With the popularization of automotive cameras and large screens, how to lead the upgrade of video technology with innovative bus connections...

With the acceleration of automobile electrification and the continuous upgrading of autonomous driving function levels, there are more and more electronic components in automobiles. The efficient information exchange of so many electronic units faces increasing challenges. For example, the enhancement of autonomous driving functions requires more automotive sensors, and traditional point-to-point communication can no longer meet the needs, so advanced bus technology must be adopted. In particular, with the popularization of cameras in autonomous driving and high-definition large screens becoming standard in automobiles, the demand for stable and reliable high-definition video connections has surged.

Traditional automotive buses realize the communication network for interconnecting the underlying automotive devices or automotive instruments in the vehicle network. The four types of automotive buses, mainly CAN bus, LIN bus, FlexRay bus and MOST bus, dominate the mainstream. However, these automotive buses, which have been on the market for more than ten years, have more or less some shortcomings in the face of the new features of current automotive video applications. Among them, the communication connection of the camera is one of the application challenges. Automotive cameras are one of the key sensors driving the development of self-driving cars. As new applications continue to emerge, the number of automotive cameras is also increasing rapidly. In addition, as the application of cameras shifts from high-end cars with low ownership to the larger mainstream automotive market, the adoption rate of cameras continues to rise.

The demand for high-quality automotive video is increasing dramatically, and C2B provides a new option for efficient connection

As the number of cameras increases, the need for higher resolution also emerges. Automakers need to ensure that new cars are equipped with the latest display technology when they are launched so that their display systems are not outdated for as long as possible. Automakers are constantly increasing the size and resolution of in-vehicle displays. To display camera images on these larger and higher-resolution displays, higher-resolution cameras are required. Using existing standard-definition cameras will result in a very poor user experience. In order to provide a better customer experience, high-definition cameras are required. Adding these cameras requires additional costs - not only the cost of increasing the number of sensors and image processing, but also the cost of transmitting video data from the camera to the processing unit through the vehicle wiring harness.

The need for more cables in the car camera link may seem insignificant, but considering that the vehicle wiring harness is the third most expensive component in the car after the engine and chassis, and its weight is also the third in the car, the choice of cables and connectors is critical. As these harnesses are added to the vehicle, the car production line becomes more and more problematic, and any additional production steps will further increase costs. And as electric vehicles become more popular, the additional weight of the harness will directly affect the vehicle's mileage.

To address this, Analog Devices has developed a new automotive camera link technology, the Car Camera and Video Bus (C2B™), which is the only technology optimized for automotive camera links and can solve these problems. C2B covers three main solution-defining standards:

Reuses existing SD unshielded twisted pair cables and connectors to provide the simplest HD camera link upgrade.

Use this link to transmit high-definition video with excellent picture quality.

Use this link to meet automotive-grade EMI/EMC requirements.

Multi-dimensional performance review: C2B bus meets the most demanding automotive applications

The C2B car camera bus is a dedicated automotive video link that provides high-definition video access through existing low-cost standard NTSC cables, supporting the transmission of HD resolution video through existing SD UTP cables and connector links. C2B can easily upgrade from SD cameras to HD cameras without changing existing cables and connector links, making it an important, cost-effective and versatile solution for OEMs.

Another advantage of reusing unshielded twisted pair is that it can use the unused pins of the existing plug-in connector on the host and camera electronic control units (ECUs). This avoids the use of dedicated separate connectors required for SERDES technology, does not take up limited and valuable PCB space in the host and camera ECU modules, and does not increase the cost of the system solution.

C2B transmission was chosen to provide the highest robustness for this automotive application. The signaling scheme can reduce cable bandwidth requirements by 10 times compared to other solutions. Existing links have been proven in actual field applications, so there is no need to evaluate and identify new links, greatly simplifying the upgrade of HD cameras. In addition, because C2B technology uses an optimized transmission scheme and supports longer cable lengths (up to 30 meters), it allows OEMs to freely determine their link design and avoid some of the limitations brought by other technologies.

C2B technology can support high-resolution cameras through low-cost cables and connectors, but since the link has no shielding function, does not provide anti-interference protection, and cannot directly attenuate radiation, how can this C2B bus video transmission meet EMI/EMC performance considerations? ADI's solution is to ensure low radiation and high anti-interference performance to meet strict automotive EMI/EMC requirements, and the design of the transceiver is crucial. From the beginning, the definition and design of C2B was intended to meet this requirement of the automotive industry, and it has proven to be robust and able to meet automotive EMI/EMC requirements.

In addition, C2B supports many other features, including sideband control communication over the same unshielded twisted pair, which supports remote configuration of camera modules, further simplifying camera design. C2B also provides freeze frame detection, which is a key feature for many OEMs.

These transceiver solutions are key to achieving high-performance automotive video connectivity buses

CB provides an optimized solution to enable easy upgrade from NTSC to HD cameras using existing video links while providing excellent video quality and robust EMI/EMC performance. This exciting new technology offers many advantages and provides an optimal system solution to the growing complexity of connecting multiple cameras in the car. CB has proven to be a very cost-effective solution, for example, Denso has worked with ADI to use its CB technology to implement scalable camera and video connectivity solutions in its vehicle product line.

Among the C2B product solutions currently being applied, the transmitter ADV7990/91 and the receiver ADV7380/81, which have been put into mass production, are the main product combinations. This group of transceiver products has the advantages of negligible latency and support for uncompressed transmission. The bidirectional control channel uses the same cable, so there is no additional cost. These devices support 75 MHz pixel rate (75 MHz Y, 75 MHz C) "freeze frame" detection, while the bidirectional control function supports I2C, interrupt/status and general-purpose I/O (GPIO). The innovative cable compensation design has excellent performance, supports 30-meter cables with multiple online connections, and resolutions up to 2 million pixels (at 30 Hz) or 1 million (at 60 Hz).