Vehicle-mounted controller local area network bus device and control method thereof

Abstract

The present invention provides an on-vehicle controller area network bus device and a control method thereof. The on-vehicle controller area network bus device comprises: an automotive-grade single-chip microcomputer chip and four CAN x channels thereon: CAN 1, CAN 2, CAN 3, and CAN 4, where CAN x represents a controller area network or a controller area network with adjustable data rate, wherein both CAN 1 and CAN 2 are connected to a controllable passive normally closed relay. The present invention solves the problem of the stump effect that occurs when a high-speed CAN bus is physically modified. By using the device provided by the present invention, it is possible to avoid introducing too many branches when modifying the CAN bus, ensuring that each isolated controller maintains the bus topology, thereby meeting modification requirements while ensuring communication stability and signal quality.

Description

Technical Field

[0001] The present invention belongs to the field of electronic communication technology, and in particular relates to a vehicle-mounted controller area network (CAN) bus device modified by hardware isolation and software middleman technology and a control method thereof. Background Art

[0002] With the continued development of the economy and the acceleration of urbanization, cars have become the preferred means of transportation for Chinese consumers. This trend has also driven the rapid development of the automotive industry. Both traditional fuel vehicles and new energy electric vehicles have received widespread attention and application in the Chinese market.

[0003] ADAS, or Advanced Driver Assistance Systems, has become the core of contemporary automotive technology. With technological advancements, ADAS functionality has gradually expanded, evolving from initial parking assistance and collision warnings to autonomous driving, providing drivers with a safer and more convenient driving experience. However, this has come with a dramatic increase in system complexity, placing higher demands on the development and verification of system hardware and software.

[0004] To cope with the rapid changes and competitive pressures of the automotive market, many automakers aim to complete new vehicle development in a short period of time. This often leads to the development and verification of new automotive controllers without a complete automotive hardware platform. To achieve this, a common approach involves a series of modifications and commissioning based on existing legacy vehicle platforms.

[0005] Retrofitting older vehicle models to accommodate new controllers is a complex and challenging task. First, such modifications often significantly impact the original vehicle's bus topology, hindering overall vehicle communication and functionality. More importantly, such modifications can affect the vehicle's CAN bus topology. As a key technology for internal automotive communications, any changes to the CAN bus structure can have unpredictable consequences.

[0006] With the advancement of technology, a high-speed CAN technology—Controller Area Network with Flexible Data Rate (CANFD)—has been adopted by more and more vehicle models. This high-speed communication technology places very high demands on line signal quality. Only by ensuring high-quality signal transmission can the controller function properly. However, methods based on physical modification struggle to meet this requirement, which not only affects development and testing efficiency but, more seriously, poses a threat to the safety of testers if controller failure occurs due to signal quality issues during ADAS testing.

[0007] To summarize, when retrofitting older vehicle models to accommodate new controllers, the original vehicle's bus topology often needs to be modified. This modification can introduce new communication issues, leading to unstable communication between the original and new controllers. This increases the complexity of development and verification, potentially preventing certain functions from being implemented or degrading performance. This can also hinder communication and functional implementation throughout the vehicle, increasing the failure rate. Furthermore, due to the high signal quality requirements of CAN FD technology, physical modifications may not be sufficient to meet the demands of this high-speed communication technology. During the physical modification and debugging process, issues with the bus topology and signal quality can lead to system failures or controller failures, potentially preventing the controller from functioning properly and causing functional failures. During ADAS testing, poor signal quality can cause controller failure, posing a threat to the safety of testers. Consequently, debugging and optimization can require additional time and resources, extending the development cycle and increasing the risk during testing. Summary of the Invention

[0008] In view of the above problems, the present invention provides a vehicle-mounted controller local area network bus device and a control method thereof.

[0009] The vehicle-mounted controller area network bus device provided by the present invention includes: a vehicle-grade single-chip microcomputer chip and four CAN x channels thereon: CAN 1, CAN 2, CAN 3 and CAN 4, where CAN x represents a controller area network or a controller area network with adjustable data rate.

