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Bosch Sensortec · Integrated circuit

BME280 Humidity, Pressure and Temperature Sensor

Three environmental measurements in a grain of rice, over I2C or SPI. Accurate enough on pressure to tell which floor of a building you are on.

Cheat sheet (SVG)
Logic level
1.71-3.6 V
Package
LGA-8, 2.5 x 2.5 mm

1.Pinout diagram

Highlight a signalhover to preview, click to keep

Pins 1-4

BME280

Pins 5-8

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Logic level
1.71-3.6 V
Package
LGA-8, 2.5 x 2.5 mm

Fig. 1. BME280 Humidity, Pressure and Temperature Sensor, LGA-8, 2.5 x 2.5 mm. Hover or tap a signal to light up every pin that carries it.

2.Watch out

  • The BMP280 is the same part without humidity, in the same package with the same pinout and nearly the same register map. They are routinely sold as each other. Read the chip ID register: 0x60 is a BME280, 0x58 is a BMP280.
  • VDD and VDDIO are separate supplies on purpose. VDDIO sets the logic level, so the sensor can run its analog side at 1.8 V and still talk to a 3.3 V bus. Modules usually tie them together behind a regulator.
  • It is not 5 V tolerant on any pin. A bare chip wired to an Uno is a dead chip; the breakout boards that survive it have a regulator and a level shifter doing the work.
  • CSB picks the interface, and it is sampled rather than strapped: tie it to VDDIO for I2C, or drive it as chip select for SPI. Left floating it will not reliably be either.
  • SDO is the address bit in I2C mode. Low gives 0x76 and high gives 0x77, and it must be driven, not left open. Two sensors on one bus is the most this part will do.
  • The temperature reading is the die's own, and the die sits next to a thing you are powering. Forced mode, one reading at a time with the chip asleep in between, reports ambient. Continuous mode at a high rate reports the chip warming itself up, usually by a degree or two.
  • Pressure comes out in Pa with a 20-bit resolution, and the compensation routine in the datasheet is not optional: the raw value is meaningless without the per-chip calibration coefficients read out of registers 0x88 onward.
  • The pin table here is the chip's own, as numbered by Bosch. The real package is a square LGA with pads on all four sides, so these are the datasheet's numbers rather than a shape you can read off the part.

3.Minimum circuit on I2C

What has to go around the chip before it will run.

VCCGNDBME280100 nF ceramic between VDD (8) and GND100 nFceramic100 nF ceramic between VDDIO (6) and GND100 nFceramicInterface link between CSB (2) and VCCInterfacelinkAddress link between SDO (5) and GNDAddresslink4.7 kOhm between SDI (3) and VCC4.7 kOhm4.7 kOhm between SCK (4) and VCC4.7 kOhmGND (1) to GNDVDDIO (6) to VCCGND (7) to GNDVDD (8) to VCCGND 1CSB 2SDI 3SCK 4SDO 5VDDIO 6VDDIO 6GND 7VDD 8VDD 8
Fig. 2. Minimum circuit on I2C, drawn from Table 1. Crossing wires are not connected.
Table 1. External parts, and why each one is there.
PartBetween
100 nF ceramicVDD (8) to GND
100 nF ceramicVDDIO (6) to GND
Interface linkCSB (2) to VCC
Address linkSDO (5) to GND
4.7 kOhmSDI (3) to VCC
4.7 kOhmSCK (4) to VCC

Both ground pins must be connected. For SPI, leave the pull-ups off and treat SDI as MOSI, SDO as MISO, SCK as clock and CSB as chip select.

4.Full pin reference

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for BME280 Humidity, Pressure and Temperature Sensor
PinNameFunctions

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Primary sources

Found a wrong pin? The whole board is one file, data/boards/bme280.json.

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