elixir_bme680 v0.2.0 Bme680 View Source

elixir_bme680 provides a high level abstraction to interface with the BME680 environmental sensor on Linux platforms.

Link to this section Summary

Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor

init(list)

Invoked when the server is started. start_link/3 or start/3 will block until it returns

measure(pid)

Perform a measurement on the BME680 sensor and synchronously return it

measure_async(pid, send_to)

Perform a measurement on the BME680 sensor and asynchronously send the result as a message to the pid in send_to

start_link(bme_opts \\ [], opts \\ [])

Starts and links the Bme680 GenServer

stop(pid)

Gracefully stops the Bme680 GenServer

Link to this section Functions

child_spec(init_arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

init(list)

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

init_arg is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state}, except that it also sets a timeout. See the “Timeouts” section in the module documentation for more information.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

The GenServer is disabled by configuration but might be enabled later.
An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

measure(pid)

measure(GenServer.server()) :: %Bme680.Measurement{
  gas_resistance: integer() | nil,
  humidity: float(),
  pressure: float(),
  temperature: float()
}

Perform a measurement on the BME680 sensor and synchronously return it

Measurements are structs like:

%Bme680.Measurement{
  temperature: 21.74,
  pressure: 1090.52,
  humidity: 45.32,
  gas_resistance: 10235
}

measure_async(pid, send_to)

measure_async(GenServer.server(), pid()) :: :ok

Perform a measurement on the BME680 sensor and asynchronously send the result as a message to the pid in send_to

start_link(bme_opts \\ [], opts \\ [])

start_link(
  [
    i2c_device_number: integer(),
    i2c_address: 118 | 119,
    temperature_offset: non_neg_integer()
  ],
  [term()]
) :: GenServer.on_start()

Starts and links the Bme680 GenServer.

Options:

i2c_device_number is the number of the i2c device, e.g. 1 for /dev/i2c-1
i2c_address i2c address of the sensor. It can be only 0x76 or 0x77
temperature_offset is an offset, in degrees Celsius, that will be subtracted to temperature measurements in order to compensate for the internal heating of the device. It’s typically around 4 or 5 degrees, and also affects relative humidity calculations

stop(pid)

stop(GenServer.server()) :: :ok

Gracefully stops the Bme680 GenServer.