From c395d4e3b00589d85f965cbdb72627426db4b857 Mon Sep 17 00:00:00 2001 From: mikkeli Date: Thu, 8 Oct 2026 09:58:51 +0900 Subject: [PATCH] Architecture: note the stale boot clock and the metered povo SIM 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 --- docs/ARCHITECTURE.md | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md index 047f2d3..86ca2a5 100644 --- a/docs/ARCHITECTURE.md +++ b/docs/ARCHITECTURE.md @@ -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 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. +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 [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 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 -is not a sensible transport for a multi-gigabyte tile set. Gate the sync on a +They reach the car by `rsync` **over the LAN only, never over LTE** — the metered +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 -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 justify anything more.