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7.7.2 Engineering samples
Table 37: Marking of engineering samples
Marking

5

6

7

SymbolXX

Sample ID: 2 alphanumeric digits,
variable to generate trace-code

NEng. Sample ID: 1 alphanumeric digit,
fixed to identify engineering sample,
N = “ * ” or “e” or “E”

CC

Counter ID: 2 alphanumeric digits,
variable to generate trace-code

8

XXN
CC

Vent
hole

Description

Pin 1
marker4

3

2

1

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7.8 Soldering guidelines and reconditioning recommendations
The moisture sensitivity level of the BME280 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. The minimum height of thesolder after reflow shall be at least 50µm. This is required for good mechanical decoupling
between the sensor device and the printed circuit board (PCB).

Figure 22: Soldering profile

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7.9 Reconditioning Procedure
After exposing the device to operating conditions, which exceed the limits specified in
section 1.2, e.g. after reflow, the humidity sensor may possess an additional offset. Therefore
the following reconditioning procedure is mandatory to restore the calibration state:
1. Dry-Baking:
2. Re-Hydration:

120 °C at <5% rH for 2 h
70 °C at 75% rH for 6 h

or alternatively
1. Dry-Baking:
2. Re-Hydration:

120 °C at <5% rH for 2 h
25 °C at 75% rH for 24 hor alternatively after solder reflow only
1. Do not perform Dry-Baking
2. Ambient Re-Hydration:~25 °C at >40% rH for >5d

7.10 Tape and reel specification
7.10.1 Dimensions

Figure 23: Tape and Reel dimensions
Quantity per reel: 10 kpcs.

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7.10.2 Orientation within the reelFigure 24: Orientation within tape

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7.11 Mounting and assembly recommendations
In order to achieve the specified performance for you design, the following recommendations
and the “Handling, soldering & mounting instructions BME280” should be taken into
consideration when mounting a pressure sensor on a printed-circuit board (PCB): The clearance above the metal lid shall be 0.1mm at minimum.
 For the device housing appropriate venting needs to be provided in case the ambientpressure shall be measured.
 Liquids shall not come into direct contact with the device.
 During operation the sensor chip is sensitive to light, which can influence the accuracy ofthe measurement (photo-current of silicon). The position of the vent hole minimizes thelight exposure of the sensor chip. Nevertheless, Bosch Sensortec recommends avoiding
the exposure of BME280 to strong light sources.
 Soldering may not be done using vapor phase processes since the sensor will bedamaged by the liquids used in these processes.

7.12 Environmental safety
7.12.1 RoHS
The BME280 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 andelectronic equipment.
7.12.2 Halogen content
The BME280 is halogen-free. For more details on the analysis results please contact yourBosch Sensortec representative.
7.12.3 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 packageof the BME280.
While Bosch Sensortec took care that all of the technical packages parameters are describedabove are 100% identical for all sources, there can be differences in the chemical content andthe internal structural between the different package sources.
However, as secured by the extensive product qualification process of Bosch Sensortec, thishas no impact to the usage or to the quality of the BME280 product.

