What can in-vehicle connectivity bring to the industry from analog to digital?

ChatGPT has triggered the demand for digital chips with large computing power that integrate storage and calculation . The existence of ChatGPT relies largely on the support of digital technology. Digital technology is one of the greatest inventions in human history, including coding, compression, transmission, modulation and demodulation. It uses two-digit coding of 0 and 1 to process and transmit information through computers, optical cables , communication satellites and other equipment.

Although the representation method of numbers is very simple, the information they represent can be either discrete, such as numbers, letters, etc., or continuous, such as sounds, images, and measurement results. Today, digital technology has become five major technology systems covering big data, cloud computing , Internet of Things , blockchain, and artificial intelligence.

However, in the so-called most advanced intelligent connected cars, the transmission of on-board data still uses the analog signal transmission method of the fuel vehicle era. Now, that's changing.

Analog vs. Digital Transmission Tradeoffs

Although analog transmission does not need to consider the transmission content, has the advantage of extremely high resolution under ideal conditions, is intuitive and easy to implement, has a simple processing method, and has no quantization error, and can accurately describe physical quantities, its fatal shortcomings are:

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• The signal amplitude changes continuously and is relatively weak, and will attenuate after a certain distance. Therefore, the transmission distance is short, and a power amplifier is required for longer distances;

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• The anti-interference ability is weak, and it is easily interfered by various superimposed noises during the transmission process, and is difficult to eliminate; the signal confidentiality is poor, and the communication is easily eavesdropped.

The advantage of digital transmission is first of all data integrity. The amplitude of the transmitted signal is discrete. There are only two binary signal values. The receiving end only needs to distinguish two states. As long as the size of the noise is not enough to affect the correct judgment, it can receive it correctly. Secondly, it has strong anti-interference ability, which can transmit digital signals to a certain distance before ensuring that attenuation does not endanger the data integrity; in order to reach a longer transmission distance, a transponder can be used. The third is that the bandwidth can be effectively used, and the digitally encoded signal has security and confidentiality.

Therefore, given the advantages of digital transmission, it is generally believed in the communications field that it is better to use digital transmission. In cars, some physical quantities acquired by sensors and cameras , such as speed, temperature, pressure, etc., are analog signals, which need to be converted into digital signals and sent to the computer for processing; and then the processing results are converted into ECU (Electronic Control Unit) Analog signals drive the actuator.

What is the current status of automotive data transmission?

Schematic diagram of wiring architecture in vehicle

Now, the automotive industry is shifting from private protocols to open standards. Some OEMs have realized that data transmission is the bottleneck of in-vehicle communication in intelligent connected cars. They hope to use digital signals and open standards to replace the previously used private protocols.

The so-called private protocols refer to non-open standards customized by some semiconductor manufacturers based on their private technologies. SerDes currently used in automotive applications is this proprietary solution, which means that if not all components come from the same chip supplier, components between manufacturers cannot be used together.

Ser and Des in SerDes represent serializer (Serializer) and deserializer (Deserializer) respectively. Its main function is to convert low-speed parallel signals into high-speed low-voltage differential signals ( LVDS ) and send and receive them through the serial link. Early SerDes technology was applied to long-distance wide area network communications based on optical fiber media . With the continuous improvement of data transmission rates, this technology has expanded to other application fields. Due to SerDes' high-speed transmission characteristics, the automotive field has also used it as an option to achieve high-speed connections in recent years. In September 2020, the MIPI Alliance released the automotive high-speed interconnection standard A-PHY, which is developing rapidly; in 2021, the IEEE Standards Association listed A-PHY as one of its standards, and major well-known OEMs plan to add it to the next Generation solution.

Some members of the MIPI Alliance

In fact, the first chipset that complies with the MIPI A-PHY standard has not been launched for a long time, but more than 30 potential customers and partners are already evaluating it, including Aptiv, LG Innotek, OmniVision Technology ( Omnivision), ON Semiconductor, Mobileye, Intel, Sony, Japan's Sumitomo Electric, Sunny Optical, Keysight Technologies, Leopard Imaging, etc., 8 of which are OEMs and are expected to The first phase integrates the MIPI A-PHY chip into its ADAS platform.

