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Architecture: note the stale boot clock and the metered povo SIM

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The car unit has no RTC battery, so before NTP the clock sits near the
last shutdown time; that is the case the two-clock envelope exists for.
The LTE SIM is povo, not an IoT SIM, and its connection now carries
the metered flag the map-sync guard relies on.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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mikkeli
2026-10-08 09:58:51 +09:00
parent f05fda71ee
commit c395d4e3b0
1 changed files with 6 additions and 3 deletions
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@@ -84,6 +84,8 @@ Payloads: a self-describing JSON envelope for decoded signals; compact binary fo
Every envelope carries **two clocks**. `monotonic` is authoritative for ordering Every envelope carries **two clocks**. `monotonic` is authoritative for ordering
and intervals; `timestamp` is the absolute reference and may step, since the car and intervals; `timestamp` is the absolute reference and may step, since the car
boots without network and NTP corrects the clock once LTE connects mid-drive. boots without network and NTP corrects the clock once LTE connects mid-drive.
The car unit has no RTC battery, so until then the clock sits at roughly the
last shutdown time — offset by however long the car was parked.
Topic names, payload schemas and the signal registry live in Topic names, payload schemas and the signal registry live in
[contracts](gitea:yukart/contracts). [contracts](gitea:yukart/contracts).
@@ -259,10 +261,11 @@ They are never committed. `tool-mapmint` holds the scripts that fetch and build
them, plus a report of each build's provenance; `svc-nav` consumes the output. The them, plus a report of each build's provenance; `svc-nav` consumes the output. The
artifacts themselves live outside git and never touch the workstation-side repo. artifacts themselves live outside git and never touch the workstation-side repo.
They reach the car by `rsync` **over the LAN only, never over LTE** — the IoT SIM They reach the car by `rsync` **over the LAN only, never over LTE** — the metered
is not a sensible transport for a multi-gigabyte tile set. Gate the sync on a povo SIM is not a sensible transport for a multi-gigabyte tile set. Gate the sync on a
reachable LAN target rather than on an SSID, so the check validates the thing it reachable LAN target rather than on an SSID, so the check validates the thing it
actually needs, and treat NetworkManager's metered flag as a second guard. actually needs, and treat NetworkManager's metered flag as a second guard (set on the `povo`
connection).
Cadence is quarterly or on annoyance; road geometry does not move fast enough to Cadence is quarterly or on annoyance; road geometry does not move fast enough to
justify anything more. justify anything more.