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 BME280 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, "~> 0.2.2"}
  ]
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.

Configuration

Depending on your hardware configuration, you may need to specify options to Bme680.start_link/2 or Bme280.start_link/2. For example, the i2c address of the sensor can be 0x76 or 0x77.

Usage with the BME680

{:ok, pid} = Bme680.start_link(i2c_address: 0x76)

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

For more information, read the API documentation.

Sensor compatibility

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)

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).

Usage with the BME280

{:ok, pid} = Bme280.start_link(i2c_address: 0x76)

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

The default setting has been tested on the HiLetgo BME280.

Acknowledgements

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