Module bme280 

Bosch BME280 temperature, pressure, and humidity sensor.

The BME280 ships raw, uncompensated readings plus a block of per-chip calibration coefficients; the real measurement only appears after running those raw values through Bosch’s compensation formulas. Those formulas are the classic place a from-memory port goes subtly wrong, so the integer arithmetic here is ported from Bosch’s published reference code, and the tests cross-check it against the reference floating-point form and the datasheet’s worked temperature example.

A caller reads the calibration registers once with Calibration::from_registers, then reads the data registers each cycle into a RawMeasurement and calls Calibration::compensate. The control registers (CtrlHum, CtrlMeas, Config) and the measurement-time formula are here too, and the Bme280 driver (the embedded-hal feature) runs the whole sequence over an I2C or SPI bus.

Modules

register

The BME280 register addresses used to read calibration and measurements.

sim

A BME280 that is not there.

Structs

Bme280

A BME280 on an I2C or SPI bus, measuring on demand in forced mode.

Calibration

The per-chip calibration coefficients read from the sensor’s calibration registers.

Config

The configuration register (0xF5, config).

CtrlHum

The humidity control register (0xF2, ctrl_hum).

CtrlMeas

The measurement control register (0xF4, ctrl_meas).

Measurement

A compensated BME280 measurement.

RawMeasurement

The raw, uncompensated readings from the BME280 data registers.

Enums

Filter

The IIR filter coefficient, the filter[2:0] field.

Mode

The power mode selected by the mode[1:0] field.

Oversampling

An oversampling setting for one of the three measurements.

Standby

The inactive period between measurements in normal mode, the t_sb[2:0] field.

Constants

CALIB_HUMIDITY_LEN

The number of bytes in the humidity calibration block.

CALIB_TEMP_PRESS_LEN

The number of bytes in the temperature and pressure calibration block.

CHIP_ID

The value the chip-id register (0xD0) returns for a BME280.

DATA_LEN

The number of bytes in the burst-read data block.

I2C_ADDRESS_PRIMARY

The I2C address with the SDO pin tied low.

I2C_ADDRESS_SECONDARY

The I2C address with the SDO pin tied high.

RESET_WORD

The soft-reset word: writing it to register::RESET runs the power-on sequence.

SKIPPED_HUMIDITY

The value a skipped humidity measurement leaves in its registers.

SKIPPED_OUTPUT

The value a skipped temperature or pressure measurement leaves in its registers.

STARTUP_MICROS

The start-up time from power-on or reset until the part accepts a transfer, in microseconds.

STATUS_POLLS

How many times the status register is polled, 1 ms apart, before a conversion or a reset is called overdue.

Functions

image_updating

Reads the im_update flag of a status register value.

max_measurement_micros

The longest one measurement cycle can take, in microseconds.

measuring

Reads the measuring flag of a status register value.

typical_measurement_micros

The typical time one measurement cycle takes, in microseconds.