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8. Appendix A: Alternative compensation formulas
8.1 Compensation formulas in double precision floating point
Please note that it is strongly advised to use the API available from Bosch Sensortec to perform
readout and compensation. If this is not wanted, the code below can be applied at the user’srisk. Both pressure and temperature values are expected to be received in 20 bit format,
positive, stored in a 32 bit signed integer. Humidity is expected to be received in 16 bit format,
positive, stored in a 32 bit signed integer.
The variable t_fine (signed 32 bit) carries a fine resolution temperature value over to thepressure compensation formula and could be implemented as a global variable.
The data type “BME280_S32_t” should define a 32 bit signed integer variable type and could
usually be defined as “long signed int”. The revision of the code is rev. 1.1 (pressure andtemperature) and rev. 1.0 (humidity).
Compensating the measurement value with double precision gives the best possible accuracy
but is only recommended for PC applications.
// Returns temperature in DegC, double precision. Output value of “51.23” equals 51.23 DegC.
// t_fine carries fine temperature as global value
BME280_S32_t t_fine;double BME280_compensate_T_double(BME280_S32_t adc_T){
double var1, var2, T;
var1 = (((double)adc_T)/16384.0 – ((double)dig_T1)/1024.0) * ((double)dig_T2);
var2 = ((((double)adc_T)/131072.0 – ((double)dig_T1)/8192.0) *(((double)adc_T)/131072.0 – ((double) dig_T1)/8192.0)) * ((double)dig_T3);
t_fine = (BME280_S32_t)(var1 + var2);
T = (var1 + var2) / 5120.0;
return T;}// Returns pressure in Pa as double. Output value of “96386.2” equals 96386.2 Pa = 963.862 hPa
double BME280_compensate_P_double(BME280_S32_t adc_P){
double var1, var2, p;
var1 = ((double)t_fine/2.0) – 64000.0;
var2 = var1 * var1 * ((double)dig_P6) / 32768.0;
var2 = var2 + var1 * ((double)dig_P5) * 2.0;
var2 = (var2/4.0)+(((double)dig_P4) * 65536.0);
var1 = (((double)dig_P3) * var1 * var1 / 524288.0 + ((double)dig_P2) * var1) / 524288.0;
var1 = (1.0 + var1 / 32768.0)*((double)dig_P1);
if (var1 == 0.0){
return 0; // avoid exception caused by division by zero}p = 1048576.0 – (double)adc_P;
p = (p – (var2 / 4096.0)) * 6250.0 / var1;
var1 = ((double)dig_P9) * p * p / 2147483648.0;
var2 = p * ((double)dig_P8) / 32768.0;
p = p + (var1 + var2 + ((double)dig_P7)) / 16.0;
return p;}// Returns humidity in %rH as as double. Output value of “46.332” represents 46.332 %rH
double bme280_compensate_H_double(BME280_S32_t adc_H);{
double var_H;
var_H = (((double)t_fine) – 76800.0);
var_H = (adc_H – (((double)dig_H4) * 64.0 + ((double)dig_H5) / 16384.0 * var_H)) *(((double)dig_H2) / 65536.0 * (1.0 + ((double)dig_H6) / 67108864.0 * var_H *(1.0 + ((double)dig_H3) / 67108864.0 * var_H)));
var_H = var_H * (1.0 – ((double)dig_H1) * var_H / 524288.0);
if (var_H > 100.0)
var_H = 100.0;
else if (var_H < 0.0)
var_H = 0.0;
return var_H;}

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8.2 Pressure compensation in 32 bit fixed point
Please note that it is strongly advised to use the API available from Bosch Sensortec to perform
readout and compensation. If this is not wanted, the code below can be applied at the user’srisk. Both pressure and temperature values are expected to be received in 20 bit format,
positive, stored in a 32 bit signed integer.
The variable t_fine (signed 32 bit) carries a fine resolution temperature value over to thepressure compensation formula and could be implemented as a global variable.
The data type “BME280_S32_t” should define a 32 bit signed integer variable type and canusually be defined as “long signed int”.
The data type “BME280_U32_t” should define a 32 bit unsigned integer variable type and canusually be defined as “long unsigned int”.
Compensating the pressure value with 32 bit integer has an accuracy of typically 1 Pa (1sigma). At high filter levels this adds a significant amount of noise to the output values andreduces their resolution.
// Returns temperature in DegC, resolution is 0.01 DegC. Output value of “5123” equals 51.23 DegC.
// t_fine carries fine temperature as global value
BME280_S32_t t_fine;
BME280_S32_t BME280_compensate_T_int32(BME280_S32_t adc_T){
BME280_S32_t var1, var2, T;
var1 = ((((adc_T>>3) – ((BME280_S32_t)dig_T1<<1))) * ((BME280_S32_t)dig_T2)) >> 11;
var2 = (((((adc_T>>4) – ((BME280_S32_t)dig_T1)) * ((adc_T>>4) – ((BME280_S32_t)dig_T1))) >> 12) *((BME280_S32_t)dig_T3)) >> 14;
t_fine = var1 + var2;
T = (t_fine * 5 + 128) >> 8;
return T;}// Returns pressure in Pa as unsigned 32 bit integer. Output value of “96386” equals 96386 Pa = 963.86 hPa
BME280_U32_t BME280_compensate_P_int32(BME280_S32_t adc_P){
BME280_S32_t var1, var2;
BME280_U32_t p;
var1 = (((BME280_S32_t)t_fine)>>1) – (BME280_S32_t)64000;
var2 = (((var1>>2) * (var1>>2)) >> 11 ) * ((BME280_S32_t)dig_P6);
var2 = var2 + ((var1*((BME280_S32_t)dig_P5))<<1);
var2 = (var2>>2)+(((BME280_S32_t)dig_P4)<<16);
var1 = (((dig_P3 * (((var1>>2) * (var1>>2)) >> 13 )) >> 3) + ((((BME280_S32_t)dig_P2) * var1)>>1))>>18;
var1 =((((32768+var1))*((BME280_S32_t)dig_P1))>>15);
if (var1 == 0){
return 0; // avoid exception caused by division by zero}p = (((BME280_U32_t)(((BME280_S32_t)1048576)-adc_P)-(var2>>12)))*3125;
if (p < 0x80000000){
p = (p << 1) / ((BME280_U32_t)var1);}else{
p = (p / (BME280_U32_t)var1) * 2;}
var1 = (((BME280_S32_t)dig_P9) * ((BME280_S32_t)(((p>>3) * (p>>3))>>13)))>>12;
var2 = (((BME280_S32_t)(p>>2)) * ((BME280_S32_t)dig_P8))>>13;
p = (BME280_U32_t)((BME280_S32_t)p + ((var1 + var2 + dig_P7) >> 4));return p;}

