Download the exact 24×20×4.24mm board model (STP/CAD files) from wiki.dfrobot.com/sen0663 → Downloadable Resources. Essential before any enclosure work. Owner: Benj Due: 2026-09-11

Design enclosure around the 24×20×4.24mm SEN0663 footprint. Critical: open aperture above the lens (see §5.1 of brief). Mock both chest-clip and strap-mount orientations. Depends on: Download SEN0663 STP/CAD files (#1) Owner: Benj Due: 2026-09-18

Create nRF52840 project; bring in DFRobot_BMV080 Arduino lib (github.com/DFRobot/DFRobot_BMV080); stub I2C at address 0x57; BLE service + PM2.5 characteristic skeleton. Owner: Benj Due: 2026-09-18

RGB LED: green→yellow→orange→red based on WHO 15 µg/m³ guideline / 25–35 µg/m³ warn band. Firmware must enforce the mandatory 10s stabilisation wait before trusting or displaying readings. Depends on: nRF52840 project setup (#3) Owner: Benj Due: 2026-09-18

Order 2× DFRobot Fermion BMV080 (SKU SEN0663) direct from DFRobot. One to build, one spare. Price: $29.90/unit. Also check Leobot Electronics (SA DFRobot reseller) for local stock. Funds-dependent — this is the gate for todos: Wire sensor, Wearable field test, and LiPo/battery life test. Owner: Benj

Connect 3V3/GND/SCL/SDA/INT. Run continuous-read example from DFRobot_BMV080 lib. Confirm I2C address 0x57. Respect 10s stabilisation before trusting readings. First sanity check: does proximity/obstruction behave as described in brief §5.2? Depends on: nRF52840 firmware setup (#3 & #4) + sensor order (#5) Owner: Benj

Go/no-go milestone: clip device to running shirt, move, and check readings stay valid vs a static reference. If readings are corrupted by movement/obstruction, pivot to clip-to-strap geometry (see brief §5.1). Depends on: Wire sensor + first readings (#6) Owner: Benj

Add LiPo battery and USB-C charging. Implement periodic-measurement (duty-cycle) mode. Benchmark real battery life against spec figures: 6µA sleep / 70mA active during measurement windows. Depends on: Wearable field test (#7) Owner: Benj

The existing one-pager predates the BMV080 decision and shows Plantower-era R1,000/R1,500 tiers. Rebuild around: premium slim, fanless, silent, Atmotube-price (~R3,000), half the size. Slimness must be immediately obvious in every product visual — it's the core pitch. Can run in parallel with wearable test and battery life todos. Do not use the old one-pager for any pitch. Owner: Benj