Trouble displaying Scenic UI on RPI3 with original 7" touch display

Nerves Forum Nerves Questions / Help
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1

Hi all,

I’m coming to Nerves with considerable Elixir experience but very little hardware experience. I’m trying to use Scenic to display a UI on my Raspberry Pi 3 Model B v1.2 using the original 7" touch display, connected via ribbon cable and powered via the GPIO pins.

I’m able to build firmware and push it to the device, and the IEx console displays on the touch display and works great. I’m also able to run mix scenic.run with MIX_TARGET=host to preview my Scenic UI on my development machine with no problem. However, I can’t get anything to display on the touch display other than the IEx console.

My configuration is as follows (truncated for brevity):

# mix.exs
defmodule HelloNerves.MixProject do
  # ...

  def project do
    [
      app: @app,
      version: @version,
      elixir: "~> 1.18",
      archives: [nerves_bootstrap: "~> 1.13"],
      start_permanent: Mix.env() == :prod,
      deps: deps(),
      releases: [{@app, release()}],
      preferred_cli_target: [run: :host, test: :host]
    ]
  end

  def application do
    [
      extra_applications: [:logger, :runtime_tools, :scenic],
      mod: {HelloNerves.Application, []}
    ]
  end

  defp deps do
    [
      # Dependencies for all targets
      {:nerves, "~> 1.10", runtime: false},
      {:shoehorn, "~> 0.9.1"},
      {:ring_logger, "~> 0.11.0"},
      {:toolshed, "~> 0.4.0"},

      # Allow Nerves.Runtime on host to support development, testing and CI.
      # See config/host.exs for usage.
      {:nerves_runtime, "~> 0.13.0"},

      # Dependencies for all targets except :host
      {:nerves_pack, "~> 0.7.1", targets: @all_targets},
      {:vintage_net_wifi, "~> 0.12", targets: @all_targets},
      # ...
      {:nerves_system_rpi3, "~> 1.24", runtime: false, targets: :rpi3},
      # ...
      {:scenic, "~> 0.11.2", override: true},
      # For local development
      {:scenic_driver_local, "~> 0.11.0-beta.0", targets: :host},
      # For Raspberry Pi rendering
      {:scenic_driver_nerves_rpi,
       git: "git@github.com:boydm/scenic_driver_nerves_rpi.git",
       branch: "v0.11",
       targets: @all_targets},
      # For Raspberry Pi touch input
      {:scenic_driver_nerves_touch,
       git: "git@github.com:boydm/scenic_driver_nerves_touch.git",
       branch: "v0.11",
       targets: @all_targets}
    ]
  end

  def release do
    [
      overwrite: true,
      # Erlang distribution is not started automatically.
      # See https://hexdocs.pm/nerves_pack/readme.html#erlang-distribution
      cookie: "#{@app}_cookie",
      include_erts: &Nerves.Release.erts/0,
      steps: [&Nerves.Release.init/1, :assemble],
      strip_beams: Mix.env() == :prod or [keep: ["Docs"]]
    ]
  end
end

# target.exs
config :hello_nerves, :viewport, %{
  size: {800, 480},
  theme: :dark,
  default_scene: HelloNerves.Scene.Home,
  drivers: [
    [
      module: Scenic.Driver.Nerves.Rpi,
      name: :rpi_driver,
      debug: true
    ],
    [
      module: Scenic.Driver.Nerves.Touch,
      name: :touch_driver,
      device: "raspberrypi-ts",
      calibration: {{1, 0, 0}, {0, 1, 0}}
    ]
  ]
}

# application.ex
defmodule HelloNerves.Application do
  use Application

  require Logger

  @impl true
  def start(_type, _args) do
    Logger.info("Waiting for 1 second to allow touch device to be ready")
    Process.sleep(1000)
    Logger.info("Starting HelloNerves application")
    viewport_config = Application.get_env(:hello_nerves, :viewport)

    children =
      [
        HelloNerves.PubSub.Supervisor,
        {Scenic, [viewport_config]}
      ]

    opts = [strategy: :one_for_one, name: HelloNerves.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

If useful, here are the logs: ringlogger_next.txt · GitHub

I also have some Logger.info calls in my HelloNerves.Scene.Home.init function, and I can see that they’re being called, and I can verify that the Scenic application is running — I just don’t get any UI on the device other than the IEx console.

I’m hoping there’s something simple I’m missing, and any help is very much appreciated!

2

Hi there! :waving_hand:

I see a couple things that could cause issues with your setup. You can remove scenic_driver_nerves_rpi from your mix.exs since scenic_driver local supplants the RPI-specific driver entirely.

And similarly you can remove the two drivers you have in your config, and instead just include scenic_driver_local:

  drivers: [
    [
      module: Scenic.Driver.Local
    ]
  ]

I think that’s likely the problem, i.e. scenic_driver_local isn’t running at all, hence nothing is displaying.

I haven’t tested it recently, but GitHub - ScenicFramework/scenic_nerves_starter should serve as a good starting point for combining Scenic and Nerves. Although I’d really like to create an Igniter-based installer at some point.

I hope that helps you get started!

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