Real-time meeting-room availability, sensed by radar and shown right on the door.
A 24GHz radar sensor in each room detects human presence — that a person is there, never who (no cameras, no microphones) — and reports to a Cloudflare Workers API. Two consumers read that data:
- E-ink door displays show FREE / OCCUPIED at a glance. Battery-powered, they deep-sleep and poll during office hours, running ~1–2 weeks per charge.
- A web dashboard gives a live overview of every room, plus how they're used over time (utilization, busy hours).
The outcome: walk down the hall and see which rooms are free without opening a calendar or a booking app — and see room-usage trends on the dashboard. Privacy by design: radar only knows presence, not identity.
Sensor node (Freenove ESP32 + LD2410C radar) ──POST /events──► Cloudflare
Worker (Hono)
Display node (Waveshare e-paper) ──GET /rooms/:id──► + D1
Dashboard (React SPA) ──GET /rooms─────► + static assets
Two nodes per room: a mains-powered sensor node that senses continuously, and a battery display node that deep-sleeps and polls during office hours. A single Cloudflare Worker (Hono) on D1 holds current room state plus an append-only event log and serves the dashboard (React SPA) as static assets — same origin, one URL.
firmware/sensor-node/ Freenove + LD2410C radar (PlatformIO)
firmware/display-node/ Waveshare e-paper (GxEPD2 + deep sleep)
api/ Cloudflare Worker (Hono) + D1 migrations
dashboard/ React SPA (Vite) — served by the Worker as static assets
- SETUP.md — step-by-step to stand up your own copy end to end (Cloudflare backend, dashboard, device tokens, firmware).
- PLAN.md — design, data model, API surface, and the decisions behind them.
- PRODUCTIONIZING.md — current state and what a full office-wide rollout would take (IoT Wi-Fi, display power, more pairs, Sentry- hosted dashboard, and the operational gaps in between).
- api/README.md — API endpoints, deploy & operate, tokens.
- firmware/README.md — flashing sensors & displays, board pinouts, and the battery/power gotchas.
Hackweek project — 4 rooms, 4 device kits, all provisioned and running.
- App — dashboard + API on one Worker: https://sentry-sonar-api.francesconovy.workers.dev (the dashboard is at the root path; its data only loads from an allowlisted office IP)