Service Interface Definition (ARXML) - AUTOSAR Adaptive Platform

ServiceInterface ARXML Elements

XMLTemperatureService.arxml

<AUTOSAR>
  <AR-PACKAGES>
    <AR-PACKAGE>
      <SHORT-NAME>SensorApp</SHORT-NAME>
      <ELEMENTS>
        <SERVICE-INTERFACE>
          <SHORT-NAME>TemperatureServiceInterface</SHORT-NAME>
          <SERVICE-INTERFACE-VERSION>
            <MAJOR-VERSION>1</MAJOR-VERSION>
            <MINOR-VERSION>0</MINOR-VERSION>
          </SERVICE-INTERFACE-VERSION>
          <EVENTS>
            <VARIABLE-DATA-PROTOTYPE>
              <SHORT-NAME>Temperature</SHORT-NAME>
              <TYPE-TREF>/Types/float32</TYPE-TREF>
              <!-- isReliable=false → UDP; true → TCP -->
            </VARIABLE-DATA-PROTOTYPE>
          </EVENTS>
          <METHODS>
            <CLIENT-SERVER-OPERATION>
              <SHORT-NAME>Calibrate</SHORT-NAME>
              <ARGUMENTS>
                <ARGUMENT-DATA-PROTOTYPE>
                  <SHORT-NAME>offset</SHORT-NAME>
                  <TYPE-TREF>/Types/float32</TYPE-TREF>
                  <DIRECTION>IN</DIRECTION>
                </ARGUMENT-DATA-PROTOTYPE>
              </ARGUMENTS>
            </CLIENT-SERVER-OPERATION>
          </METHODS>
          <FIELDS>
            <FIELD>
              <SHORT-NAME>Status</SHORT-NAME>
              <TYPE-TREF>/Types/SensorStatus</TYPE-TREF>
              <HAS-GETTER>true</HAS-GETTER>
              <HAS-SETTER>false</HAS-SETTER>
              <HAS-NOTIFIER>true</HAS-NOTIFIER>
            </FIELD>
          </FIELDS>
        </SERVICE-INTERFACE>
      </ELEMENTS>
    </AR-PACKAGE>
  </AR-PACKAGES>
</AUTOSAR>

Data Type Mapping

AUTOSAR Type	C++ Type	Notes
uint8	`std::uint8_t`
float32	`float`	IEEE 754 single-precision
Array	`ara::core::Array<T,N>`	Fixed-size, stack-allocated
Vector	`ara::core::Vector<T>`	Dynamic, heap-allocated — avoid in ASIL context
Optional	`ara::core::Optional<T>`	Like std::optional
String	`ara::core::String`	UTF-8, avoid in hard real-time paths

Version Management

ServiceInterface versioning uses Major.Minor. Compatibility rule: same Major version is required; a proxy with Minor 1 can talk to a skeleton with Minor 2 (skeleton is backwards-compatible). A Major version mismatch causes CM to reject the connection with error kVersionMismatch.

⚠️ Breaking Changes

Removing or reordering fields/events/methods is a Major version change. Adding new optional events is a Minor change. Changing a data type is always a Major change. Follow semantic versioning strictly — silent incompatibilities are extremely hard to debug at vehicle level.

ARXML Toolchain

Tool	Vendor	Function
DaVinci Developer	Vector	ARXML authoring + arxml2cpp code gen
ISOLAR-EVE	EB (Elektrobit)	ARXML authoring, validation, EB corbos gen
SystemDesk	dSPACE	System architecture + Adaptive integration
APEX.AI Apex.OS	APEX.AI	Open-source-derived, ROS2-compatible bindings

💡 arxml2cpp Output

arxml2cpp generates four files per ServiceInterface: <Name>Skeleton.h, <Name>Proxy.h, and corresponding .cpp stubs. The generated types in common/<Name>Common.h define the C++ data structures used in Send() and GetNewSamples().

Summary

The ARXML ServiceInterface is the single source of truth for Events, Methods, and Fields. It drives code generation, version compatibility checking, and manifest validation. Invest time in a clean interface definition before writing any application code — changing it later forces regeneration and API updates in all consumers.

🔬 Deep Dive — Core Concepts Expanded

This section builds on the foundational concepts covered above with additional technical depth, edge cases, and configuration nuances that separate competent engineers from experts. When working on production ECU projects, the details covered here are the ones most commonly responsible for integration delays and late-phase defects.

Key principles to reinforce:

Configuration over coding: In AUTOSAR and automotive middleware environments, correctness is largely determined by ARXML configuration, not application code. A correctly implemented algorithm can produce wrong results due to a single misconfigured parameter.
Traceability as a first-class concern: Every configuration decision should be traceable to a requirement, safety goal, or architecture decision. Undocumented configuration choices are a common source of regression defects when ECUs are updated.
Cross-module dependencies: In tightly integrated automotive software stacks, changing one module's configuration often requires corresponding updates in dependent modules. Always perform a dependency impact analysis before submitting configuration changes.

🏭 How This Topic Appears in Production Projects

Project integration phase: The concepts covered in this lesson are most commonly encountered during ECU integration testing — when multiple software components from different teams are combined for the first time. Issues that were invisible in unit tests frequently surface at this stage.
Supplier/OEM interface: This is a topic that frequently appears in technical discussions between Tier-1 ECU suppliers and OEM system integrators. Engineers who can speak fluently about these details earn credibility and are often brought into critical design review meetings.
Automotive tool ecosystem: Vector CANoe/CANalyzer, dSPACE tools, and ETAS INCA are the standard tools used to validate and measure the correct behaviour of the systems described in this lesson. Familiarity with these tools alongside the conceptual knowledge dramatically accelerates debugging in real projects.

⚠️ Common Mistakes and How to Avoid Them

Assuming default configuration is correct: Automotive software tools ship with default configurations that are designed to compile and link, not to meet project-specific requirements. Every configuration parameter needs to be consciously set. 'It compiled' is not the same as 'it is correctly configured'.
Skipping documentation of configuration rationale: In a 3-year ECU project with team turnover, undocumented configuration choices become tribal knowledge that disappears when engineers leave. Document why a parameter is set to a specific value, not just what it is set to.
Testing only the happy path: Automotive ECUs must behave correctly under fault conditions, voltage variations, and communication errors. Always test the error handling paths as rigorously as the nominal operation. Many production escapes originate in untested error branches.
Version mismatches between teams: In a multi-team project, the BSW team, SWC team, and system integration team may use different versions of the same ARXML file. Version management of all ARXML files in a shared repository is mandatory, not optional.

📊 Industry Note

Engineers who master both the theoretical concepts and the practical toolchain skills covered in this course are among the most sought-after professionals in the automotive software industry. The combination of AUTOSAR standards knowledge, safety engineering understanding, and hands-on configuration experience commands premium salaries at OEMs and Tier-1 suppliers globally.