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9. Appendix B: Measurement time and current calculation
In this chapter, formulas are given to calculate measurement rate, filter bandwidth and current
consumption in different settings.

9.1 Measurement time
The active measurement time depends on the selected values for humidity, temperature andpressure oversampling and can be calculated in milliseconds using the formulas below.

For example, using temperature oversampling ×1, pressure oversampling ×4 and no humidity
measurement, the measurement time is:

9.2 Measurement rate in forced mode
In forced mode, the measurement rate depends on the rate at which it is forced by the master.
The highest possible frequency in Hz can be calculated as:

If measurements are forced faster than they can be executed, the data rate saturates at theattainable data rate. For the example above with 11.5 ms measurement time, the typicallyachievable output data rate would be:

9.3 Measurement rate in normal mode
The measurement rate in normal mode depends on the measurement time and the standby
time and can be calculated in Hz using the following formula:

The accuracy of tstandby is described in the specification parameter Δtstandby. For the example
above with 11.5 ms measurement time, setting normal mode with a standby time of 62.5 ms
would result in a data rate of:

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9.4 Response time using IIR filter
When using the IIR filter, the response time of the sensor depends on the selected filter
coefficient and the data rate used. It can be calculated using the following formula:

For the example above with a data rate of 13.51 Hz, the user could select a filter coefficient of 8.
According to Table 6, the number of samples needed to reach 75% of a step response using
this filter setting is 11. The response time with filter is therefore:

9.5 Current consumption
The current consumption depends on the selected oversampling settings, the measurement
rate and the sensor mode, but not on the IIR filter setting. It can be calculated as:

Note that the only difference between forced and normal mode current consumption is that thecurrent for the inactive time is either IDDSL or IDDSB. For the example above, the current would be

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10. Legal disclaimer
10.1 Engineering samples
Engineering Samples are marked with an asterisk (*) or (e) or (E). Samples may vary from thevalid 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 ofengineering 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 andall warranties and liabilities of any kind, including without limitation warranties of noninfringement of intellectual property rights or copyrights of any third party. The information givenin 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 ofintellectual property rights or copyrights or regarding functionality, performance or error has
been made.

10.4 Handling Instructions
Detailed handling instructions are described in the document “handling, soldering & mounting
instructions (HSMI)”.
Important to highlight is the directive to avoid during manufacturing, transport and usage of thesensor in devices the contact of high concentration of chemical solvents and long exposure
times. Chemical interactions of chemical compounds with the sensor shall be prevented. Theseare especially outgassing of corrugated plastic, organic glues, sticky tape made with adhesives,labels, marker or outgassing package materials such as bubble wrap, foams and others shall be
avoided. It is recommended to ventilate the production and manufacturing area.

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11. Document history and modificationRev. No0.1
1.0

Chapter

Description of modification/changes
Document creationDate
2012-11-06

Final datasheet

2014-11-12

Bosch Sensortec GmbHGerhard-Kindler-Strasse 872770 Reutlingen / Germany
contact@bosch-sensortec.com
www.bosch-sensortec.com
Modifications reserved
Specifications subject to change without notice
Document number: BST-BME280-DS001-09
Revision_1.0_November 2014

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