Room sensor

RoomTempHumidity

A local whole-house temperature and humidity monitor. USB-powered room sensors send measurements over Thread to a Raspberry Pi base unit, which stores history and presents a touchscreen dashboard without requiring a cloud service.

Actual Pi dashboard

Direct capture of the running Pi display on 2026-10-11. This is the live-mode application with one reporting prototype sensor, not simulated data. Readings and freshness reflect the capture time.

Design summary

flowchart LR
  S["USB room node<br/>SHT40 + nRF54L15"] -->|"Thread IPv6 / CoAP JSON"| R["nRF52840 DK<br/>RCP"]
  R -->|"Spinel / USB serial<br/>115200 RTS/CTS"| O["Pi 5<br/>OpenThread Border Router"]
  O --> C["Python collector<br/>aiocoap + SQLite"]
  C -->|"Loopback HTTP"| D["Browser kiosk<br/>Touch Display 2"]

• Sensors: SHT40 measures temperature and relative humidity. nRF54L15 firmware uses Zephyr and OpenThread, samples every minute and sends confirmable CoAP POSTs. Random boot IDs and sequence numbers support duplicate/replay handling. Continuous USB power permits an always-listening Thread router role.
• Base radio: pinned OpenThread RCP firmware on an nRF52840 DK connects over Spinel/UART through USB serial. It is separate from the sensor-node application.
• Networking: OTBR runs on the Pi 5. Recorded deployment limits forwarding to the intended local IPv6 LAN; IPv4 forwarding, NAT64, WebGUI and REST are disabled.
• Collector/UI: Python validates readings and stores bounded SQLite history. HTML/CSS/JavaScript provides room status, history and Celsius/Fahrenheit controls. CoAP bind retries keep the local dashboard available while a Thread address is missing. The Touch Display 2 presents the landscape browser/kiosk UI.
• Protocol: Thread + IPv6 + CoAP.

Sensor hardware

Enclosure A2	Populated PCB A3 — angled 3D view

The enclosure is a native OpenSCAD render. The populated PCB is a native KiCad 3D render of the unchanged A3 layout and its 16 component placements. Package models show nominal geometry; the radio module uses a simplified dimension-based body/shield. Neither image proves assembled hardware qualification.

The working prototype uses an nRF54L15 DK and SHT40 breakout. The custom 45 × 55 mm PCB uses Raytac AN54LQ-P15 and SHT40; A3 changes the regulator to LT1761IS5-3.3#TRMPBF. Custom-board bring-up, printed fit, RF performance and thermal bias remain unqualified. A3 is quote/DFM only, not production/purchase approval.

Repository layout

Canonical workspace: C:\GIT\RoomTempHumidity. Future tasks should read AGENTS.md and migration notes.

Technologies and methodology

Sensor firmware uses C, Nordic nRF Connect SDK v3.2.1, Zephyr and OpenThread. RCP and OTBR use separate immutable upstream commits. OTBR's documented historical build uses Debug after optimized builds failed a compiler diagnostic; warning and runtime compatibility checks were retained.

The Pi application uses Python 3.11+, aiocoap, SQLite and HTML/CSS/JavaScript. Mechanical design uses parametric OpenSCAD (sensor) and CadQuery (base case), static dimension checks and independent STL topology checks. PCB work uses native KiCad schematic/layout, project-local libraries, ERC/DRC and independent manufacturing-file audits.

Source, protocol fixtures and validation limits are preserved separately from local deployment configuration. Historical hardware success is distinguished from checks rerun on this migrated snapshot:

Getting started and limits

Use the application preview, sensor build reference, RCP reference and OTBR notes. Install tools outside the repository. Real room mappings, collector addresses and commissioning credentials belong in local ignored configuration.

This is an engineering source snapshot, not a turnkey OS image or production release. Site-specific OTBR service/firewall/rollback files, full historical quotation archives and vendor 3D model bundles are omitted. See dependency limits, image provenance and licensing notice. The base-unit enclosure Revision C digital design is complete; insert, cable, slicer and physical checks remain outstanding. See its assembly and print checklist.