Overview
ISO 17356-4:2005 - "Road vehicles: Open interface for embedded automotive applications - Part 4: OSEK/VDX Communication (COM)" defines a uniform, message‑based communication environment for automotive ECU application software. The standard increases portability, reusability and interoperability by specifying a common Interaction Layer (IL) API and behavior for both internal (intra‑ECU) and external (inter‑ECU) communication, independent of specific bus protocols or network technologies.
Key topics and requirements
- Message-based model: Communication is organized around messages (signals) that carry application data. Messages are configured statically via OIL (ISO 17356-6).
- Interaction Layer (IL): Provides the COM API with services for initialization, data transfer and communication management. IL hides protocol/bus differences to improve portability.
- I‑PDUs and message packing: One or more messages are packed into Interaction Layer Protocol Data Units (I‑PDUs). Messages occupy contiguous, bit‑aligned regions within I‑PDUs and are sized in bits.
- Internal vs external communication: Internal communication delivers message data immediately within an ECU; external communication updates I‑PDUs and uses lower layers to transmit across the network.
- Message objects and identifiers: Sending and receiving message objects are configured at system generation and identified by message IDs. Supports m:n communication patterns.
- Queued vs unqueued receiving: Receiving message objects can be queued (FIFO, read removes the oldest message) or unqueued (last value readable multiple times). Queue sizes are defined per object.
- Transfer properties & transmission modes:
- Triggered vs Pending transfer properties for external messages.
- I‑PDU transmission modes: Direct, Periodic, and Mixed.
- Byte order conversion (endianess): IL performs network-to-local CPU conversion per message to ensure interoperability across heterogeneous ECUs.
- Non‑blocking send services & notifications: Transmit services are non‑blocking; the API includes notification mechanisms and deadline monitoring for transfer/reception status.
- Scalability & conformance classes: Multiple conformance classes allow implementations to scale to different hardware resource constraints.
- Lower-layer requirements: Clause 4 defines minimum requirements for Network and Data Link Layers to support IL features.
- Annexes: Guidance for using COM with non‑conforming OSes (Annex A), application notes (Annex B), and callout examples (Annex C).
Applications and who uses it
- Automotive software architects and embedded systems engineers designing ECU communication stacks.
- ECU and gateway suppliers implementing portable application modules across platforms.
- Tool vendors producing OIL/system-generation and COM configuration tools.
- Integration teams that require consistent internal/external message semantics across networks and ECUs.
ISO 17356-4 is especially valuable where portability, interoperability and protocol‑independence are priorities (e.g., multi-supplier vehicle platforms, reuse of application software across models).
Related standards
Keywords: ISO 17356-4, OSEK/VDX Communication, COM, automotive ECU communication, Interaction Layer, I-PDU, message-based API, embedded automotive applications, OIL, endianness, conformance classes.
Open preview (PDF)Road vehicles — Open interface for embedded automotive applications — Part 4: OSEK/VDX Communication (COM)
