Elixir Bme680

An Elixir library to interface with the BME680 and BME280 environmental sensors. The BME680 provides measurements of temperature, pressure, humidity, and gas resistance (which is a proxy of indoor air quality). The ME680 is a lower cost device that only provides measurements of temperature, pressure, humidity.

Installation

The package can be installed by adding elixir_bme680 to your list of dependencies in mix.exs:

def deps do
  [
    {:elixir_bme680, "~> 0.1.4"}
  ]
end

The Linux I2C driver needs to be installed for this library to work (e.g. libi2c-dev on Debian). If using Nerves, the driver should already be installed by default.

Usage with Bme680

{:ok, pid} = Bme680.start_link()

measurement = Bme680.measure(pid)

# Measurement is like:
#
#   %Bme680.Measurement{
#     temperature: 21.74,
#     pressure: 1090.52,
#     humidity: 45.32,
#     gas_resistance: 10235
#   }
#
# Where temperature is in degrees Celsius, pressure in hPa, humidity in %
# relative humidity, and gas_resistance in Ohm

Usage with Bme280

{:ok, pid} = Bme280.start_link()

measurement = Bme280.measure(pid)

# Measurement is like:
#
#   %Bme280.Measurement{
#     temperature: 21.74,
#     pressure: 30.52,
#     humidity: 45.32
#   }
#
# Where temperature is in degrees Celsius, pressure in inHg, humidity in %
# relative humidity

For more information, read the API documentation.

Sensor compatibility BME680

The default setting has been tested on the Pimoroni BME680. The Adafruit BME680 requires using a different i2c address. For the Adafruit, pass in the i2c_address option with value 0x77 as follows:

Bme680.start_link(i2c_address: 0x77)

Sensor compatibility BME280

The default setting has been tested on the HiLetgo BME280.

Note on gas resistance sensor warm up on the BME680

Note that, due to the nature of the BME680 gas resistance sensor, the gas resistance measurement needs a warm-up in order to give stable measurements. One possible strategy is to perform continuous meaurements in a loop until the value stabilizes. That might take from a few seconds to several minutes (or more when the sensor is brand new).

Acknowledgements

This project contains low-level code from the BME680 driver by Bosch and the BME280 driver by Bosch