spaxel/PROGRESS.md

Spaxel Implementation Progress

Phase 1 — Foundation

Goal: Bare-minimum loop from ESP32 to browser. Zero-config with passive radar and mDNS from day one.

Status

Item	Status	Notes
ESP32 firmware skeleton	Done	See iteration 2 below
Passive radar support	Done	BSSID filter in csi.c
BLE scanning	Done	Core 0 concurrent with WiFi
Mothership WebSocket ingestion	Done	See iteration 1 below
Dashboard skeleton	Not started
Docker packaging	Not started

Iteration Log

Iteration 2 — 2026-03-26

Completed: ESP32-S3 firmware skeleton

Implemented the full ESP32 firmware in ESP-IDF C with:

• Project structure: Standard ESP-IDF layout with firmware/ root

  • Top-level CMakeLists.txt, sdkconfig.defaults, partitions.csv (factory + OTA slots)
  • main/ component with 5 source modules

• State machine (main.c): 7-state node lifecycle

  • BOOT → WIFI_CONNECTING → MOTHERSHIP_DISCOVERY → CONNECTED
  • Degraded states: WIFI_LOST, MOTHERSHIP_UNAVAILABLE, CAPTIVE_PORTAL
  • Exponential backoff on WiFi failures (1s → 30s max)
  • 10-failure threshold before captive portal

• WiFi module (wifi.c/h):

  • STA connection with exponential backoff
  • mDNS discovery for _spaxel._tcp.local with fallback to cached IP
  • Captive portal AP mode (spaxel-XXXX) with HTTP config page
  • Event-driven connection state via FreeRTOS event group

• WebSocket client (websocket.c/h):

  • Bidirectional communication on single connection
  • Binary CSI frame transmission (24-byte header + I/Q payload)
  • JSON message handling: hello, health, ble, ota_status upstream
  • Downstream command parsing: role, config, ota, reboot, identify, reject
  • OTA download task with progress reporting and automatic reboot

• CSI capture (csi.c/h):

  • WiFi promiscuous mode with CSI callback
  • Queue-based processing (32-frame buffer)
  • Passive mode BSSID filtering for radar
  • On-device amplitude variance tracking for motion hints (Welford's algorithm)
  • TX task for active probing

• BLE scanner (ble.c/h):

  • Passive BLE scanning on Core 0 (concurrent with WiFi)
  • Device cache (60 entries) with name and manufacturer data parsing
  • 5-second reporting interval via WebSocket
  • GAP event handling for advertisement processing

• NVS persistence: Full schema with 15 keys

  • WiFi credentials, node ID/token, mothership config
  • Role/rate persistence for degraded mode operation
  • Schema versioning for migration support

Files created:

firmware/
├── CMakeLists.txt
├── sdkconfig.defaults
├── partitions.csv
└── main/
    ├── CMakeLists.txt
    ├── spaxel.h
    ├── main.c
    ├── wifi.h / wifi.c
    ├── websocket.h / websocket.c
    ├── csi.h / csi.c
    └── ble.h / ble.c

Remaining for Phase 1:

• Dashboard skeleton (HTML/JS + Three.js)
• Docker packaging

Iteration 1 — 2026-03-26

Completed: Mothership WebSocket ingestion server

Implemented the core ingestion server in Go with:

• Module structure: mothership/ with cmd/mothership/ entrypoint and internal/ingestion/ package
• WebSocket endpoint: /ws/node accepts bidirectional connections from ESP32 nodes
• Binary frame parsing: 24-byte header + variable payload, per spec in plan.md
  • Validation: min/max length, payload size match, channel validity (1-14), subcarrier limit (128)
  • Malformed frame tracking with warn/close thresholds (100/1000 per minute)
• JSON message handling: Parses hello, health, ble, motion_hint, ota_status
• Per-link ring buffers: 256-sample circular buffers keyed by nodeMAC:peerMAC
• Connection lifecycle: Node registration via hello, ping/pong keepalive (30s/60s), graceful shutdown
• mDNS advertisement: _spaxel._tcp.local via github.com/hashicorp/mdns
• Role/config push: Sends initial rx role and 20 Hz config on connect
• Health endpoint: GET /healthz returns {"status":"ok","version":"..."}

Dependencies used:

• github.com/go-chi/chi — HTTP routing
• github.com/gorilla/websocket — WebSocket server
• github.com/hashicorp/mdns — mDNS advertisement

Tests: 22 tests covering frame parsing, JSON messages, and ring buffer operations. All pass.

Files created:

mothership/
├── cmd/mothership/main.go
├── go.mod
├── go.sum
└── internal/ingestion/
    ├── frame.go
    ├── frame_test.go
    ├── message.go
    ├── message_test.go
    ├── ring.go
    ├── ring_test.go
    └── server.go