What it is

An end-to-end air-quality system: the sensor measures, the app collects over BLE, and the API stores and serves the data.

What I built

All three layers: Arduino C++ firmware on nRF52840, an Android app with biometric authentication, and a dockerised Node.js + PostgreSQL backend.

How

From soldering to deploy: hardware, BLE protocol, app and server built as one product, not loose parts.