MIPI Alliance members continue to promote the development of the A-PHY ecosystem

A-PHY for cars

So, what is the difference between the MIPI A-PHY standard and traditional SerDes? Will they coexist in automotive applications in the future? Recently, Valens Senior Vice President and Automotive Business Director Gideon Kedem said: “The biggest difference between the two is that MIPI A-PHY is a globally accepted open standard. Chip suppliers can design, develop and produce corresponding MIPI in accordance with this standard. A-PHY chips. "In other words, since there are no patent restrictions, any chip manufacturer with technical capabilities can develop and manufacture chips that meet the MIPI A-PHY standard.

In fact, A-PHY, like the Ethernet standard, helps build a better and more standardized ecosystem in the industry, so many chip players are developing and producing chips that meet the A-PHY protocol. In the future, more and more A-PHY chip manufacturers will appear at home and abroad. However, different chip manufacturers have different R&D capabilities, and the products they produce will have some differences in performance or cost-effectiveness.

At present, in addition to Valens, which was the first to launch a chipset that meets the MIPI A-PHY protocol, manufacturers such as LG Innotek have also joined the ranks of developing and producing MIPI A-PHY chip modules. Collaborators in the MIPI A-PHY camp include Intel (foundry services), Qualcomm (communication chips), NVDIA (artificial intelligence), Japan Star Electronics (connectors), Sony ( image sensors ), and Keysight Technologies (test and measurement) , OmniVision (image sensor), Sunny Optical (vehicle camera), Suzhou Shouzhuan (communication chip), Sades-Benz (vehicle), Mobileye (sensor), etc.

Application scenarios of MIPI A-PHY

So far, there are not many chipsets on the market that comply with the MIPI A-PHY standard, but its advantages in helping to solve many challenges of current electric vehicle development - control complexity, body weight and total connection cost - have attracted attention. effect.

In terms of automotive signal transmission distance, previous protocols such as C-PHY and D-PHY are mainly used for short-distance ECU video transmission, while A-PHY is suitable for longer-distance signal transmission, such as long-distance data transmission from camera to ECU. The distance is up to 15 meters.

The automotive application scenario that is most confusing about transmission distance is large vehicles, and their blind spots have always attracted much attention from the industry and society. Large commercial vehicles (trucks, trucks, etc.) have large visual blind spots, and the risk of traffic accidents is extremely high when reversing. Despite guidelines issued by governments and non-governmental organizations around the world, the safest and most feasible way for truck drivers to back up is to get out of the vehicle and observe.

In terms of policy, in December 2022, my country also released the "Performance and Safety of Motor Vehicle Indirect Vision Devices" standard. One of the highlights is that motor vehicles can cancel traditional optical rearview mirrors and legally install electronic rearview mirrors.

In early 2022, the American heavy truck company Stoneridge trailer was equipped with a VA600R chipset that specifically solves the problem of rear visibility in trucks, enabling the connection between the rear camera and the cabin display. In harsh noise environments, it solves key safety hazards with a high-speed data link up to 40 meters long , improves road safety, and reduces the operating costs of OEMs.

Supports high-speed data links up to 40 meters in harsh noisy environments

Since 2020, the in-vehicle infotainment systems of many mass-produced models of Mercedes-Benz have also been equipped with VA60xx chipsets, including Tier1 supplied to Mercedes-Benz by Harman, Continental, Molex and Bosch. Taking Mercedes-Benz as an example, in the future, several major modules such as automatic transmission control unit (DCU), engine control, and central control electric door lock control may each use one or two such chips.

In addition, the "MIPI A-PHY Technology based on UTP" report by the independent organization A2MAC1 shows that compared with the traditional solution based on GMSL (Gigabit Multimedia Serial Link), the Porsche pure electric sports car Taycan using the MIPI A-PHY surround view system saves The cost is about US$17-27; ordinary passenger cars can save about US$10-20. This is because MIPI A-PHY chips can use lower-cost cable harnesses and connection interface architectures, helping to significantly reduce overall system costs.