beamicom_ei

Beamicom EI

beamicom_ei is an implementation of the EI input protocol over a Unix-domain socket. It provides a server that publishes one or two virtual controllers, a client that sends complete button state, and an optional SDL adapter for physical controllers.

The public modules retain the Beamicom.EI namespace:

• Beamicom.EI.Server accepts EI clients and reports committed button changes.
• Beamicom.EI.Client connects to an EI server and sends button state.
• Beamicom.EI.Gamepad reads SDL-compatible USB and Bluetooth controllers and sends their complete state through a dedicated client.
• Beamicom.EI provides the default socket path.

Usage

Add the sibling project as a path dependency:

{:beamicom_ei, path: "../beamicom_ei"}

Start a server and connect a client:

{:ok, server} =
  Beamicom.EI.Server.start_link(
    path: Beamicom.EI.default_path(),
    on_buttons: fn port, buttons -> IO.inspect({port, buttons}) end
  )

{:ok, client} = Beamicom.EI.Client.start_link(path: Beamicom.EI.Server.path(server))
:ok = Beamicom.EI.Client.await_ready(client)
:ok = Beamicom.EI.Client.set_buttons(client, 1, [:right, :a])

{:ok, gamepad} =
  Beamicom.EI.Gamepad.start_link(
    path: Beamicom.EI.Server.path(server),
    ports: [1, 2]
  )

Both sides default to controller ports [1, 2]. Pass ports: [1] to both the server and client for a single-controller system such as Game Boy or Game Boy Color. Supported buttons are :up, :down, :left, :right, :a, :b, :x, :y, :l, :r, :select, and :start.

The server socket is created with mode 0600. Button changes are published on ei_device.frame, and disconnecting a client releases that client's held buttons.

Physical controllers

When pkg-config can find SDL2, compilation also builds the external gamepad_input Port program. No native code is loaded into the BEAM. The D-pad and left stick control direction, while SDL's standardized A/B/X/Y, shoulder, Back, and Start buttons map to the matching EI buttons.

Controllers are assigned in connection order to the requested ports. Extra controllers wait and are promoted when an assigned controller disconnects. Because the adapter is part of beamicom_ei, Scenic, V4L2, streaming, and other frontends can start it against their EI server without duplicating device handling. If SDL2 is unavailable, the project still compiles and Beamicom.EI.Gamepad.start_link/1 returns :ignore unless an explicit helper command is provided.

Tests

mix test