Exploring GMSL technology and its role in automotive camera systems

Modern mobility has evolved greatly over the last few decades. Today, a modern vehicle is not just about accelerating and braking -it’s also about safety.

Modern vehicles have become more intelligent and connected. They can adapt to drivers’ needs while significantly enhancing safety. Advanced driver-assistance systems (ADAS) and autonomous driving technologies help achieve these objectives with high-performance camera systems.

At the heart of these systems lies Gigabit Multimedia Serial Link (GMSL) technology from Analog Devices, a robust and scalable solution for high-speed, low-latency video transmission. This blog is all about the fundamentals of GMSL technology, the role it plays in automotive camera systems, and highlights the MAX96724-BAK-EVK evaluation kit as a practical tool for developers available from Farnell.

What is GMSL technology?

GMSL is a high-speed Serializer/Deserializer technology designed to transmit high-bandwidth multimedia data, such as video, audio, and control signals, over a single cable. It supports data rates up to 12 Gbps, making it ideal for real-time, high-resolution video applications. GMSL operates over coaxial or shielded twisted-pair (STP) cables and offers transmission distances of up to 15 meters without compromising signal integrity. This is an important advantage over traditional MIPI CSI-2 interfaces, which are limited to 10–15 cm due to signal degradation.

GMSL technology supports both GMSL1 and GMSL2 protocols. GMSL2, the second generation, offers enhanced features like 4K video support, multi-stream transmission, and bidirectional communication at 3 Gbps or 6 Gbps in the forward direction and 187.5 Mbps in the reverse. Some key features include:

• Low latency: GMSL ensures near-zero-latency transmission, critical for real-time applications like ADAS.
• Power over Coax (PoC): Simplifies cabling by delivering power, data, and control signals over a single coaxial cable.
• Robust EMI/EMC performance: Spread-spectrum technology reduces electromagnetic interference, meeting stringent automotive standards.
• Multi-Camera synchronization: Virtual channel support enables synchronized data from multiple cameras which ensures accurate timestamping for sensor fusion.

These attributes make GMSL a cornerstone for automotive vision systems, where reliability, bandwidth, and flexibility are paramount.

GMSL in automotive camera systems

Automotive camera systems, integral to ADAS and autonomous vehicles, rely on GMSL for high-speed data transfer from multiple sensors to central processing units. Applications include surround-view systems, rearview cameras, and blind-spot monitoring. GMSL’s ability to connect up to four remotely located cameras over long distances (up to 15 meters) allows flexible camera placement in vehicles, overcoming the spatial constraints of MIPI-based systems.

GMSL’s high bandwidth supports high-resolution imagers (up to 8MP), enabling crisp visuals for object detection and lane-keeping algorithms. Its bidirectional control channel provides a real-time communication between cameras and electronic control units (ECUs) that facilitates dynamic adjustments like focus or exposure. Additionally, GMSL’s aggregation and replication capabilities combine video streams from multiple cameras into a single CSI-2 output, streamlining data processing for platforms like NVIDIA Jetson or Ambarella SoCs.

GMSL can tackle critical automotive environments with high Noise, Vibration, and Harshness (NVH), temperature extremes and electromagnetic interferences. GMSL’s compliance with AEC-Q100 Grade 2 and ASIL-B standards ensures functional safety and reliability, making it a preferred choice for automotive OEMs like Tesla, GM and many more.

Figure 1: Transferring power from ECU to the remote camera using GMSL technology

Advantages over competing Technologies

GMSL offers higher data rates (up to 6–12 Gbps) compared to 100 Mbps or 1 Gbps Ethernet used in automotive systems. It offers low latency, and reduced cabling costs when compared to alternatives like FPD-Link III or Ethernet. Its PoC feature simplifies installation, reducing weight and complexity in vehicles. GMSL’s backward compatibility with GMSL1 and scalability to GMSL3 (12 Gbps) ensure longevity and adaptability for future automotive designs.

Evaluate GMSL with MAX96724-BAK-EVKl

For developers looking to harness GMSL technology, the MAX96724-BAK-EVK evaluation kit, available from Farnell, is an excellent starting point. This kit provides a proven platform to evaluate the MAX96724, MAX96724F, and MAX96724R deserializers, which convert four GMSL2/1 inputs to 1, 2, or 4 MIPI D-PHY or C-PHY outputs. The kit is ideal for prototyping automotive camera systems and supports up to 8MP imagers.

The MAX96724-BAK-EVK includes standard FAKRA coaxial or MATE-AX cable interfaces, a Windows 10-compatible GUI for easy configuration, and support for high-bandwidth GMSL2 links (6 Gbps forward, 187.5 Mbps reverse). It enables camera module bring-up, debugging, and video streaming, making it suitable for applications like ADAS, machine vision, and robotics. For a complete evaluation, pair it with a serializer board like the MAX9295A coax EV kit.