Nerves Emerge Demo

A small demo application built with Emerge and Solve for Nerves. It renders a simple animated UI over DRM and wires button presses into a counter controller.

Requirements

• Elixir ~> 1.19
• One of the supported Nerves targets: rpi4 or rpi5
• At least one SSH public key in ~/.ssh, required for target builds by config/target.exs

Run Locally

mix deps.get
iex -S mix

This starts the app on the host using the Wayland backend from config/host.exs.

Build Firmware

export MIX_TARGET=rpi5
mix firmware

rpi4 should also work, but it is not currently tested and may require a different drm_card value in lib/nerves_emerge_demo.ex and/or some changes to the nerves_system.

To bake WiFi settings into the firmware image with mise, put them in the git-ignored mise.local.toml before building:

[env]
NERVES_WIFI_SSID = "your-ssid"
NERVES_WIFI_PSK = "your-passphrase"
NERVES_REGULATORY_DOMAIN = "US"

Then build firmware with an explicit target:

export MIX_TARGET=rpi5
mix firmware

If you are not using mise, you can still export the vars in your shell:

export MIX_TARGET=rpi5
export NERVES_WIFI_SSID="your-ssid"
export NERVES_WIFI_PSK="your-passphrase"
export NERVES_REGULATORY_DOMAIN="US"
mix firmware

NERVES_WIFI_SSID and NERVES_WIFI_PSK are read from config/target.exs during the build. WIFI_SSID, WIFI_PSK, WIFI_COUNTRY_CODE, and WIFI_REGULATORY_DOMAIN are also accepted as fallback names. If no PSK is set, the network is treated as open.

Test

mix test

Use The App

• The viewport renders an animated background and two counter rows.
• Pressing + and - dispatches Solve events to the counter controller.
• The displayed count updates from the exposed state in NervesEmergeDemo.State.

Project Layout

lib/nerves_emerge_demo.ex is the viewport entrypoint. It mounts the app and renders the UI with Emerge.

lib/nerves_emerge_demo/state.ex defines the top-level Solve app and wires in the counter controller.

lib/nerves_emerge_demo/counter_controller.ex owns the increment and decrement event handlers.

lib/nerves_emerge_demo/application.ex starts the state process and viewport under the supervision tree.

Notes

• host mode uses the Wayland backend
• target mode uses the DRM backend
• rootfs_overlay/etc/iex.exs enables Toolshed in the target IEx session

References

• Emerge
• Solve
• Nerves

License

Licensed under the Apache License, Version 2.0. See LICENSE.