Technologies developed for automotive applications frequently transfer to other markets due to automobile manufacturers’ rigorous requirements for reliability, performance, and the need for fast data rates in an electronically hostile environment. That’s why Gigabit Multimedia Serial Link (GMSL) cameras are finding ready markets for vision applications in areas such as automation and robotics, smart agriculture, digital healthcare, avionics, robotaxis, and retail and warehouse inventory management. Initially introduced for addressing applications for high-speed video and data transmission in vehicles, Analog Devices GMSL is a widely adopted and proven technology for bringing new levels of performance to high-speed video links and enabling multi-streaming over a single cable. Vision applications require very large data streams to ensure high- quality video. A full HD image is comprised of 1080 rows by 1920 columns. That amounts to 2 million pixels, each of which consists of a red, green, and blue element, resulting in 6 million elements. Each element represents 8 bits of data, so every frame results in nearly 50 Mbps of data. At 60 frames per second, the required data rate for one camera is over three-and-a-half Gbps.
low-voltage differential signaling (LVDS) standard to deliver parallel data downlink rates up to 3.125 Gbps. That was particularly suited for conveying data from multiple camera systems and other advanced driver assistance applications (ADAS), as well as the growing use of in-car, high- definition flat panel displays. A second generation, GMSL2, was introduced in 2018, increasing data rates up to 6 Gbps and supporting more standard highspeed video interfaces, including HDMI and the MIPI interface standard, a popular image sensor interface for consumer and automotive cameras. These advances accommodated full high definition (FHD) displays and cameras with resolution up to 8 MP. GMSL3, the next generation, can deliver data up to 12 Gbps over a single cable, supports multiple 4K resolution streams, the daisy- chaining of multiple displays, and aggregation of multiple cameras such as those located on the front, back, and sides of a vehicle to provide a 360° viewing capability. Today, increasing numbers of automobile manufacturers supplement rear and side-view mirrors with cameras, utilize forward and rear-facing cameras for collision avoidance, and internal cabin cameras for monitoring driver and passenger safety. GMSL3 can aggregate data from multiple video feeds as well as LiDAR and radar.
With cameras scaled down to the level of CMOS sensors, they can produce what once was considered incredible quality at low cost and with low power demands. Image sensors have millions of receptor elements, each of which converts measurements into digital values to be streamed via serial data lanes of a parallel interface, along with synchronization information. Both GMSL2 and GMSL3 utilize MIPI interface standards that provide designers and vendors access to a wide range of image sensors for GMSL cameras. GMSL versus GigE Engineers starting out on vision applications will no doubt quickly face a decision on whether to use GMSL or gigabit Ethernet (GigE) vision technology. GigE is widely used in industrial applications due largely to its reliance on Ethernet network infrastructure and standards. GigE Vision cameras with 2.5 GigE, 5 GigE, and 10 GigE are commonplace in applications today, and 100 GigE state-of-the- art cameras can utilize up to a 100 Gbps data rate. GMSL is designed to transmit data over coaxial cable or shielded twisted pair cable at up to 15 meters, compared to 100 m for GigE, although both may be exceeded under certain conditions. Each technology is capable of transmitting data and power
Road-tested GMSL cameras drive into new markets
Written by Pete Bartolik
First-generation GMSL, first available in 2008, utilized the
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