Ashin Walpola
b91eb460dc
CAM codec: - Stop rejecting CAMs carrying a specialVehicleContainer. It is declared last in CamParameters, after everything this decoder reads, so buses / emergency vehicles / road-works vehicles now decode for position and kinematics instead of being dropped outright - Drop the lowFrequencyContainer parse - it extracted nothing into Cam, and its reads were only correct when no high-frequency optionals were present - Document why the 7 optional-presence bits are consumed but not acted on: UPER writes a SEQUENCE's presence bitmap up front but each field's value in declaration order, and all seven are declared after yawRate - Field widths and container ordering verified against the ETSI ASN.1 sources in the C-ITS-Parser checkout, not from memory Transmit path: - Own StationID is now a persisted random 32-bit value instead of a hardcoded 0. Receivers key on StationID to track a station across CAMs, so every unit broadcasting 0 made two MicrOBUs indistinguishable - including to this app's own detection engine - Populate longitudinalAcceleration from successive GNSS speed samples. Not from the accelerometer: CAM wants signed along-track acceleration, and the raw sensor is device-frame with gravity in it. Null outside a usable sample gap rather than a fabricated value - CAM pinger builds from live GNSS/IMU via PhoneCamBuilder instead of beaconing a hardcoded bench coordinate with speed and heading pinned to zero, so it now exercises the sensor pipeline and not just the wire. Sends nothing without a fix, and reports that rather than sitting at "Sent: 0" V2X monitor: - Received-CAM pane for the ESP32-C5 path, replacing the MQTT topic list that is permanently empty there. One row per station rather than per message - CAMs arrive at 1-10 Hz per station, so the pane is bounded by road users nearby, not by traffic rate. Nearest first, tinted by active alert level - DENM hazard pins on the live map as a warning triangle, drawn above vehicle markers. CiT One path only: the ESP32 firmware forwards BTP-B port 2001 (CAM) and drops port 2002 before it reaches the phone DenmParser uses tolerant field-name matching - the Use Case API's DENM JSON schema is not yet confirmed against real payloads.
MicrOBU Android App
Android companion app for the micrOBU; a compact V2X on-board unit developed by HAW Hamburg and consider it GmbH for vulnerable road users (cyclists, e-bike riders, pedestrians).
The app serves as the HMI for the micrOBU hardware, handling V2X message display, sensor data collection, trip recording, and OBU communication over USB-C, Wi-Fi (dev), and Bluetooth (upcoming).
Platform: Android (Kotlin) · Min SDK: 29 (Android 10) · Target SDK: 36
What it does
Real-time V2X monitoring; subscribes to the OBU's MQTT broker and displays live CAM, DENM, SPAT, MAP, and CPM messages grouped by topic with pretty-printed JSON and TX/RX badges.
DENM transmission; triggers DENM use cases (e.g. stationary vehicle warning hln-sv) on the OBU via the consider it Use Case API (v2x-uca/input/denmtrg) with a single tap.
Sensor monitoring; live readout of phone GNSS, accelerometer, gyroscope, magnetometer, and barometer alongside OBU GNSS for cross-reference.
Trip recording; foreground service records all sensor streams and detects cycling events (braking, turning, stopping) using orientation-independent signal processing. Works fully offline with no OBU connected.
Trip review; past trips displayed on an OpenStreetMap layer with detected events overlaid as coloured pins. Tap any pin for event details.
CSV export; every sensor sample written to a timestamped CSV in real time during a session. Shareable via the standard Android share sheet.
Architecture
MVVM with Repository pattern throughout. Jetpack Compose for all UI (no XML layouts). Hilt for dependency injection.
ui/screens/ Compose screens (Dashboard, V2X Monitor, Sensors, Recording, Trip History, Settings…)
ui/navigation/ Navigation graph and bottom nav bar
viewmodel/ MqttViewModel, SensorViewModel, TripRecordingViewModel
data/mqtt/ MQTT repository, Paho client, exponential-backoff reconnection
data/transport/ USB tethering detection and gateway IP resolution
data/db/ Room database (sessions, trips, detected events)
data/ SensorRepository, TripRepository, CsvExporter
domain/detection/ EventDetector, RunningStats sliding window (orientation-independent)
service/ TripRecordingService (foreground service)
Connectivity
The app uses a phased transport strategy. The MQTT client, topic subscriptions, and all UI are identical across transports; only the underlying network path changes.
| Phase | Transport | Status |
|---|---|---|
| Phase 01 | Wi-Fi | Complete |
| Phase 02 | USB-C tethering | Active |
| Phase 03 | Bluetooth BLE | Future |
The MQTT broker runs on the OBU hardware (Mosquitto 2.0.11, port 1883). In Phase 02, Android USB tethering exposes the OBU as a virtual Ethernet interface at 192.168.42.x. The app auto-detects the gateway IP on plug-in.
Key dependencies
| Library | Purpose |
|---|---|
| Jetpack Compose + Material3 | UI |
| Eclipse Paho MQTT | OBU communication |
| Room | Local database |
| Hilt | Dependency injection |
| OSMDroid | Trip review map |
| DataStore | Settings persistence |
| FusedLocationProviderClient | GNSS |
Getting started
- Open in Android Studio (Hedgehog or newer).
- Connect a device running Android 10+ (API 29).
- Build and run the
appmodule. - For Phase 02 testing: plug the phone into the OBU via USB-C, enable USB tethering on the phone, and the app will detect the interface and connect automatically. Broker IP can be overridden manually in Settings → Connection.
- For standalone trip recording: no OBU required. Go to the Record tab and tap Record.
The Wi-Fi transport (Phase 01 broker at 192.168.3.202) remains available in developer builds and can be toggled in Settings → Developer.
Project context
The micrOBU project is funded under the ZIM program (BMWK) and targets micromobility users in Hamburg. The companion app offloads processing from the compact OBU hardware to the smartphone; GNSS fusion, event detection, and future antenna coordination all run on the phone to keep the OBU lightweight and power-efficient.
V2X communication uses ITS-G5 (IEEE 802.11p / DSRC) at 5.9 GHz. The app communicates with the OBU exclusively via the consider it MQTT API v6 (processed JSON messages); no ASN.1 encoding in the app.
Owner: HAW Hamburg