BME280 — temperature, humidity and pressure¶
Being prepared
Chosen for the catalogue; the driver has not shipped yet. The figures below still need checking against the datasheet.
What it does¶
Three measurements from one part the size of a grain of rice: air temperature, relative humidity and barometric pressure. It is the usual first sensor on any board that has to know something about the room it is in — a cabinet, a greenhouse, a boiler room.
The pressure reading is good enough to see weather changing and to work out altitude to within a metre or so, which is more often useful than it sounds.
Parameters¶
| Measures | Temperature, relative humidity, barometric pressure |
| Temperature range | −40 … 85 °C |
| Humidity range | 0 … 100 %RH |
| Pressure range | 300 … 1100 hPa |
| Interface | I²C or SPI |
Bus and addressing¶
I²C, address 0x76 or 0x77, chosen by how the SDO pin is tied. The same part also speaks SPI, which is worth knowing when the I²C bus is already busy.
BMP280 is not BME280
They look identical and cost nearly the same. The BMP280 has no humidity sensor. Check the marking, not the listing.
Wiring¶
In a project¶
To be written.
Traps¶
| Trap | What to do |
|---|---|
| Self-heating | The part warms itself, and reads high by a degree or so if it is polled hard or sits next to something warm. Poll slowly, and keep it away from the supply. |
| Measuring the box, not the room | In a sealed enclosure it reports the enclosure. If the number is meant to be the room, the sensor belongs outside the box. |