Research on the information performance advantages of Suruide in-vehicle Ethernet hardware and applications
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The development of vehicle communication technology has evolved from serial communication to industrial bus and then to bus network. With the increase of vehicle electronic control and information devices and the increasing demand for information services, the application of more advanced computer networks in vehicles is inevitable, especially the application of multimedia information, electronic maps, Internet information, etc. in vehicles. Buses such as CAN can only meet some functions, but it is difficult to meet the bandwidth and transmission form. From now on, vehicle Ethernet has been implemented in various luxury car series.
As Ethernet technology matures and is widely used, people naturally think of using it in cars to meet this demand. However, the current costs of software and hardware are relatively high. Because the in-vehicle environment and the requirements for in-vehicle network data transmission are very different from the original design of Ethernet, if Ethernet is used in a car, it must be appropriately modified to maintain the advantages and characteristics of Ethernet while meeting the requirements of the vehicle environment. This is the so-called in-vehicle Ethernet.
Figure 1: Suruide cracked Tesla Ethernet data
Based on the different data types and transmission frameworks of network communications in cars, Su Rui De collects data from in-vehicle Ethernet information communications. Taking Tesla as an example, Su Rui De already has Tesla Model 3 network topology and vehicle circuit diagrams. It obtains left ( L ) and right ( R ) body controller unit BCM , motor controller unit, and front body controller data through LIN , CAN , CAN-FD , and Ethernet . It is used for vehicle control strategy data research, data acquisition and collection development, and teaching. The in-vehicle network has 3 -way CAN and 4- way LIN , which are not as good as LBCM ( 5- way CAN , 4- way LIN ) and RBCM ( 10 -way CAN , 14- way LIN (ultrasonic radar occupies 12 channels)), but they are considered to be considerable resources.
1. Information Transmitted by Automotive Ethernet
The types of data information transmitted on the vehicle and the requirements for the use of these data determine the characteristics of the transmission network and are also the basis for the selection or design of vehicle network standards. The data used and transmitted by the control system and information system on the car can be divided into control command parameters, safety and auxiliary driving information data, entertainment information (multimedia) data, and information service data.
1. Control command parameters
1 ) Low-bandwidth control applications: These in-vehicle control subsystems require low bandwidth and low quality of service requirements, including those control systems in the car that do not strictly require safety, such as electric rearview mirror folding and electric seats.
2 ) Real-time control applications: These in-vehicle systems have relatively low bandwidth requirements, but have higher requirements and strong real-time performance, such as suspension and braking systems, ABS , and traction control systems. The quality of these services is relatively high.
2. Safety and assisted driving information data
More and more modern cars are equipped with many built-in driver assistance safety systems, including adaptive cruise control systems using lidar or radar sensors, reversing radar and night pedestrian detection using infrared sensors. These data will affect driving safety and require high reliability and real-time performance.
3. Entertainment information (multimedia) data
In addition to traditional infotainment systems, more and more video and audio devices are installed in cars, all of which transmit multimedia data, requiring higher bandwidth and, depending on the application, higher service quality requirements. These include some passive safety systems, such as the 360- degree panoramic reversing camera for the driver, and active safety systems, such as lane departure detection using front and rear optical cameras. These are also typical information transmitted in Ethernet.
4. Information service data
In addition to traditional electronic map data for positioning and navigation, information service data will also see a significant increase in the amount of information similar to that transmitted over traditional Internet networks as vehicles are connected to the Internet and their ability to obtain and upload information improves. Even in a vehicle environment, Ethernet is still a suitable transmission network for this data from the perspective of user usage and industrial technology foundation. It is just that it has not been widely popularized due to the current high construction and R&D costs.
2. Performance of Automotive Ethernet
Compared with the traditional Ethernet application environment, the in-vehicle system has the following characteristics:
1 ) Small distribution range and high density.
2 ) The nodes are very different, the data types are diverse, and the requirements for data transmission bandwidth, real-time performance, reliability, etc. are complex and vary widely.
3 ) Industry technology and equipment must be standardized, with an open structure and flexible expansion.
4 ) It has higher requirements for hardware technical indicators and is more sensitive to costs. It is necessary to consider data collection, maintenance, wiring, and the list of collectable data and efficiency requirements in Ethernet data applications.
5 ) The hardware standards cannot be too low and must meet the standards of the automotive industry. The requirements for reliability, operating environment parameters, electromagnetic compatibility, environmental protection, and low power consumption should be as advanced as possible.
3. Advantages of using Ethernet
Although Ethernet was not originally designed for use in vehicle environments, due to its technical and application foundation in the field of computer networks, as well as the technical development and application needs in vehicles, Ethernet has some advantages that other standards cannot match after being installed in vehicles, mainly in the following aspects:
1. The technology is mature and there is a foundation for software and hardware development and production, which can shorten the R&D and production cycle, improve efficiency and reduce costs.
2. The application functions can be easily connected with other systems. Various network-based information application technologies and products can be transplanted to the vehicle-mounted system, similar to installing a computer.
3. In line with the development trend of in-vehicle information technology, the interconnection between the Internet of Vehicles and the Internet of Things must rely on Ethernet technology. Combined with 5G , there will be endless room for imagination in the future.
4. It is conducive to the entry of mature IT technology into the automotive industry and promotes the development of in-vehicle information technology, vehicle informatization and intelligence.
5. Users who are already familiar with Ethernet are more likely to accept information service functions and systems based on in-vehicle Ethernet.
6. It is conducive to the promotion of vehicle intelligence and various vehicle safety technologies based on information technology, thus opening the era of software-defined cars.
