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BME280 sensor driver

This is an I2C driver for the Bosch BME280 temperature / humidity / pressure sensor. The SPI mode of this chip is not supported.

API

The default initialization using bme-init puts the chip into continuous conversion mode, which means that it can be read anytime using bme-data. For low-power operation, bme-init-sleep may be used instead to leave the chip in sleep mode and set-up for one-shot conversions using bme-convert.

bme-calib must be called once after bme-init or bme-init-sleep to load the chip-specific calibration values.

: bme-init ( -- nak ) \ init the bme280 into continuous mode
: bme-init-sleep ( -- nak ) \ init the bme280 into sleep mode
: bme-calib ( -- )

To read the last conversion values call bme-data and then bme-calc. The humidity is returned in 1/100th percent of relative humidity, the pressure is returned in Pascal, and the temperature is returned in 1/100th degrees celsius.

: bme-data ( -- )  \ get a sensor reading from the BME280
: bme-calc ( -- h p t )  \ convert reading to calibrated values

bme-convert performs a one-shot conversion and returns the chip to sleep mode. It returns the number of milliseconds to wait before the data can be retrieved. bme-sleep forces the chip to sleep mode. Use of the init words to wake it up again.

: bme-convert ( -- ms ) \ perform a one-shot forced reading, return ms before data is ready
: bme-sleep ( -- ) \ force bme280 to sleep

Variables

32 buffer: params  \ calibration data

Constants

The BME.ADDR constant can be defined before including this driver, to override the default I2C address of $76.

Example

bme-init .
bme-calib params 32 dump
bme-data bme-calc . . .