mikkeli
c1ffba08fb
Tested against the car Orin: the tablet is USB host to the Orin's NCM gadget (192.168.55.1). Android routes app traffic over it only when it is the default network, so the app must bind to TRANSPORT_ETHERNET. PD changes cost ~3 s, and an idle tablet off charger sleeps and goes silent, so the app keeps the device awake. Two guidelines follow. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
94 lines
4.3 KiB
Markdown
94 lines
4.3 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 **discrete utterances** over the reliable channel, not as a
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real-time stream. Receive the whole thing, then play it — no jitter buffer.
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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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