In the fast-evolving landscape of automotive electronics, the ability to diagnose, monitor, and maintain complex vehicle systems has become a critical requirement. Vehicle diagnostics not only ensures regulatory compliance and safety but also plays a key role in enabling predictive maintenance, reducing downtime, and enhancing customer satisfaction. At the heart of modern automotive diagnostics lies the Unified Diagnostic Services (UDS) protocol, which is most commonly implemented over the Controller Area Network (CAN) — a configuration often referred to as UDS over DoCAN.
We recognize the increasing complexity in embedded automotive systems and the growing need for robust diagnostic capabilities. Our in-house automotive software suite, RAPIDSEA, provides comprehensive support for UDS over DoCAN and accelerates the development of standards-compliant diagnostic features in embedded products. In this article, we explore the importance of vehicle diagnostics, introduce UDS and DoCAN, and show how RAPIDSEA Suite simplifies and speeds up the implementation of these essential features.
The Growing Importance and Challenges of Vehicle Diagnostics
Today’s vehicles are no longer just mechanical systems; they are software-driven platforms with dozens of ECUs (Electronic Control Units) communicating over automotive networks such as CAN, LIN, FlexRay, and Ethernet. With stringent emission regulations, functional safety requirements (ISO 26262), and the increasing demand for over-the-air (OTA) updates, diagnostics is no longer a luxury—it's a necessity.
However, implementing vehicle diagnostics is far from trivial. Developers face several challenges:
Protocol Complexity: Automotive diagnostics protocols like UDS have dozens of services and sub-functions, each with specific timing, security, and session requirements.
Resource Constraints: ECUs often have limited processing power and memory, requiring highly optimized code.
Reliability and Safety: Faulty diagnostics can lead to incorrect troubleshooting or system failures.
Tool Compatibility: Diagnostics solutions must seamlessly integrate with OEM tools like Vector CANoe, ETAS INCA, or Softing DTS.
Regulatory Compliance: Adherence to standards such as ISO 14229 (UDS) and ISO 15765 (DoCAN) is mandatory.
Understanding UDS: The Backbone of Vehicle Diagnostics
Unified Diagnostic Services (UDS) is a communication protocol defined in ISO 14229, designed specifically for diagnostic communication between external test equipment and vehicle ECUs. UDS defines a wide range of diagnostic services categorized by service IDs (SIDs), which can be broadly grouped into:
- Session Management (e.g., 0x10 - Diagnostic Session Control)
- Data Transfer (e.g., 0x22 - Read Data by Identifier, 0x2E - Write Data by Identifier)
- Control Services (e.g., 0x31 - Routine Control, 0x2F - Input/Output Control)
- Security Services (e.g., 0x27 - Security Access)
- Error Management (e.g., 0x19 - Read DTC Information)
UDS operates on a client-server model, where an external diagnostic tester (client) sends requests, and the in-vehicle ECU (server) processes and responds accordingly. These services form the foundation of vehicle maintenance, repair, and ECU flashing.
DoCAN: The Transport Layer Behind UDS
While UDS defines what messages should be exchanged, it does not dictate how they are transmitted. That role falls to the Diagnostic Communication over Controller Area Network (DoCAN) protocol, defined under ISO 15765. DoCAN provides the transport layer for UDS in CAN-based networks.
CAN frames are limited to 8 bytes of payload, but UDS messages can span several hundred bytes. DoCAN addresses this through segmentation and reassembly, using multi-frame transport protocols with First Frame (FF), Consecutive Frame (CF), and Flow Control (FC) mechanisms. Timing constraints such as STmin (minimum separation time) and block size (BS) must be carefully handled to ensure reliable communication.
Together, UDS over DoCAN forms the backbone of vehicle diagnostics in most production vehicles today, and correct implementation is crucial for ensuring tool compatibility and functional reliability.
RAPIDSEA Suite: Powering UDS over DoCAN in Embedded Development
To support embedded developers in rapidly integrating standards-compliant diagnostics into their ECUs, we have built RAPIDSEA — a robust, production-grade automotive software suite. RAPIDSEA offers a modular and highly configurable implementation of UDS over DoCAN, supporting all major UDS services and DoCAN transport mechanisms.
Key Features of RAPIDSEA's Diagnostic Stack:
Full UDS Support: Implements all mandatory and optional UDS services per ISO 14229.
Transport Layer Conformance: Complete DoCAN stack with ISO 15765-2 compliance.
Security Access: Customizable security algorithms and seed-key generation.
DTC Management: Built-in support for Diagnostic Trouble Codes (DTC) handling.
Session and Timing Management: Supports default, extended, programming sessions with flexible P2/P2* timers.
Integration Ready: Seamless integration with popular RTOS and hardware abstraction layers (MCAL).
Tool Compatibility: Validated with leading diagnostic tools like CANoe, INCA, and ODIS.
By using RAPIDSEA, developers can save months of development time and ensure that their diagnostic stack is robust, maintainable, and OEM-compliant.
Beyond Diagnostics: Enabling Intelligent Vehicle Functions
While diagnostics is a major focus, RAPIDSEA is not limited to UDS over DoCAN. The suite supports a wide range of automotive communication stacks, including:
ISO-TP over CAN and CAN FD
LIN protocol stack
UDS over IP (DoIP)
Flash Bootloaders
Diagnostic Event Manager (DEM)
OSEK/VDX compliant OS and RTE layers
For embedded developers, this means the ability to scale from basic ECUs to domain controllers without having to reinvent the wheel. Whether you're building a simple body control module or a high-end ADAS controller, RAPIDSEA provides the building blocks for a robust and scalable software architecture.
Designed for Developers: Easy Customization and Documentation
We understand that each OEM has different requirements—from custom diagnostic identifiers to proprietary security schemes. RAPIDSEA has been architected with extensibility and configurability in mind, allowing developers to tailor the stack to their specific needs.
To make adoption as smooth as possible, we provide:
- Extensive documentation and user guides
- Reference implementations and integration examples
- Dedicated support for integration and validation
- Compliance reports and conformance testing tools
You can explore the detailed documentation of RAPIDSEA's UDS over DoCAN implementation here: RAPIDSEA Documentation.
Conclusion: Accelerate Your Automotive Development with RAPIDSEA
With increasing vehicle complexity, regulatory pressures, and shorter time-to-market, developers cannot afford to spend months building protocol stacks from scratch. Embien’s RAPIDSEA Suite offers a proven, production-ready implementation of UDS over DoCAN, designed for fast integration, high reliability, and complete standards compliance.
Whether you're working on powertrain, infotainment, body electronics, or electrification, RAPIDSEA empowers you to implement advanced vehicle diagnostics, UDS services, and CAN-based communication with confidence.