Introduction #

The Controller Area Network (CAN Bus) is a communication protocol widely used in automotive, industrial, and embedded systems. It was originally developed by Bosch in the 1980s to enable reliable, real-time communication between electronic control units (ECUs) in vehicles without the need for a complex wiring harness.

At its core, CAN Bus is a robust, message-based network that allows multiple devices (called nodes) to exchange data efficiently over just two wires (CAN High and CAN Low). Instead of each device needing direct connections to every other device, all nodes share the same bus and decide who “speaks” when using a priority-based arbitration system.

Some key characteristics of CAN Bus include:

• Reliability – Built-in error detection and fault confinement make it suitable for safety-critical applications.
• Efficiency – Uses a compact binary message format, enabling fast and real-time communication.
• Scalability – Supports many nodes on a single network, making it flexible for complex systems.
• Robustness – Differential signaling over twisted pair wires reduces noise interference, ensuring stable performance even in harsh environments.

Because of these qualities, CAN Bus has become a standard communication backbone in modern vehicles, and it is increasingly used in industrial automation, robotics, medical equipment, and other fields where dependable, real-time data exchange is required.

Protocols #

While the CAN Bus defines how data is transmitted on the network, many higher-level protocols specify how that data is structured and interpreted. These protocols define message formats, addressing schemes, and diagnostic services, allowing different devices and manufacturers to communicate in a standardized way.

Two protocols relevant for V-Link are:

Volvo Extended Frame (VECU / proprietary CAN) #

Volvo uses an extended CAN frame format (29-bit identifier) for many of its systems. This allows more unique message identifiers compared to the standard 11-bit format. In Volvo’s implementation:

• Messages often follow manufacturer-specific structures not fully published in open standards.
• Extended frames provide space for more ECUs and functions within the same network.
• Volvo applications may include proprietary diagnostic and control messages, meaning interpretation often requires manufacturer documentation or reverse-engineering.

Unified Diagnostic Services (UDS, ISO 14229) #

UDS is a standardized diagnostic protocol that runs on top of CAN (usually using ISO-TP for message segmentation). It is widely used across the automotive industry, including Volvo, to support diagnostics and programming.
Key features of UDS include:

• Service-oriented communication – messages are structured as requests and responses.
• Diagnostic services – such as reading fault codes (DTCs), monitoring sensor values, and controlling actuators.
• Reprogramming – supports flashing ECU software and parameter updates.
• Standardization – UDS services are defined in ISO 14229, but manufacturers often add custom extensions.

Together, these protocols extend CAN Bus beyond raw message exchange, enabling system diagnostics, software updates, and manufacturer-specific control functions.