Data Sheet

Bosch Sensortec | BME280 Data sheet
17 | 55
Modifications reserved | Data subject to change without notice
Document number: BST-BME280-DS002-15
Revision_1.6_092018
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 and temperature 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 not needed and has not been implemented.
The flow is depicted in the diagram below.
Measure temperature
(oversampling set by osrs_t;
skip if osrs_t = 0)
Start
measurement cycle
Measure pressure
(oversampling set by osrs_p;
skip if osrs_p = 0)
IIR filter enabled?
End
measurement cycle
IIR filter initialised?
Copy ADC values
to filter memory
(initalises IIR filter)
No
Update filter memory using
filter memory, ADC value
and filter coefficient
No
Yes
Yes
Copy filter memory
to output registers
Measure humidity
(oversampling set by osrs_h;
skip if osrs_h = 0)
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 is detailed in chapter
5.4.3. For the humidity measurement, oversampling is possible to reduce the noise. 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 is detailed 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 3.4.4) and the oversampling 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 in chapter 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 3.4.4) and the
oversampling setting (see chapter 5.4.5):
 When the IIR filter is enabled, the temperature resolution is 20 bit.