Sentinel
Autonomous Privacy-First OBD-II Distance Computation Device
Sentinel is a proprietary OBD-II hardware device developed by RUC on Rails during our early automated RUC research phase.
It was not built as a tracking device. It was built as a distance engine. It measures how far a vehicle has travelled, and nothing more.
Privacy by Architecture, Not Policy
Distance-based charging systems require cumulative distance. They do not require route reconstruction, trip timelines or behavioural profiling.
Most GPS-based systems inevitably generate continuous coordinate logs, route playback capability, location time-stamps, driving pattern metadata and centralised movement archives.
Sentinel was deliberately engineered to avoid that model entirely. Privacy was not layered on top. It was embedded into the design itself.
GPS-Based Systems Generate
Sentinel Produces
Hardware & Embedded Foundation
Sentinel is a physical OBD-II plug-in device that connects directly to a vehicle's diagnostic port. It operates as a passive interpreter of broadcast vehicle data.
The device reads vehicle signals in a strictly passive manner. It does not modify ECU parameters. It does not inject messages into the CAN bus. It does not alter vehicle behaviour.
Its function is computational only.
Fully Autonomous Edge Computation
All primary distance computation occurs on-device. Distance is calculated using structured numerical integration techniques, operating at a fixed baseline sampling interval.
No GPS Required
Distance derived mathematically from vehicle motion data rather than inferred from geographic position.
No Mobile Data
The device operates independently of cellular connectivity. Computation continues regardless of network availability.
No Cloud Dependency
Cloud infrastructure used only for UI synchronisation. The device itself remains computationally independent.
Dual-Mode Measurement System
To balance universal compatibility with high precision, Sentinel employs a dual-mode measurement architecture with automatic precision enhancement.
Baseline OBD-II Polling
In its baseline configuration, the device polls standardised vehicle speed data through OBD-II at a structured interval. This ensures broad compatibility across modern vehicle fleets and provides deterministic accumulation suitable for general use.
- Standardised OBD-II protocol
- Universal vehicle support
- Structured sampling interval
- Deterministic accumulation
Enhanced CAN Extraction
Where vehicles broadcast higher-resolution speed signals over the CAN bus, Sentinel activates an enhanced passive extraction mode. The device silently observes manufacturer-specific messages, identifying higher-frequency and higher-precision speed data.
- Passive CAN observation
- Manufacturer-specific signals
- Higher frequency sampling
- Precision enhancement
Calibration occurs transparently during normal driving. No user input is required, and no distance data is lost during the calibration phase. The system gracefully falls back to baseline mode if enhanced signals are unavailable.
Vehicle Compatibility & Precision
During internal R&D validation testing, Sentinel demonstrated broad compatibility and impressive precision across extended distance measurements.
GPS-Free Precision
Unlike GPS-based systems, Sentinel does not experience satellite drift, signal dropout distortion, multipath interference or route-based reconstruction artefacts. Performance was stable across both urban stop-start driving and sustained highway conditions.
Data Boundaries & Minimisation
Sentinel's data model was intentionally narrow. When synchronisation occurred via BLE, only accumulated unsynced meters were transmitted. There was no continuous telemetry stream and no live tracking feed.
This design enforced data minimisation structurally, rather than procedurally.
Stored on Device
Not Stored
Engineering Depth
Developing Sentinel required significant embedded engineering investment, producing a self-contained hardware device capable of autonomous, privacy-preserving distance computation independent of satellite systems.
Real-Time Firmware
Firmware development in C using ESP-IDF with FreeRTOS for deterministic task scheduling and real-time processing guarantees.
CAN Frame Parsing
Low-level CAN frame parsing and interpretation operating at 500kbps to extract vehicle speed signals from broadcast data.
Numerical Integration
Deterministic numerical integration techniques for converting sampled speed data into precise cumulative distance measurements.
BLE Communication
BLE 5.0 service implementation with structured handshake protocols for secure data synchronisation with companion applications.
Flash Persistence
Non-volatile flash memory management ensuring distance data survives power cycles, vehicle shutdowns and unexpected interruptions.
Sync Safeguards
Sequence-based synchronisation safeguards preventing duplicate or missing distance records across BLE communication sessions.
Strategic Position
Sentinel remains an internal R&D asset within the RUC on Rails technology portfolio. While our current focus is digital transaction infrastructure and retail distribution systems, Sentinel demonstrates our ability to engineer hardware-level solutions where precision and privacy are critical.
Privacy-Preserving Distance Computation
Sentinel demonstrates our ability to engineer hardware-level solutions where precision and privacy are critical, measuring distance without creating a surveillance layer.