At present, the network is full of such a voice "Ethernet will replace the CAN bus to become the only bus of the car" related articles can be easily searched on the search engine. Is this true?
First tell the answer at the beginning of the article:
As far as the current technology of mankind is concerned, Ethernet can only be used as a CAN bus in the vehicle, and there is no possibility of replacing the CAN bus.
If you are not satisfied, just know the conclusion, know it and know why, then read the next article. This may take you up to 3 minutes, but it can tell you why you got this answer.
As we all know, as a standard open network Ethernet transmission signal, compared with the CAN bus, it has the advantages of high transmission rate and long transmission distance. And the technology is quite mature, and there are more people in control. At present, even if it is already used in automobiles, it is only used to transmit high-speed signals such as radar and video. Why can't I build a car that uses Ethernet bus communication? The main reasons are as follows:
1, CAN network securityFrom the perspective of the connection of the network, the CAN bus is connected by physical signals, and the Ethernet is connected by a switch. The switch is necessary in the Ethernet connection, and the entire network will crash once the switch is poor. It is too much to put the security of the entire network into a switch that is too weak. If you set up redundant standby, you will have to increase the cost. In contrast, the structure of the CAN bus is very simple, only need to pull two lines, simple and stable. For the safety first car, the CAN bus is undoubtedly more suitable. Moreover, Ethernet adopts a timeout retransmission mechanism, and the failure of a single node can easily spread to the entire network. Compared with the hierarchical arbitration system of the CAN bus, it is inferior.
We mentioned the switch in terms of security. Yes, the existence of an Ethernet network switch is indispensable, and the number of nodes in the modern automotive network is astounding. If all Ethernet is used for communication, one or several switches with super-multiple interfaces are required. Moreover, as a product such as a car that is highly valued for safety, the stability and quality requirements of the switch must be extremely high, so that the increase in cost is not a star and a half. The ever-increasing cost is not what the owners of car factories are willing to see.
If you have seen the movie "Speed ​​and Passion 8", I believe you must remember the plot of the "zombie car". The villain controlled a large number of cars with ''autopilot'' functions in New York City to rush to the streets to besiege Russian ambassadors holding important documents. Although the plot of entertainment movies can't stand the scrutiny, cars that can be controlled by the Internet may indeed be hacked by hackers. As a standard open network system, Ethernet has good compatibility and interoperability, and has strong resource sharing capabilities. It can easily complete information and resource sharing operations. Undoubtedly, it reduces the cost of criminals and increases the operability. Relatively speaking, the CAN bus is a dedicated field bus, which is difficult for hackers to enter.
Finally let us use the table to summarize:
In this way, replacing the CAN bus with Ethernet has become an impossible task. However, the CAN bus transmission speed is slow and the transmission distance is limited. It is really there. Is there a suitable solution that can be upgraded? As far as the current technology is concerned, the vehicle Ethernet is the backbone, and the communication method of CANFD as a subsystem can be described as a collection of “ten thousand pets in oneâ€. It not only retains the real-time and safe features of CAN, but also enhances the communication speed and transmission distance, while also ensuring cost control. It is the best choice for "fish and bear paw platter".
CAN-FD greatly expands the length of the data field. The DLC supports a maximum of 64 bytes. When the DLC is less than or equal to 8, it is the same as the original CAN bus. When it is greater than 8, there is a nonlinear increase, so the largest The data field can be up to 64 bytes in length.
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