[Tecnologic]

Phase W6 of docs/web_plan.md, with the hardware decided on 2026-10-25: the MCP2518FD CAN FD HAT. For Wi-Fi, the Pi joins a known network when it is in range, else it opens its own access point. On request, the Wi-Fi can be set in the web app.

Changes

• scripts/pi-setup.sh (Raspberry Pi OS 64-bit, Bookworm or later; run as root):

  • SPI and dtoverlay=mcp251xfd,<spi>,oscillator=<Hz>,interrupt=<GPIO> in config.txt, in a marked block that a second run replaces;
  • can0 by systemd-networkd: 1 Mbit/s, CAN FD without bit rate switch, restart after a bus-off;
  • cypilot in /opt/cypilot for a system user cypilot; the DSDL and the register description file are fetched during setup, because the cart is offline;
  • cypilot.service: cypilot-ctl -i socketcan:can0 serve --host 0.0.0.0 --port 80, Restart=always, CAP_NET_BIND_SERVICE. The PIN, the runs directory, the cache and CYPILOT_WIFI=1 are in /etc/cypilot/cypilot.env;
  • Wi-Fi: a NetworkManager hotspot cypilot-ap that does not autoconnect. cypilot-wifi-fallback.service opens it when no known Wi-Fi has connected within 45 s of the boot (--no-ap for none);
  • a polkit rule lets the user cypilot use NetworkManager, for the Wi-Fi view;
  • a second run keeps the PIN, and keeps the access point key as the web app last set it;
  • the host name for http://<name>.local (avahi);
  • --dry-run --root DIR writes the files under DIR and prints the commands.

• Wi-Fi in the web app (src/cypilot/wifi.py, serve --wifi or $CYPILOT_WIFI=1):

  • the current network and address, scan, the known networks;
  • join a network (saved as known), forget one;
  • the access point's SSID and key, and open it now.

  nmcli runs with argument lists, never a shell. Reading is open; changes need the control lease. If joining fails while the access point was up, the access point is opened again, so the cart is never left without a network. The view appears only when the server manages the Wi-Fi.

• serve --pin defaults to $CYPILOT_PIN.

• scripts/load_test.py: demo devices or a real bus, a recording run, and browsers showing every subject of every node. Locally, 4 demo devices and 2 browsers: about 30 % of one core, status median 47 ms, 155 frames/s recorded.

• Scope (from CI): in a multi-node capture, once the trigger node has its capture, the other nodes get 2 s plus twice the capture's length. One that missed the trigger event then fails with "node N did not trigger on the trigger event of node M". Before, it waited the whole capture timeout (30 s) without a message.

• docs/pi.md covers hardware, setup, use, Wi-Fi in the web app and the load test. README, AGENTS and web_plan.md are updated; the plan marks the day on the bench as open.

Tests

• tests/unit/test_pi_setup.py, the dry run:
  • the overlay, can0, the service and the env file;
  • the polkit rule, the access point commands and the DSDL prefetch;
  • a second run keeps the PIN and the key;
  • bad options are refused.
• tests/unit/test_wifi.py with a fake nmcli (tests/fake_nmcli.py; one call at a time, the state written atomically): the terse parser, status, scan, known networks, join with the access point fallback, forget, the access point, and the API with the control lease.
• tests/browser/test_wifi_ui.py: join, forget and change the access point in Chromium; no Wi-Fi view without --wifi.
• tests/unit/test_scope.py: a follower that misses the trigger event fails within a few seconds.
• CI robustness, test code only:
  • test_web_sim uses the 1 s lease and checks the second enable;
  • the scope browser test reports the state and the message on a failure.
• shellcheck is clean.
• Locally: ruff, format and mypy clean; pytest 132 passed, 1 skipped. CI is green on all jobs.

Not testable here: the W6 acceptance test, a day on the cart bench with the drives. Nothing in this PR has run on a real Pi with NetworkManager yet.

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