[0010] in,

[0011] The channels CAN 1 and CAN 2 are both connected to controllable passive normally closed relays.

[0012] further,

[0013] The four CAN x channels each include a first high-speed controller area network bus CAN-H and a second high-speed controller area network bus CAN-L, namely:

[0014] The channel CAN 1 includes buses CAN1-H and CAN1-L;

[0015] The channel CAN 2 includes buses CAN2-H and CAN2-L;

[0016] The channel CAN 3 includes buses CAN3-H and CAN3-L;

[0017] The channel CAN 4 includes buses CAN4-H and CAN4-L.

[0018] further,

[0019] The controllable passive normally closed relays are connected to the buses CAN1-H and CAN1-L as well as CAN2-H and CAN2-L.

[0020] further,

[0021] In the power-off state, the bus CAN1-H and CAN2-H are data-connected, and the bus CAN1-L and CAN2-L are data-connected;

[0022] When the power is on, the data between the channels CAN 1 and CAN 3 is connected, and the data between the channels CAN 2 and CAN 4 is connected.

[0023] further,

[0024] When powered on, the bus CAN1-H and CAN3-H are data-connected, the bus CAN1-L and CAN3-L are data-connected, the bus CAN2-H and CAN4-H are data-connected, and the bus CAN2-L and CAN4-L are data-connected.

[0025] further,

[0026] The automotive-grade single-chip microcomputer chip is provided with buses I-CAN1-H and I-CAN1-L, I-CAN2-H and I-CAN2-L, I-CAN3-H and I-CAN3-L, I-CAN4-H and I-CAN4-L,

[0027] The buses I-CAN1-H and I-CAN1-L are connected to the buses CAN1-H and CAN1-L respectively through the passive normally closed relays.

[0028] The buses I-CAN2-H and I-CAN2-L are connected to the buses CAN2-H and CAN2-L respectively via the passive normally closed relays.

[0029] When the passive normally closed relay is powered, the bus CAN1-H is connected to I-CAN1-H, the bus CAN1-L is connected to I-CAN1-L, the bus CAN2-H is connected to I-CAN2-H, and the bus CAN2-L is connected to I-CAN2-L.

[0030] When the passive normally closed relay is not energized, the bus CAN1-H and I-CAN1-H are disconnected, the bus CAN1-L and I-CAN1-L are disconnected, the bus CAN2-H and I-CAN2-H are disconnected, and the bus CAN2-L and I-CAN2-L are disconnected.

[0031] The automotive-grade single-chip microcomputer chip is also equipped with buses I-CAN3-H and I-CAN3-L, I-CAN4-H and I-CAN4-L.

[0032] The buses I-CAN3-H and I-CAN3-L are connected to the buses CAN3-H and CAN3-L respectively, and the buses I-CAN4-H and I-CAN4-L are connected to the buses CAN4-H and CAN4-L respectively.

[0033] further,

[0034] Each of the four CAN x channels is provided with a 120-ohm terminal resistor that can be controlled by a dial switch, i.e., program-controlled, to adapt to different network topologies.

[0035] further,

[0036] The terminal resistors of the channels CAN 1 and CAN 2 are both arranged between the automotive-grade single-chip microcomputer chip and the passive normally closed relay.

[0037] The present invention also provides a control method for the above-mentioned vehicle-mounted controller local area network bus device, which comprises:

[0038] Based on the following two typical working modes:

[0039] 1. Passive working mode,

[0040] In the passive working mode, no external power supply is required. The passive normally closed relay in the vehicle controller local area network bus device is controlled by the dial control, so that the connection between the buses CAN1-H and CAN2-H, and the connection between CAN1-L and CAN2-L are maintained to ensure the continuity of the original vehicle network;

[0041] 2. Active forwarding mode,

[0042] In the active forwarding mode, the vehicle-mounted controller area network bus device requires an external power supply. The passive normally closed relay is controlled by the dial control to connect channels CAN 1 and CAN 2 with the corresponding interfaces of the vehicle-standard single-chip microcomputer chip. The vehicle-standard single-chip microcomputer chip reads and filters the data received from the channels CAN 1 and CAN 2, constructs a new controller area network message, sends it, and forwards it to channels CAN 3 and CAN 4. At the same time, the data received from the channels CAN 3 and CAN 4 are forwarded to the channels CAN 1 and CAN 2.

