Pelorus — architecture record
Last Updated: April 28, 2026
Status: Living (non-normative)
1. Project
Mission
Open marine data network; CAN FD core; Rust-first reference code; reliability offshore.
Legacy Marine Data Ecosystem (LMDE)
LMDE is this project’s umbrella term for the certification-gated, mostly proprietary marine connectivity landscape—CAN fieldbuses, OEM Ethernet fabrics, and connector families that dominate recreational installs. Compared to open, sailor-owned buses, it optimizes for vendor control and program revenue. Typical drawbacks:
- Specifications and certification are very expensive—or unobtainable outright; where shared at all, access is often gated by mandatory NDAs and pay-to-play programs.
- Interoperability commonly means bridges and gateway SKUs, not one open wire format from sensor to laptop.
- Similar-looking cable plants can carry incompatible framing—looks like “marine network,” behaves like silos.
- Helm-side debuggability is weak: the interesting signal-level truth is frequently contractually or practically closed.
Pelorus does not assert bit-level compatibility with any incumbent stack.
The bulleted names below are examples of real-world commercial buses and networks that fall under the LMDE umbrella—non-exhaustive, nominative, and not normative targets for Pelorus conformance.
- NMEA 2000® — Multidrop CAN instrument network; certification-gated ecosystem for certified recreational marine electronics.
- SeaTalk NG — Raymarine NMEA-2000-class cabling and device network for integrated displays and sensors.
- SimNet — Simrad / Lowrance / B&G (Navico) CAN network for MFDs, sonar, and radar interfaces.
- SmartCraft — Mercury / MerCruiser engine and vessel digital diagnostics and data bus.
- Volvo Penta EVC — Volvo propulsion and vessel control digital network.
- Yamaha Command Link — Yamaha outboard digital instrumentation and control bus.
- RayNet — Raymarine high-speed Ethernet fabric (e.g. radar / plotter backhaul).
- Navico Ethernet — Navico-family marine Ethernet for displays, imaging, and accessories.
- Garmin Marine Network — Garmin plotter, sonar, and sensor integration fabric.
- Furuno NavNet — Furuno integrated navigation, radar, and sensor network.
- NMEA OneNet® — NMEA IPv6 / Ethernet application-layer family for high-bandwidth marine IP (parallel path to 2000-class CAN for many vendors).
Presence
- Pelorus project site — Landing page for the Pelorus open marine data network.
- Specifications repository — Source of truth for this document set; issues and changes live here.
- Seven Seas community — Project-facing brand and wider community entry point (not limited to Pelorus).
2. Problem Pelorus targets
Weaknesses of Legacy Marine Data Ecosystem that Pelorus addresses:
- Specification gate: Proprietary message catalogs; costly certification; NDAs—hard for sailors and small builders to inspect, extend, or verify independently.
- Lab-first qualification: Conformance is proven on the bench, not under years of salt spray, vibration, wet connectors, and RF-rich passages.
- Always-on drain: Without selective sleep as the norm, the suite draws continuous aggregate current even when voyage context makes much of it useless for days.
- Classical CAN ceiling: Install base is stuck at ~250 kbit/s Classical CAN and 8-byte frames; Pelorus Core uses CAN FD with up to 64-byte frames. Typical navigation/engine DCIDs still don’t need “more Mbps” as much as openness, power discipline, and behavior.
- Backbone fault domain: A linear segment is one electrical island—opens, shorts, or bad terminators can blind everything on that backbone.
- Opaque diagnostics: Little vendor-neutral tooling to capture and decode live traffic as your ship’s contract.
- Vendor islands: Optional-field gaps and proprietary extensions → cross-brand surprises and gateway-heavy rigs despite compatible cabling.
- Parallel Ethernet silos: Vendor marine Ethernet fabrics add another incompatible layer beside CAN—more cables, boxes, and translation—not one unified media plane.
- Cadence drag: Cert-gated evolution is slow next to automotive or IT stack velocity—features queue behind programs and committee cycles.
- Tooling capture: Firmware updates and deep diagnostics often depend on OEM apps, dongles, or dealer chains—not something you fully own at anchor.
3. Subsystems
Core
CAN FD fieldbus for safety-critical instrumentation and controls. Application traffic is defined by Pelorus DCIDs — the wire contracts naming payloads and semantics on the bus—with selective wake groups and M12 DeviceNet physical plant.
The rest of Pelorus stacks around Core as the authoritative source of wired device contracts; Stream and higher layers must not degrade Core when they fail.
LMDE and Pelorus Core are not same-segment‑interoperable.
Stream
Ethernet non-safety-critical layer for bandwidth-heavy traffic: M12 D-coded 100 Mbit/s, IPv6, discovery—a transport substrate, not an actuator or safety plane. Example use cases include:
- Bridge monitoring
- Engine diagnostics
- Voyage data recording
- Radar integration
- ECDIS connectivity
- AIS data sharing
- Remote vessel monitoring
- Smart sensor networks
- Autonomous navigation support
- Cybersecure marine networking
- Cloud data synchronization
- Fleet management analytics
- Real-time weather data integration
- Port communication systems
- Onboard IoT device integration
- CCTV and video surveillance streaming
- Docking and situational awareness cameras
- Passenger infotainment systems
- Distributed audio/music systems
- Crew communication and video conferencing
Core stays authoritative for safety-critical semantics.
Core → Stream: Telemetry and identity/metadata aligned with DCIDs are bridged onto Stream through the standard gateway.
Stream → Core: Reverse injection onto the Core fieldbus—anything originating on the Ethernet side toward CAN—is permitted only through a capable bidirectional gateway. Arbitrary Stream publishers must not originate traffic as Core talkers.
State
Pelorus State (when specified) coordinates priorities among publishers. Stream transports payloads; it does not replace Core as nautical truth.
Logical event → snapshot → situation → policy/intent pipeline above Core and Stream, with no fieldbus or Ethernet I/O of its own.
4. Trademarks and third-party names
Pelorus is an independent open specification. This is not legal advice; consult counsel before shipping product packaging, marketing, or certifications that cite other organizations’ brands.
The commercial networks named as examples under Legacy Marine Data Ecosystem (LMDE) — NMEA 2000®, SeaTalk NG, SimNet, SmartCraft, Volvo Penta EVC, Yamaha Command Link, RayNet, Navico Ethernet, Garmin Marine Network, Furuno NavNet, NMEA OneNet®, and the vendor / house marks referenced in those lines (including Raymarine, Navico, Simrad, Lowrance, B&G, Garmin, Furuno, Volvo Penta, Yamaha, Mercury, MerCruiser) — are third-party names cited nominatively to identify real-world buses and fabrics; rights belong to their respective owners, not Pelorus.
Practical editorial rules for this repository:
- Default to LMDE and neutral wording for the incumbent ecosystem; name specific products only when it helps the reader.
- Compare: name the program once, then use neutral phrases for the rest of the section (nominative fair use).
- No implied endorsement or wire-level compatibility unless a normative doc proves it. Use “OneNet-style” / “N2K-class” only for general categories of behavior.
- NMEA 2000® and NMEA OneNet® are NMEA marks—spell correctly; ® on first prominent use where counsel advises. Other names above are third-party marks—treat likewise.
- Pelorus is not an NMEA product name and is not “NMEA-compatible” unless a conformance document establishes that with tests.