High-speed data transmission is a critical component of modern sensor fusion applications. Gigabit Multimedia Serial Link (GMSL) plays a key role in this context. This video interface allows efficient transmission of high-resolution sensor data, enabling multi-stream applications. Another key advantage of GMSL is its reliability and robustness. Common applications include advanced driver assistance systems (ADAS) and camera monitoring systems (CMS/CCTV).
GMSL was originally developed by Maxim Integrated of California. That company no longer exists, having been acquired by Analog Devices in 2021. However, GMSL has continued its global success story in the automotive industry and is now valued in a wide range of sectors, including automated guided vehicles (AGVs), collaborative robots (cobots), autonomous mobile robots (AMRs), agriculture and off-highway applications.
The success of GMSL technology is based on its superior characteristics in terms of data rate, latency, low power consumption, full-duplex communication and high data integrity.
GMSL3 supports data rates up to 12 Gbps and GMSL2 up to 6 Gbps, both with very low latency. This enables the transmission of high-resolution sensor data in real-time applications. As such, GMSL is often used in sensor fusion scenarios where data from multiple high-resolution cameras and other sensors such as radar or lidar need to be transmitted, consolidated and processed by the same processor in real time.
GMSL significantly reduces cabling complexity by carrying both power and video signals over the same coaxial cable (PoC) - meaning only a single cable is required. Sensors such as cameras connected via GMSL can be powered directly from this interface without the need for an additional power cable. With GMSL2 and GMSL3 in particular, it is possible to transmit not only video and power, but also control commands, synchronisation signals, haptic and touch data, software updates, status messages and more - all over a single connection. GMSL also supports the simultaneous transmission of sensor, power and control data using serial protocols such as SPI (Serial Peripheral Interface) or I²C (Inter-Integrated Circuit) in both directions (duplex communication). By optimising the use of bandwidth, GMSL achieves extremely low latency and supports high resolution cameras due to its high data rates. This reduces costs, improves reliability and increases the overall life of the application, as cables and connectors are among the most common sources of failure.
GMSL technology enables long-distance transmission over lengths of up to 15 meters. Cameras can be positioned as far as 15 meters away from the host processor without compromising transmission speed, high frame rates, or low latency.
Because high-resolution video data contains a large amount of information, it is compressed before transmission. The serialiser (SerDes) processes the incoming parallel data from the sensor and converts it into a sequential serial data stream. This data is sent in packets. At the other end of the cable, the deserialiser (Des) receives the serial data packets and converts them back to their original parallel form so that the embedded computer can interpret them correctly. The video data is then processed for applications such as driver assistance systems, precision agriculture, environmental monitoring or autonomous driving.
For all its advantages, GMSL has its drawbacks. One of the main challenges is the more complex system integration compared to camera interfaces such as USB or TCP/IP. In particular, the use of the Virtual Channel framework presents technical hurdles for developers. These challenges affect both hardware configuration and software integration, and require a deep understanding of the underlying technologies.
It is particularly important that the serialiser and deserialiser are compatible, i.e. they must be from the same product family. In addition, the deserialiser must be compatible with the processor that processes the data. Only if the processor supports the output format (e.g. MIPI-CSI) can the data be further processed. The following sections describe these challenges in more detail.
Since multiple sensors and serialisers often share the same physical I²C address, it is necessary to assign unique proxy addresses. These are set at runtime by the deserialiser to avoid address conflicts and to ensure clear and unambiguous communication.
Virtual channels are used to transmit multiple video streams in parallel over a shared CSI interface. Each stream is assigned a unique virtual channel ID, which must be correctly configured on both the sensor and receiver side to ensure accurate and error-free data mapping.
The correct setup of the device tree is critical to the overall functionality of the system. This includes defining CSI lanes, bandwidth parameters, power supplies and the exact mapping of components to each other. If configured incorrectly, camera streams will typically not be received and troubleshooting can be extremely time consuming.
The simultaneous use of multiple sensors requires precise synchronisation, especially if they communicate via the same CSI port. Different lane configurations or asynchronous operating modes can lead to data loss or misinterpretation. Potential problems include image flicker during scene changes and suboptimal image quality due to poor sensor calibration. In addition, support for certain hardware configurations, such as 4x CSI aggregators, has not been fully validated by all manufacturers.
GMSL was originally developed for the automotive industry. As a result, GMSL camera manufacturers have optimised their production for high volumes (typically >1000 units). This presents a sourcing challenge for companies that only need small quantities.
As a provider of AI-enabled embedded computers, Syslogic offers a range of devices based on NVIDIA Jetson modules with GMSL interfaces. These embedded computers are ideal for processing video data. To simplify camera integration for end users, Syslogic has partnered with camera manufacturers. GMSL cameras from manufacturers such as Stereolabs, e-con Systems, D3 Embedded and Valeo are pre-configured for compatibility with Syslogic hardware. This reduces time to market and simplifies system integration.
