app-flutter/docs/impl/plans/INITIAL.md

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Initial plan

Order

1. MQTT client, subscribing to the retained vehicle topics. Text readout only — prove the contract before drawing anything.
2. Gauges.
3. Moving map: MapLibre against the PMTiles basemap served by the Orin, with the position from yukart/gnss/fix. No routing involved.
4. Guidance from yukart/nav/guidance, once svc-nav publishes it.

A moving map with position, heading and trace is most of the value in a car and needs no routing engine at all. Routing is the expensive last fraction.

Open

• Transport. Over USB the tablet has an IP link via RNDIS, so it can reach the broker directly. Whether it should, or should go through svc-gw, is decided in that repo — see its initial plan.
• CJK labels. MapLibre cannot ship Japanese glyph sets as SDF ranges. Local font rendering must be configured, or labels will be slow or absent.
• Sunlight. A typical tablet is unreadable through a windscreen in daylight. This is a hardware problem, but the UI should not make it worse.

The boundary, from this side

Two channels with different guarantees, not one socket:

	Down (state)	Up (commands)
Transport	push stream	request/response
Loss	tolerated; next sample supersedes	not tolerated; retry until acknowledged
On reconnect	expect current state immediately	resend anything pending

This client always initiates and owns reconnection — the Orin never dials out. Assume the link drops constantly: cable knocked, screen off, WiFi lost.

Session marking is worth building early

A button that stamps an event (indicator on, cold start, hard braking) into the recording, on the same clock as the CAN frames, turns the Phase 1 manual event log from a notebook-and-wristwatch exercise into structured data. It is what makes a raw capture decodable later, and it is a Phase 1 capability that happens to live in this repo.

Mock data must look like mock data

svc-gw can synthesise vehicle state without any real readings, which is how this app is developed with no Jetson present. The stream carries a flag when it does.

Rendering synthetic readings indistinguishable from real ones, on a screen in a moving car, is a safety problem. The indication belongs on the display surface itself, not in a settings page or a startup log.

This app is the audio sink

The tablet owns the car's aux input and is the music player, so the Orin's speech has to arrive here to be heard.

• TTS arrives as discrete utterances over the reliable channel, not as a real-time stream. Receive the whole thing, then play it — no jitter buffer.
• Duck other audio with AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK for the duration of the utterance, then release. That is what makes Spotify drop under the voice without either side coordinating.
• The microphone stays on the Orin. This app never captures audio; ASR input never crosses the boundary.