【Introduction】Technology is changing the automotive industry, bringing a safer and more comfortable driving experience. Car camera connectivity is a key enabling technology, with an average of four cameras expected in each car by 2024. 1 A major challenge for the industry is how to add additional cameras to vehicles without significantly increasing costs. This article explores the various automotive camera interfaces in terms of cost and performance; and proposes an optimized solution that provides excellent video performance while enabling the use of low-cost wiring harnesses.
The increase in car camera connectivity has been accompanied by a substantial increase in the cost of applications, but enables the car to implement new safety and comfort features. The latest market research estimates that by 2024 there will be an average of four cameras per vehicle as the market responds to consumer demand and follows regulatory requirements. 1 Amid the explosive growth of camera technology, Surround View Monitoring (SVM), Driver Status Monitoring (DSM), and Driving Recording (DVR) are some of the new applications at the forefront of development. SVMs and rear view cameras can help make parking safer. DSM cameras are used to monitor the driver’s position and eye movements to detect and prevent driver distraction. The driving record camera is used to record the accident process. The United Nations’ Automatic Lane Keeping System 2 (ALKS) regulation mandates the use of DSM and driving record cameras, which came into effect in January 2021. Already adopted in more than 60 countries and territories, ALKS is a system that uses Level 3 vehicle autonomy (a self-driving feature that requires the driver to take over if necessary) to keep the car on a predetermined driving route. DSM is also an essential requirement for the Euro NCAP 2020 Assisted Driving Rating System. 3 The automobile manufacturing industry is already one of the industries with the highest debt ratio and the lowest profit in the world. The challenge facing the industry is how to deliver the required camera performance without significantly increasing the cost.
The SVM camera system can provide a 360° surround view of the outside of the vehicle when parked. These systems help reduce the risk of low-speed accidents, especially for pedestrians and visually impaired pedestrians. SVMs will be installed in 70% of vehicles in Asian countries and regions, where congested streets and small parking spaces make parking particularly difficult. SVM is an example of a camera application that illustrates their role in saving lives and creating a great driving experience. SVM can also be an interesting case for performing a performance-cost analysis of automotive camera systems. Each SVM system uses 4 cameras to create panoramic views. HD cameras typically use coaxial cables, which are expensive, bulky, and difficult to deploy into tight spaces. Using coaxial wiring harnesses for SVMs requires the use of expensive coaxial connectors, making car OEMs pay millions of dollars in additional model costs. The automotive industry is facing a big question: which video interface of the camera provides the optimal cost point?
Still using SD solution is not a good option
For many years, most automotive camera designs have used standard definition (SD) cameras. They use low-cost cables and connectors to minimize the system cost of the SVM module. However, SD camera systems typically only provide 100mA of bulk current injection (BCI), while most OEMs today require 200mA BCI performance. As the size of the Display in the cab increases, the video performance of the standard definition camera system is no longer satisfactory. Standard definition video (720 x 480) is very small and needs to be scaled to fit modern car display sizes (eg 1920 x 720). Scaling involves inserting or creating new pixels to fill that space. The insertion process can cause many visual artifacts, including (for example) aliasing on the diagonal. Consumers have grown accustomed to the HD camera performance offered by smartphones and can no longer accept SD performance. While SD video offers an extremely low-cost solution, its limited EMC/I (BCI) and video performance has many OEMs planning to phase out SD cameras on all vehicle models by 2025.
LVDS is expensive to implement
Low-Voltage Digital Signal (LVDS) camera links provide a high-performance yet costly solution for automotive HD cameras. LVDS is a digital serial transmission scheme that accurately transmits video from a camera to an Electronic control unit (ECU). LVDS camera solutions are ideal for high-end front-facing cameras of 4-8 megapixels. Among automotive cameras, front-facing cameras require the highest video resolution to support adaptive cruise control, object detection, traffic sign recognition, and collision avoidance. LVDS uses high bandwidth and requires shielded cables in order to pass automotive EMC and EMI testing. LVDS links typically use coaxial and micro coaxial cables. The bend rate of these cables, as well as their durability through multiple bends, makes their manufacture a problem for automotive OEMs, for example, to deploy cables through door hinges to mount cameras on mirrors, or on the roof of the car for occupant status monitoring, or even behind the front seats for video conferencing. The cost of coaxial connectors makes HD camera connections prohibitively expensive for low-end and mid-range vehicles.
Figure 1. Camera and connectors for in-vehicle C2B
C2B support enables leading technology solutions
An alternative is to use specially designed technology to meet these automotive challenges. Car Camera Bus™ (C2B™) is an automotive high-definition camera link technology with performance comparable to an LVDS interface. C2B can deliver HD performance over a low-cost UTP harness that avoids costly coaxial connectors. C2B can reuse the plug-in connector in the wiring harness to achieve extremely low wiring harness cost. In addition, automotive OEMs will use the C2B video interface with existing UTP wiring harnesses to reduce the cost of upgrading from SD cameras to HD cameras. The C2B provides optimized video encoding, differential mode signaling, and internal filtering to achieve exceptionally robust EMC performance with a UTP infrastructure, including compliance with 200mA BCI testing requirements. The C2B camera can be remotely controlled from the ECU through a high-speed reverse channel on the same twisted pair. Backchannel allows manufacturers to optimize camera performance based on lighting conditions, which is significantly better than NTSC cameras. The lower system cost of C2B enables automotive OEMs to implement HD camera resolutions in low-end and mid-range models.
Table 1. Technology Comparison
C2B is an excellent solution for the automotive industry, delivering outstanding HD camera performance at a sustainable and reasonable system cost for mass market needs. C2B enables all vehicles to be equipped with camera systems, enabling the deployment of safety-critical systems for the benefit of all traffic participants. For more information on C2B technology, visit analog.com/C2B, analog.com/ADV7992, analog.com/ADV7382, or analog.com/ADV7383.
1 “Detection and Computing for ADAS Vehicles of the Year 2020.” Yole Développement, 2020.
2 “United Nations “Automatic Lane Keeping System” Regulations
It is a major milestone in the safe introduction of autonomous vehicles. “UNECE, June 2020.
3 “Assisted Driving Testing 2020: What’s New in 2020?” Euro NCAP, 2020.
4 Andrew Edgecliffe-Johnson, Peggy Hollinger, Joe Rennison, Robert Smith. “Will Covid-19 trigger a corporate debt crisis?” Financial Times, March 2020.
Pandey, Anchal. “U.S. NTSB recommends driver monitoring systems.” PathPartner, July 2020.
About the Author
Paul Slattery, Strategic Marketing Manager for the Automotive Connectivity and Sensing Products Group at Analog Devices, joined the Marketing team in 2016 and before that worked in the Applications and Product Engineering teams. Paul understands automotive connectivity solutions well and has helped define the C2B product line. He holds a Bachelor of Engineering and a Master of Business Administration from the University of Limerick, Ireland. Contact: email@example.com.
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