[0043] Further, including:

[0044] In the passive working mode, the automotive-grade MCU chip does not work, and all data flows directly through the channels CAN 1 and CAN 2 without any processing.

[0045] In the active forwarding mode, the automotive-grade single-chip microcomputer chip is in working state, and the automotive-grade single-chip microcomputer chip dynamically forwards data and transmits data between the 4 CAN x channels according to actual needs.

[0046] The in-vehicle controller area network bus device provided by this invention solves the stub effect problem that occurs when physically modifying a high-speed CAN bus. By using the device provided by this invention, it is possible to avoid introducing excessive branch lines when modifying the CAN bus, ensuring that each isolated controller maintains the bus topology, thus meeting modification requirements while ensuring stable communication and signal quality.

[0047] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 It shows a schematic structural diagram of a vehicle-mounted CAN bus device according to an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of control signals in a control method for a vehicle-mounted CAN bus device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", "third", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship. "Multiple" appearing in this application refers to two or more (including two).

[0053] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] Figure 1 This is a schematic diagram of the structure of the vehicle-mounted CAN bus device provided by the present invention. Figure 1The on-board CAN bus device includes a vehicle-grade single-chip microcontroller chip and four CAN / CANFD (hereinafter referred to as CAN x) channels thereon: CAN 1, CAN 2, CAN 3, and CAN 4. These four channels can be accessed separately by a multi-core central processing unit (CPU) to control the relevant data transmission. Each CAN x channel includes a first high-speed CAN bus CAN-H and a second high-speed CAN bus CAN-L, that is, channel CAN 1 includes buses CAN1-H and CAN1-L, channel CAN 2 includes buses CAN2-H and CAN2-L, channel CAN 3 includes buses CAN3-H and CAN3-L, and channel CAN 4 includes buses CAN4-H and CAN4-L. Controllable passive normally closed relays are connected to channels CAN 1 and CAN 2, that is, controllable passive normally closed relays are connected to buses CAN1-H and CAN1-L, as well as CAN2-H and CAN2-L. By connecting the CAN-H and CAN-L buses of channels CAN 1 and CAN 2 using a passive normally closed relay, the original vehicle network (referred to as the original vehicle network) can be maintained when power is off (i.e., the passive normally closed relay is off). In this state, data is communicated between buses CAN1-H and CAN2-H, and between buses CAN1-L and CAN2-L. When power is supplied (i.e., the passive normally closed relay is on), data is communicated between channels CAN 1 and CAN 3 (i.e., data is communicated between buses CAN1-H and CAN3-H, and between buses CAN1-L and CAN3-L), and data is communicated between channels CAN 2 and CAN 4 (i.e., data is communicated between buses CAN2-H and CAN4-H, and between buses CAN2-L and CAN4-L).

[0055] Figure 1 The diagram shows four independent CAN x channels: CAN 1, CAN 2, CAN 3, and CAN 4. CAN 1 and CAN 2 are specifically designed to connect to different vehicle controllers. The vehicle controller itself has four high-speed CAN buses corresponding to CAN1-H and CAN1-L, and CAN2-H and CAN2-L, for one-to-one connection. CAN 3 and CAN 4 provide access points for external devices or other applications. Specifically, CAN 3 connects to a new control component, replacing CAN 2 and its connected controller, while CAN 4 connects to a new control component, replacing CAN 1 and its connected controller. Therefore, only passive normally closed relays are required on CAN 1 and CAN 2.

