The automotive industry is moving fast, and the ability for vehicle systems to communicate with each other is more important than ever. As an automotive engineer, it is crucial to understand the top five automotive protocols to help ensure vehicles operate safely, reliably, and efficiently.

• Automotive communication protocols allow data to flow between Electronic Control Units (ECUs).
• For many years, the Controller Area Network (CAN) protocol has been the foundation of most automotive networks.
• There are protocols even more specialized than CAN. These other protocols like LIN, FlexRay, MOST, and Automotive Ethernet serve functions with different objectives, from simple controls to high-speed multimedia communications.
• Understanding these protocols can help engineers design vehicles that are increasingly safer and better connected.

Keeping up to speed with the changes in communications, relay protocols and standards may potentially improve your career and the automotive industry.

1.What Are Automotive Communication Protocols?

Automotive protocols are the rules and standards that allow various vehicle parts – called Electronic Control Units (ECUs) – to communicate effectively. Consider a car to be a tiny networked computer with multiple “brains” controlling the engine, brakes, airbags, infotainment, etc. One task of protocols is to ensure messages are communicated clearly and without errors, essential for performance and safety.

Today’s cars contain dozens, or, in some situations, hundreds of ECUs. Without sound protocols in place the communication these critical components provide could not effectively work together and could ultimately cause failures and safety risks.

Why CAN Is the Most Popular Protocol

Developed by Bosch in the 1980s, the CAN protocol is the primary communication bus within the vast majority of cars today. The protocol allows for the communication of different ECUs to one another in a manner which can be accomplished quickly, reliably and with built-in error correcting features.

The CAN protocol offers communication speeds up to 1 MB, and a multi-master communication model which allows for a number of ECUs to initiate communication, preventing the accidental interrupting of other messages. The CAN protocol provides message priorities, meaning critical information (e.g., a brake message) would never be delayed.

The use of the CAN protocol typically includes engine controls, ABS, and airbags, as well as versions of the protocol including Standard CAN and CAN-FD (Flexible Data Rate) which increase bandwidth or throughput capabilities for modern applications.

2. Local Interconnect Network (LIN) Protocol

Where LIN Shines: Simple and Cost-Effective

Although CAN is fast and powerful, not all car systems ought to be fast. There are systems that are slower and do not deal with critical parts of the car, where the LIN protocol can be used instead. LIN, or Local Interconnect Network employs a single wire connection and uses a master-slave relationship with one master and many slaves. LIN is limited to a communication speed of up to 20 kbps making it ideal for applications like door locks, window winders, and interior lighting. Because LIN is cheaper and simpler, it allows manufacturers to cut costs on low-cost, low-demand, body-related subsystems that do not require safety margins.

High Speed and Safety for Advanced Systems
For safety-critical applications that demand very precise timing, such as steer-by-wire and brake-by-wire systems, FlexRay is the primary protocol of choice.

FlexRay supports a communications speed of up to 10 Mbps and employs both time-triggered and event-triggered communication methods. FlexRay incorporates redundant channels for greater fault tolerance (if one path fails, then communication still occurs).

FlexRay is perfectly suited for advanced driver assistance systems (ADAS) and autonomous driving technology.

4. Media Oriented Systems Transport (MOST) Protocol

The Multimedia Network Inside Your Car
Today’s vehicles are equipped with entertainment systems, ranging from high-quality music players to video streaming screens. The MOST protocol is designed to handle multimedia data in a more efficient way.

MOST employs a ring topology and synchronizes audio and video to allow for seamless playback without buffering or delays. MOST is also used for head units, navigation systems, and rear seat entertainment.

Most importantly, MOST is not designed to handle safety critical control, and principally supports seamless multimedia playback.

5. Automotive Ethernet

The Future Network for Connected and Autonomous Vehicles
As vehicles get more connected and autonomous, data requirements are increasing dramatically. Automotive Ethernet provides the bandwidth needed to support systems such as ADAS, infotainment, and vehicle-to-everything (V2X) communication.

Automotive Ethernet supports speeds from 100 Mbps up to 10 Gbps. With an IP based communication framework, it has a lot of built in IP networking standards and it is scalable to future technologies.

It will also enable simple integration to external networks which will provide cloud-connected vehicle diagnostic capabilities and the potential for over-the-air/software updates.

Conclusion

Knowledge of the major automotive protocols including CAN, LIN, FlexRay, MOST and Automotive Ethernet are critical for any automotive engineer. The speed of advancement in vehicle technology necessitates corporate training in the best and most efficient manner available in order for engineers to learn and hone their skills or at least leverage the most up to date standards for communications. Further, investing in corporate training ensures that teams are prepared to innovate where they can, and make safer and smarter vehicles.