Just a quick update:

The project is called homex and can be found at GitHub - kevinschweikert/homex: A bridge between Elixir and Home Assistant · GitHub .

There is a nerves example project at GitHub - kevinschweikert/Homex-Nerves-Example: An example project using Homex in Nerves · GitHub

I’m currenlty waiting on a new Hex release of the emqtt library which i am using as the MQTT client.

Some sample code:

defmodule HomexDemo.TemperatureSensor do
  @moduledoc """
  A Homex.Entity for the BME680 sensors temperature values
  """

  use Homex.Entity.Sensor,
    name: "bme680 temp",
    device_class: "temperature",
    unit_of_measurement: "°C"

  def handle_timer(entity) do
    {:ok, measurements} = BMP280.measure(BME680)
    entity |> set_value(Float.round(measurements.temperature_c, 2))
  end
end

defmodule HomexDemo.Relay do
  @moduledoc """
  A Homex.Entity for a relay.
  Uses `put_private/3` and `get_private/2` to keep the i2c bus handle in state and reference it
  """

  use Homex.Entity.Switch, name: "quiick_relay"

  def handle_init(entity) do
    {:ok, bus} = Circuits.I2C.open("i2c-1")
    entity |> put_private(:bus, bus) |> set_off()
  end

  def handle_on(entity) do
    bus = entity |> get_private(:bus)
    Circuits.I2C.write!(bus, 0x18, <<0x01>>)
    entity
  end

  def handle_off(entity) do
    bus = entity |> get_private(:bus)
    Circuits.I2C.write!(bus, 0x18, <<0x00>>)
    entity
  end
end

and some pictures

SCR-20250930-ssuq1012×875 46 KB

pi640×640 73 KB

i will write an announcement post when the hex version is published. But in the meantime feel free to play around with it and give feedback!

After a bit of back and forth with @joshknz we came to the conclusion that the MQTT route would be the best to start from and see from there how the project evolves. Josh also made the point to look at Matter and see if that could be a more generic solution to make Nerves devices compatible with ecosystems like Apple HomeKit and Google Home instead of only Home Assistant. Home Assistant already supports Matter so that way would still be possible.

Inspiration came from GitHub - mtrudel/hap: A HomeKit Accessory Protocol (HAP) Implementation for Elixir · GitHub

We also talked about a more GenServer-ish implementation which could look like this:

defmodule LivingRoomTemo do
  use HomeAssistantNerves.Sensor,
    name: "Living Room Temperature",
    unit_of_measurement: "°C",
    device_class: :temperature,
    update_interval: Duration.new(seconds: 60)
    
  def handle_state(_temp) do
    YourTempSensor.read()
  end
end
  
defmodule Garage do
  use HomeAssistantNerves.Switch,
    name: "Garage Light"
    
  def handle_state(_state) do
    GPIO.read(pin)
  end

  def handle_command(:toggle, _state) do
    GPIO.write(pin, !state)
  end
end

The plan is to create a Repo and go from there and explore ideas. Will post the link here as soon as we have something to show!

It’s released! homex | Hex