[0056] In practical applications, the number of independent CAN x channels can be selected based on specific operating conditions. When the system is powered on and controlled by the vehicle's microcontroller unit (MCU), a passive normally closed relay can be switched to connect or isolate the vehicle controller from the automotive-grade single-chip microcontroller chip. This is specifically reflected in the connection between the CAN1-H and CAN1-L buses and the I-CAN1-H and I-CAN1-L buses, and between the CAN2-H and CAN2-L buses and the I-CAN2-H and I-CAN2-L buses. I-CAN1-H and I-CAN1-L correspond to the CAN1-H and CAN1-L buses on the automotive-grade single-chip microcontroller chip, respectively, while I-CAN2-H and I-CAN2-L correspond to the CAN2-H and CAN2-L buses on the automotive-grade single-chip microcontroller chip. Buses I-CAN1-H and I-CAN1-L are connected to buses CAN1-H and CAN1-L, respectively, through passive normally closed relays. Buses I-CAN2-H and I-CAN2-L are connected to buses CAN2-H and CAN2-L, respectively, through passive normally closed relays. When the passive normally closed relays are energized, buses CAN1-H and I-CAN1-H are connected, CAN1-L and I-CAN1-L are connected, CAN2-H and I-CAN2-H are connected, and CAN2-L and I-CAN2-L are connected. The automotive-grade MCU also features buses I-CAN3-H and I-CAN3-L, and I-CAN4-H and I-CAN4-L. When the passive normally closed relay is de-energized, buses CAN1-H and I-CAN1-H are disconnected, CAN1-L and I-CAN1-L are disconnected, CAN2-H and I-CAN2-H are disconnected, and CAN2-L and I-CAN2-L are disconnected. Buses I-CAN3-H and I-CAN3-L connect to buses CAN3-H and CAN3-L, respectively, while buses I-CAN4-H and I-CAN4-L connect to buses CAN4-H and CAN4-L, respectively.

[0057] In practical applications, the bus of channel CAN 1 is connected to the CAN bus of the original vehicle controller, and the bus of channel CAN 2 is connected to the original vehicle CAN network. In passive operation, channels CAN 1 and CAN 2 are conductive, maintaining the original vehicle topology. In active operation, the controller connected to channel CAN 1 connects to channel CAN 1 alone, and then connects data to channel CAN 3, without connecting to channel CAN 2, achieving a point-to-point connection.

[0058] The automotive-grade microcontroller chip manages and controls the four independent CAN x channels, enabling dynamic data forwarding. By controlling the passive normally closed relays, the automotive-grade microcontroller chip enables different vehicle controllers to communicate with each other when needed, while ensuring no interference with the original vehicle network or other components. This means the automotive-grade microcontroller chip implements bus isolation and forwarding functions, ensuring the stability and reliability of the in-vehicle CAN bus device provided by the present invention in an automotive environment. Furthermore, the automotive-grade microcontroller chip features four CAN x ports corresponding to the four independent CAN x channels, enabling communication with multiple devices or systems and providing a physical foundation for point-to-point connection and isolation. The automotive-grade microcontroller chip can dynamically forward data between these four CAN buses as needed, allowing different vehicle controllers to communicate with each other as needed without disrupting the operation of other components.

[0059] When a new vehicle controller is added, the in-vehicle CAN bus device provided by the present invention connects it to the original vehicle controller in a point-to-point manner, effectively ensuring signal quality and avoiding issues caused by changes in physical topology. Furthermore, when a vehicle controller connected to the in-vehicle CAN bus device provided by the present invention needs to be isolated by controlling a passive normally closed relay, the in-vehicle CAN bus device can maintain the original bus topology, avoiding the "stub effect."

[0060] In the in-vehicle CAN bus device provided by this invention, each of the four independent CAN x channels is equipped with a 120-ohm terminal resistor that can be controlled by a DIP switch, i.e., program, to adapt to different network topologies. The terminal resistors for channels CAN 1 and CAN 2 are both located between the automotive-grade microcontroller chip and a passive normally closed relay.

[0061] In practical applications of the in-vehicle CAN bus device provided by this invention, the vehicle controller to be isolated is connected near the vehicle's Electronic Control Unit (ECU). This allows for direct disconnection from the vehicle controller's CAN transceiver during isolation, reducing data cable length. Channel CAN 1 is directly connected to the ECU, while channel CAN 2 is connected to a gateway, enabling the topology of the on-board controller to be changed by controlling passive normally closed relays. Furthermore, two twisted-pair cables can be extended through channels CAN 3 and CAN 4 to new control locations within the vehicle, such as the trunk, passenger glove box, or rear seat.

