orin-status docs: README, plan (sources, UPS estimate)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

docs/impl/plans/INITIAL.md

@@ -1,7 +1,7 @@
 ---
 type: plan
 status: active
-updated: 2026-10-09
+updated: 2026-10-12
 ---
 # Initial plan
 
@@ -16,6 +16,9 @@ updated: 2026-10-09
    Phase 3; MQTT at ~890 frames/s is still unproven).
 4. `decoder` — frames to named signals via the DBC in `contracts`.
 
+Alongside: **`orin-status`** — in place (2026-10-12), the first publisher on the
+bus. Below.
+
 ## Recorder
 
 Reads SocketCAN and gpsd directly. It is tier 1, and the broker is a single point
@@ -106,3 +109,38 @@ enough to time individual frames against position.
   workstation while the development Orin is offline; `check-glibc.sh` gates it.
 - **Copy-off.** Recordings stay on the car until the parked-at-home step in the
   power plan, or a manual `rsync`.
+
+## orin-status
+
+The Orin's own health as envelopes on `yukart/host/<signal>`, retained, once a
+second; names and units from contracts `signals.json` (source `host`). Tier 2,
+ordered after the broker only.
+
+| Group | Source |
+|---|---|
+| Temperatures | thermal zones `cpu`, `gpu`, `soc*` (hottest), `tj`; the `cv*` zones read EAGAIN while the vision accelerators are off and are skipped |
+| Load and memory | `/proc/stat`, the GPU's `load` (tenths of a percent), `/proc/meminfo` (one pool for CPU and GPU) |
+| Power and fan | onboard INA3221 `VDD_IN`; `pwm_tach` |
+| Network | `/sys/class/net` counters → kbit/s; WiFi level from `/proc/net/wireless`; the modem from `mmcli -m any -J` every 5 s on its own thread; the tablet link is carrier on `usb0`/`usb1`, counted on `l4tbr0` |
+| UPS | INA219 on `/dev/i2c-7` `0x41`, below |
+
+- A reading that fails is not published. Its retained value ages and `svc-gw`
+  shows it stale.
+- Service state on `yukart/system/orin-status`: `ready`, or `degraded` with the
+  failed sources; last will `stopping`.
+
+### UPS battery
+
+- **Read-only.** Only register pointers are ever written; the INA219 stays at its
+  power-on configuration. Current is shunt voltage (10 µV per bit) over 0.01 Ω
+  (Waveshare's demo code), positive when charging. Bus voltage is 4 mV per bit.
+- **State:** `charging` above +50 mA, `discharging` below −50 mA (on battery:
+  input lost), `idle` between.
+- **Charge** is an estimate from a 21700 resting-voltage table per cell, the
+  reading corrected by the pack's I·R drop (0.15 Ω, a rough figure) and smoothed.
+  Waveshare's demo maps 9.0–12.6 V linearly instead, which swings with load.
+  Steadiest at rest on input power, least reliable while charging.
+- The ignition-off policy (orin-nano-env-setup `docs/impl/plans/POWER.md`) needs
+  the same readings. It should take them from here, or live here, rather than
+  open the INA219 a second time.
+