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Rebuild the framework with smaller TLS buffers (ADR 0006)

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custom_sdkconfig makes pioarduino regenerate the ESP-IDF libraries:
asymmetric TLS buffers (16 KB in, 4 KB out) and dynamic buffers that
free handshake-only data once connected. The rebuild also follows the
board: no PSRAM, 8 MB flash. The project now carries the partition
table the hybrid build needs (identical to the framework's: the app
slots must not move under updates over the air). Generated files are
ignored.

Debug Build, GNSS on, IRC on TLS: 78 KB free and a 59 KB low (M2 began
at 31 KB and 12.6 KB; the floor is 40 KB). The full stress set passes
on it: refused installs over Wi-Fi and from SD, put/get, screenshot,
core dump decode, Probation; under all of it at once, the low is 46 KB.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT
This commit is contained in:
twisla
2026-10-04 23:32:29 +02:00
co-authored by Claude Opus 5.5
parent 4e439410cd
commit fff28af961
6 changed files with 54 additions and 2 deletions
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docs/milestones/M2.md
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# M2 — GNSS
**Status:** steps 1–6 done on the device (branch `m2`). Open: the heap floor during a TLS handshake (below).
**Status:** done on the device (branch `m2`): every "Done when" item below is met.
## Measured
- **Cold start** (`$PCAS10,2`) to a 3D Fix, by a window: **73 s**, 5 satellites used of 8 in view. A restart of the ESP32 alone keeps the receiver's Fix (the Cap stays powered).
- By a window: 3D Fix from GPS, GLONASS, Galileo and BeiDou, up to 14 of 17 satellites used, HDOP 1.0–1.3.
- **Heap, Debug Build, GNSS on:** with IRC on TLS, first 33 KB free and a 12.6 KB low (floor 40 KB; v0.2.1 had a 79 KB low). Not a GNSS cost: the OTA and Debug Build work added task stacks, a console ring, serial buffers, mDNS and two TCP servers. **Trimmed by measurement:** each task's peak stack was measured through its worst case (an ECDSA-checked install over Wi-Fi and from SD, get/put, a core dump fetch, an IRC TLS handshake), then stacks were set to peak plus about 2 KB: loop 8→6 KB, update 8→5, storage 10→6, irc 8→6; the console ring 6→4 KB, serial TX 2→1 KB, GNSS UART 1 KB→512 B. **After:** 46 KB free with IRC connected, an 18 KB low. The steady state clears the floor; the TLS handshake peak doesn't yet. Next candidates: mbedTLS dynamic buffers (custom sdkconfig), one network task for the update and debug listeners, mDNS on demand.
- **Heap, Debug Build, GNSS on, IRC on TLS** (floor 40 KB; v0.2.1 had a 79 KB low):
| | Free | Lowest |
|---|---|---|
| Start of M2 | 31 KB | 12.6 KB |
| Stacks and buffers trimmed by measurement | 46 KB | 18 KB |
| mDNS removed | 54 KB | 34 KB |
| Framework rebuilt with smaller TLS buffers (ADR 0006) | **78 KB** | **59 KB** |
Under the heaviest combined load measured (IRC, two refused installs, a 1.6 MB put and get), the low is 46 KB. The cost had come mostly from the OTA and Debug Build work, not GNSS. Stacks were set to measured peak plus about 2 KB (loop 6 KB, update 5, storage 6, irc 6); after a TLS handshake the irc task has 1.7 KB left. IRC can now be stopped by hand (`/quit` in any state, `irc stop`), which frees its TLS memory.
**Goal:** the device knows where it is and what time it is without a network: a GNSS Service in the background, a GNSS App with the position and a sky view of the satellites, the clock set from satellites when there's no NTP, and Tracks recorded to the SD card.