[0062] Figure 2 This is a schematic diagram of control signals in the control method of the vehicle-mounted CAN bus device provided by the present invention. Figure 2The following describes a control method for a vehicle-mounted CAN bus device provided by the present invention. The control method is based on the following two typical working modes:

[0063] 1. Passive working mode.

[0064] In this mode, the vehicle-mounted CAN bus device does not require external power supply.

[0065] In the state of no power, the passive normally closed relay in the vehicle CAN bus device is controlled by the dial control, so that the CAN-H and CAN-L of channels CAN 1 and CAN 2, that is, the connection between CAN1-H and CAN2-H, and the connection between CAN1-L and CAN2-L are maintained to ensure the continuity of the original vehicle network.

[0066] When there is no power, the automotive-grade microcontroller chip does not work, and all data flows directly through channels CAN 1 and CAN 2 without any processing.

[0067] The advantage of this mode is that it will not affect the normal operation of the original vehicle network, and can ensure that when the external power supply is disconnected or fails, the communication of the vehicle using the on-board CAN bus device remains undisturbed.

[0068] 2. Active forwarding mode.

[0069] In this mode, the vehicle-mounted CAN bus device requires external power supply and the vehicle-grade microcontroller chip is in working condition.

[0070] Through DIP control, the passive normally closed relay is controlled to connect channels CAN 1 and CAN 2 to the corresponding interfaces of the automotive-grade microcontroller chip. The automotive-grade microcontroller chip uses the general purpose input / output port (GPIO) to isolate and forward the data stream from the original vehicle network.

[0071] The automotive-grade MCU reads, filters, constructs, and transmits data received from channels CAN 1 and CAN 2, processes the data, and forwards it to channels CAN 3 and CAN 4. It also forwards data received from channels CAN 3 and CAN 4 to CAN 1 and CAN 2. Data received from channels CAN 1 to CAN 4 includes the CAN identity (ID), data length (DLC), IDE (extended frame flag), remote flag (RTR), high-speed transmit switch flag (BRS), and data content.

[0072] In this mode, the automotive-grade microcontroller chip can dynamically forward data and transmit data between the four CAN channels according to actual needs.

[0073] In this mode, the vehicle-mounted CAN bus device enables different vehicle controllers connected thereto to communicate with each other when needed, while ensuring that the normal operation of the original vehicle network or other parts is not interfered with.

[0074] Furthermore, the resistance values ​​of the four terminal resistors are controlled by dial control to adapt to different network topologies. The terminal resistors are adjustable and the full value is 120 ohms.

[0075] In summary, the vehicle-mounted CAN bus device and control method thereof provided by the present invention can achieve the following effects:

[0076] Maintaining the original vehicle network topology: This invention can ensure that the original vehicle network topology is not affected when modifying the car, thereby reducing problems such as signal reflection and interference introduced by physical modifications.

[0077] Reducing the "stub effect": By using this technology, the "stub effect" caused by the added branches during the modification process can be avoided, which helps to keep the CAN network stable and efficient.

[0078] Improved safety: In the absence of power, a passive normally closed relay ensures connectivity between CAN 1 and CAN 2, which helps ensure continuity of communication in critical situations.

[0079] Strong adaptability: Through the dial control of the terminal resistor, it can adapt to various network topologies, allowing the device to be used in different vehicles and configurations.

[0080] Simplified retrofit process: Traditional physical retrofits may involve complex cable rerouting, connection, and testing. This solution provides retrofit engineers with an integrated solution that simplifies the entire retrofit process.

[0081] Cost Savings: By reducing the complexity of physical modifications, you can save significant time and labor costs while reducing potential damage due to incorrect wiring or connection errors.

