← Work/BLE Hardware · Mobile Credential · 2025–2026
BLE Access Control
A phone that opens doors over Bluetooth Low Energy.
A Flutter mobile credential for a BLE relay controller: scan for the device, connect, resolve the GATT command characteristic and write two bytes to fire the lock. Native BLE clients in Kotlin and Swift sit behind a five-method platform channel, with access managed centrally in Firestore.
5 methods
Channel surface
2 bytes
Door command
iOS + Android
Platforms
Assigned doors with access schedules; tap to open
The problem
The client sells a relay controller that sits beside a door and switches the lock. It advertises over BLE and accepts short binary commands on a GATT characteristic. They needed a mobile credential — stand at the door, tap, the relay fires — with access managed centrally instead of with key fobs.
The outcome
One Flutter codebase driving the same relay controller from iOS and Android. connect() reports success only once a writable command characteristic is in hand, so a connected result means ready to send, not just link up.
What we built
- Flutter UI with Riverpod state; the app never touches Bluetooth directly.
- One platform channel, relay_sdk — configure, connect(timeout), triggerRelay1/2(withResponse), disconnect. That is the entire contract between Dart and native code.
- Native BLE clients on both platforms: android.bluetooth LE in Kotlin, CoreBluetooth in a standalone Swift Package on iOS.
- Discovery by advertised name prefix, with short-UUID suffix matching for firmware whose 128-bit base was not yet fixed.
- Firestore decides who may open which door — single-use activation codes, per-user assignments and schedules, streamed live to the app.
Architecture — Flutter, platform channel, native BLE clients
Stack
Next project
NafaPay →