mikkeli
62c6a79f89
Brings the audio sink notes in line with project-yukart decision 12 and ORIN-RUNTIME: the wire format is chunks plus terminator from the start, and the first receiver may buffer to the terminator, so moving to streaming playback is a receiver-only change. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
99 lines
4.6 KiB
Markdown
99 lines
4.6 KiB
Markdown
---
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type: plan
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status: active
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updated: 2026-10-09
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---
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# Initial plan
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## Order
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1. MQTT client, subscribing to the retained vehicle topics. Text readout only —
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prove the contract before drawing anything.
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2. Gauges.
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3. Moving map: MapLibre against the PMTiles basemap served by the Orin, with the
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position from `yukart/gnss/fix`. No routing involved.
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4. Guidance from `yukart/nav/guidance`, once [svc-nav](gitea:yukart/svc-nav) publishes it.
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A moving map with position, heading and trace is most of the value in a car and
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needs no routing engine at all. Routing is the expensive last fraction.
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## Open
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- **Transport.** Whether the app reaches the broker directly or goes through
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`svc-gw` is decided in that repo — see its initial plan. The physical link is
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settled (below).
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- **CJK labels.** MapLibre cannot ship Japanese glyph sets as SDF ranges. Local
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font rendering must be configured, or labels will be slow or absent.
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- **Sunlight.** A typical tablet is unreadable through a windscreen in daylight.
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This is a hardware problem, but the UI should not make it worse.
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## The boundary, from this side
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Two channels with different guarantees, not one socket:
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| | Down (state) | Up (commands) |
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|---|---|---|
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| Transport | push stream | request/response |
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| Loss | tolerated; next sample supersedes | **not** tolerated; retry until acknowledged |
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| On reconnect | expect current state immediately | resend anything pending |
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This client always initiates and owns reconnection — the Orin never dials out.
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Assume the link drops constantly: cable knocked, screen off, power changes.
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## The USB link, as measured (2026-10-09)
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Tested with the actual tablet (Redmi Pad SE 8.7 4G, Android 16) against the car
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Orin. Details: [USB tablet link report](gitea:yukart/orin-nano-env-setup).
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- **Physical:** tablet USB-C → PD hub (charging from the car) → Orin's USB-C port.
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The tablet is the USB host; the Orin is a USB network gadget. The tablet picks
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**NCM** and gets `192.168.55.100`; the Orin is **`192.168.55.1`**.
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- **Android won't route over it by default.** The link has no internet, so it never
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becomes the default network while WiFi or cellular is up, and ordinary sockets go
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elsewhere. Verified: the Orin was unreachable until WiFi and cellular were off.
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The app must request the Ethernet network (`ConnectivityManager.requestNetwork`
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with `TRANSPORT_ETHERNET`) and bind its sockets to it.
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- **About 3 s blank per power change.** Cutting the hub's PD costs ~3.5 s (full
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USB detach); restoring it ~2.2 s. Ignition and cranking produce these.
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- **An asleep tablet is a dead link.** Off charger and idle, Android suspends about
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a minute after screen-off and answers nothing, while the Orin still sees the USB
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link up. The app keeps the device awake while it is the display (screen-on flag
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in the full UI; the same for any overlay widget).
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- Reconnect without user action, and expect the Orin to drop a silent client by
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heartbeat (project-yukart decision 24).
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## Session marking is worth building early
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A button that stamps an event (`indicator on`, `cold start`, `hard braking`) into
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the recording, on the same clock as the CAN frames, turns the Phase 1 manual event
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log from a notebook-and-wristwatch exercise into structured data. It is what makes
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a raw capture decodable later, and it is a Phase 1 capability that happens to live
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in this repo.
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## Mock data must look like mock data
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`svc-gw` can synthesise vehicle state without any real readings, which is how this
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app is developed with no Jetson present. The stream carries a flag when it does.
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Rendering synthetic readings indistinguishable from real ones, on a screen in a
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moving car, is a safety problem. The indication belongs on the display surface
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itself, not in a settings page or a startup log.
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## This app is the audio sink
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The tablet owns the car's aux input and is the music player, so the Orin's speech
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has to arrive here to be heard.
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- TTS arrives as an **utterance: a sequence of chunks with a terminator** over the
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reliable channel, never as one opaque file body. Streaming playback (start on
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the first chunk, append, finish on the terminator via `AudioTrack` streaming
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mode) is the target.
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- **Acceptable first version:** buffer the chunks and play on the terminator. With
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a non-streaming TTS that is a single chunk anyway. Swapping to streaming then
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changes only this receiver, not the protocol or the Orin.
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- Duck other audio with `AUDIOFOCUS_GAIN_TRANSIENT_MAY_DUCK` for the duration of
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the utterance, then release. That is what makes Spotify drop under the voice
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without either side coordinating.
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- The microphone stays on the Orin. This app never captures audio; ASR input never
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crosses the boundary.
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