[0082] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vehicle-mounted controller local area network bus device, characterized in that: include: It includes a car-grade microcontroller chip and its four CAN x channels: (CAN 1), (CAN 2), (CAN 3) and (CAN 4). CAN x stands for controller area network or data rate adjustable controller area network. in, The channels (CAN 1) and (CAN 2) are both connected with controllable passive normally closed relays; The four CAN x channels each include a first high-speed controller area network bus CAN-H and a second high-speed controller area network bus CAN-L, namely: The channel (CAN 1) includes buses (CAN1-H) and (CAN1-L); The channel (CAN 2) includes buses (CAN2-H) and (CAN2-L); The channel (CAN 3) includes buses (CAN3-H) and (CAN3-L); The channel (CAN 4) includes buses (CAN4-H) and (CAN4-L); The channels (CAN 1) and (CAN 2) are used to connect to different vehicle controllers respectively. The vehicle controller itself is provided with a 4-way controller high-speed CAN bus corresponding to buses (CAN1-H) and (CAN1-L), and buses (CAN2-H) and (CAN2-L) for corresponding one-to-one connection; the channels (CAN3) and (CAN4) are used to provide access points for external devices or other applications, that is, channel (CAN3) is used to connect a new control component, the new control component is used to replace channel (CAN2) and the controller connected to the channel, and channel (CAN4) is used to connect another new control component to replace channel (CAN1) and the controller connected to the channel; In the power-off state, the bus (CAN1-H) and (CAN2-H) are data-connected, and the bus (CAN1-L) and (CAN2-L) are data-connected; When the power is on, the data between the channels (CAN 1) and (CAN 3) is connected, and the data between the channels (CAN 2) and (CAN4) is connected. In the state with power supply, the bus (CAN1-H) and (CAN3-H) are data-connected, the bus (CAN1-L) and (CAN3-L) are data-connected, the bus (CAN2-H) and (CAN4-H) are data-connected, and the bus (CAN2-L) and (CAN4-L) are data-connected, that is, in the active working condition, the controller connected to the channel (CAN1) is connected to the channel (CAN1) alone, and then the data is connected to the channel (CAN3) without being connected to the channel (CAN2), so that the new control component connected to the channel (CAN3) is connected to the vehicle controller connected to the channel (CAN1) in a point-to-point manner; The controllable passive normally closed relay is connected to the buses (CAN1-H) and (CAN1-L) as well as (CAN2-H) and (CAN2-L); The automotive-grade single-chip microcontroller chip is provided with buses (I-CAN1-H) and (I-CAN1-L), (I-CAN2-H) and (I-CAN2-L), (I-CAN3-H) and (I-CAN3-L), (I-CAN4-H) and (I-CAN4-L). The buses (I-CAN1-H) and (I-CAN1-L) are connected to the buses (CAN1-H) and (CAN1-L) respectively via the passive normally closed relays. The buses (I-CAN2-H) and (I-CAN2-L) are connected to the buses (CAN2-H) and (CAN2-L) respectively via the passive normally closed relays. When the passive normally closed relay is energized, the bus (CAN1-H) is connected to (I-CAN1-H), the bus (CAN1-L) is connected to (I-CAN1-L), the bus (CAN2-H) is connected to (I-CAN2-H), and the bus (CAN2-L) is connected to (I-CAN2-L). When the passive normally closed relay is not energized, the bus (CAN1-H) and (I-CAN1-H) are disconnected, the bus (CAN1-L) and (I-CAN1-L) are disconnected, the bus (CAN2-H) and (I-CAN2-H) are disconnected, and the bus (CAN2-L) and (I-CAN2-L) are disconnected. The automotive-grade MCU chip is also equipped with buses (I-CAN3-H) and (I-CAN3-L), (I-CAN4-H) and (I-CAN4-L). The buses (I-CAN3-H) and (I-CAN3-L) are respectively connected to the buses (CAN3-H) and (CAN3-L), and the buses (I-CAN4-H) and (I-CAN4-L) are respectively connected to the buses (CAN4-H) and (CAN4-L); Each of the four CAN x channels is equipped with a 120 ohm terminal resistor that can be controlled by a dial switch, i.e., program-controlled, to adapt to different network topologies; The terminal resistors of the channels (CAN 1) and (CAN 2) are both arranged between the automotive-grade single-chip microcontroller chip and the passive normally closed relay.

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