7. The hardware technology and cost that support the physical layer requirements of automotive Ethernet have been verified. The application of some automotive Ethernet systems has verified the feasibility of using Ethernet to build in-vehicle networks in vehicles, such as Porsche's in-vehicle wireless terminal:
Figure 2: Porsche Gateway Integrated Ethernet
4. Hardware Supporting Automotive Ethernet
With the development of automotive Ethernet technology, while the relevant protocol standards are being continuously improved, the hardware circuits supporting automotive Ethernet are also being developed. The hardware circuits of automotive Ethernet can also be divided into two categories, one is the automotive Ethernet communication medium chip, and the other is the processor that supports the automotive Ethernet communication protocol. Compared with general Ethernet, the characteristics of automotive Ethernet are that the use and storage temperature range, electromagnetic compatibility and other aspects meet the requirements of the automotive environment. Based on the expectation of the potential development of automotive information technology and products, not only traditional automotive electronic component manufacturers are actively developing automotive Ethernet technology and products, but some companies in the network industry are also actively joining the research and development of automotive Ethernet.
Figure 3: Terminal supporting Ethernet data collection and transmission (Sureide V81 )
Marvell and Micrel Semiconductor released standard-compliant Ethernet physical components for in-vehicle networks in 2012 ; Freescale launched the iMX 6 series application processors that support AVB, which facilitates the design of in-vehicle infotainment systems and integrated in-vehicle information services and infotainment platforms, and supports the development of true automotive Ethernet AVB through hardware and Ethernet switch solutions ; Surui Technology has developed the V81 series TBOX products based on iMX 6 , which are used in a large number of library function calls, vehicle control strategies, CAN message collection and transmission, 5G and Internet of Vehicles terminals; Xilinx and Harman International Group have jointly developed the CORETM IP core for field programmable gate arrays ( FPGAs ) platform; NXP has launched a product portfolio of automotive Ethernet transceiver TJA1100 and Ethernet switch SJA1105 , which has multiple hardware functions required for automotive Ethernet and complies with the standards specified by the OPEN Alliance; Broadcom's new BCM89811 physical transceiver has a wide range of application scenarios in automotive Ethernet connected to infotainment systems, advanced driver assistance systems, and telematics, instrument clusters, car audio head units and center console modules; Renesas's in-vehicle information terminal SOC R-CAR series, and in-vehicle AV BZ/A series have already achieved support for automotive Ethernet AVB .
5. Basic Process of Ethernet Access
Ethernet does not distinguish between master and slave nodes. In order to coordinate the transmission of information between nodes through the network line, the CSMA/CD mechanism is used to obtain the right to use the bus. Its basic working process is as follows:
1. When a node wants to send data through the network, it first checks whether the network is "idle" (no data is being transmitted in the network). If the network is "busy" (data is being transmitted in the network), it continues to query and wait.
2. When the network is idle, the node starts to send data. At this time, there may be multiple nodes waiting for this "idle" moment, and once "idle", they all start to send their own data.
3. If the sending node determines that there is an "obstruction", the data transmission will be interrupted and the sent data will be deleted. After a random wait, the network will resend a round of data.
The CSMA/CD network access method requires that the range of the Ethernet network is limited to a certain extent to control the maximum transmission time of the data packet. The data packet parameters are as follows:
Table: Ethernet packet parameters:
|
Serial number
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Field Name
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Length /B
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effect
|
illustrate
|
|
1
|
Preamble
|
7
|
Network nodes keep synchronized clock pulses
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The combination of the preamble and the delimiter has the function of clock synchronization
|
|
Start of frame delimiter
|
1
|
Packet start flag
|
|
2
|
Target Address
|
6
|
MAC address of the data receiving point
|
|
|
3
|
Source Address
|
6
|
MAC address of the data sending point
|
|
|
4
|
Type / Length
|
2
|
Ethernet data guards the exact length of the data
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Range from 0-1500
|
|
5
|
data
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46-1500
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Data Information
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When the data is less than 46 bytes, padding is required.
|
|
6
|
Frame Check Sequence
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4
|
Check code
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Used to verify data at the receiving end
|
6. Applications based on automotive Ethernet
Automobile manufacturers have begun to pay more and more attention to the application technology of in-vehicle Ethernet. Many mainstream automobile manufacturers have joined in the formulation of relevant standards for in-vehicle Ethernet and promoted its popularization.
The BMW X5 uses in-vehicle Ethernet technology that can achieve a transmission rate of 100Mbit/s in the path connecting the peripheral monitoring camera module and the ECU to transmit images , and uses Ethernet in the transmission path of the information communication system connecting the in-vehicle information terminal and the central gateway.
Toyota has developed Ethernet-based in-vehicle LAN interface specifications and has begun activities toward international standardization in collaboration with Renesas Electronics and Broadcom.
In Ethernet data transmission technology, a pair of UTP (unshielded twisted pair) can be used to achieve a transmission rate of 100Mbit/s . The physical layer uses NXP TJA1100 as the interface between the analog transmission medium and the data MAC controller to meet the EMC requirements of the automotive industry and can support cable lengths of up to 25M . The 2014 and 2015 BMW X5 , 2015 Jaguar XJ and 2015 Volkswagen Passat all use automotive Ethernet technology.
The application of in-vehicle Ethernet in advanced driver assistance systems effectively solves the needs of information transmission and fusion. The latest ADAS systems usually use high-speed Ethernet to build data links and connect multiple high dynamic range megapixel cameras.
The communication between vehicle-mounted equipment and devices mainly adopts wired vehicle-mounted networks . Depending on the information transmission, CAN , LIN , MOST , FlexRay , vehicle-mounted Ethernet and other networks are used . For some devices, since the components to be communicated are relatively moving, it is impossible or inconvenient to connect directly through wires, so wireless transmission is used, such as tire pressure monitoring systems .
That’s all .
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