CAN communication circuit, terminal resistance matching method and CAN communication system

Abstract

The invention is suitable for the technical field of CAN communication, and provides a CAN communication circuit, a terminal resistance matching method and a CAN communication system. In the communication circuit, a CANH end of a CAN transceiver is connected with a first end of a first resistance filtering branch and a first port of an external circuit interface, a second end of the first resistance filtering branch is grounded, and a third end of the first resistance filtering branch is connected with a third port of the external circuit interface; the CANL end of the CAN transceiver is connected with the first end of the second resistance filtering branch and the second port of the external circuit interface, the second end of the second resistance filtering branch is grounded, and the third end of the second resistance filtering branch is connected with the fourth port of the external circuit interface; and when the CANH end and the CANL end of the CAN transceiver are connected to the terminal resistor, the third port and the fourth port are in short circuit. According to the invention, the CAN communication circuit can be accessed to the terminal resistor without changing the hardware structure of the CAN communication circuit, the hardware circuit of the CAN communication circuit is unified, and the hardware management complexity is reduced.

Description

Technical Field

[0001] The present application relates to the field of CAN communication technology, and in particular to a CAN communication circuit, a terminal resistance matching method and a CAN communication system. Background Art

[0002] CAN (Controller Area Network) communication, as a communication method with outstanding reliability, real-time performance and flexibility, is widely used in the automotive field. As the number of control modules in vehicle systems increases, CAN communication also increases.

[0003] In CAN communication, terminal resistors play an important role, preventing signal reflections and improving anti-interference capabilities. Whether a CAN communication circuit incorporates terminal resistors typically depends on the actual application scenario and specific requirements. In different application scenarios, adapting the inclusion of terminal resistors requires changes to the CAN communication circuit's hardware structure, complicating hardware management and increasing management costs. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a CAN communication circuit, a terminal resistance matching method and a CAN communication system to solve the technical problem that when matching terminal resistance in related technologies, the hardware structure needs to be changed, resulting in complex hardware management and increased management costs.

[0005] In a first aspect, an embodiment of the present application provides a CAN communication circuit, comprising: a CAN transceiver, a first resistor filter branch, a second resistor filter branch, and an external circuit interface; the external circuit interface is a plug-in terminal;

[0006] The CANH end of the CAN transceiver is connected to the first end of the first resistor filter branch and the first port of the external circuit interface, the second end of the first resistor filter branch is grounded, and the third end of the first resistor filter branch is connected to the third port of the external circuit interface;

[0007] The CANL terminal of the CAN transceiver is connected to the first end of the second resistor filter branch and the second port of the external circuit interface, the second end of the second resistor filter branch is grounded, and the third end of the second resistor filter branch is connected to the fourth port of the external circuit interface;

[0008] When the CANH terminal and the CANL terminal of the CAN transceiver are connected to the terminal resistor, the third port and the fourth port of the external circuit interface are short-circuited.

[0009] In a possible implementation manner of the first aspect, the first resistance filter branch includes a first resistor and a first capacitor, and the second resistance filter branch includes a second resistor and a second capacitor;

[0010] The CANH terminal of the CAN transceiver is connected to one end of the first resistor and the first port of the external circuit interface, the other end of the first resistor is connected to one end of the first capacitor and the third port of the external circuit interface; the other end of the first capacitor is grounded;

[0011] The CANL end of the CAN transceiver is connected to one end of the second resistor and the second port of the external circuit interface, the other end of the second resistor is connected to one end of the second capacitor and the fourth port of the external circuit interface; the other end of the second capacitor is grounded.

[0012] In a possible implementation manner of the first aspect, when the CANH terminal and the CANL terminal of the CAN transceiver are not connected to the terminal resistor, the third port and the fourth port of the external circuit interface are unconnected.

[0013] In a possible implementation of the first aspect, the CAN communication circuit further includes: a common mode inductor;

[0014] The CANH terminal of the CAN transceiver is connected to the first input terminal of the common-mode inductor, and the first output terminal of the common-mode inductor is connected to one end of the first resistor;

[0015] The CANL terminal of the CAN transceiver is connected to the second input terminal of the common-mode inductor, and the second output terminal of the common-mode inductor is connected to one end of the second resistor.

[0016] In a possible implementation manner of the first aspect, the first resistor and the second resistor have the same resistance value, and the first capacitor and the second capacitor have the same capacitance value.

[0017] In a possible implementation manner of the first aspect, the CANH terminal of the CAN transceiver is connected to the first port via a high-level signal line, and the CANL terminal of the CAN transceiver is connected to the second port via a low-level signal line.

[0018] In a possible implementation manner of the first aspect, the high-level signal line and the low-level signal line are parallel and have the same length.

[0019] In a second aspect, an embodiment of the present application provides a terminal resistance matching method for a CAN communication circuit, which is applied to the CAN communication circuit according to any one of the first aspects, the method comprising:

[0020] When the terminal resistors are connected to the CANH and CANL terminals of the CAN transceiver, the third port and the fourth port of the external circuit interface are short-circuited.

[0021] In a possible implementation of the second aspect, the method further includes:

[0022] When the CANH terminal and the CANL terminal of the CAN transceiver are not connected to the terminal resistor, the third port and the fourth port of the external circuit interface are empty.

[0023] In a third aspect, an embodiment of the present application provides a CAN communication system, which includes a CAN controller and a CAN communication circuit as described in any one of the first aspects.

[0024] It can be understood that the beneficial effects of the second to third aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0025] The CAN communication circuit, terminal resistance matching method and CAN communication system provided in the embodiments of the present application are provided with a first resistance filter branch and a second resistance filter branch for filtering the CANH signal and the CANL signal separately. When a terminal resistor needs to be connected between the CANH end and the CANL end of the CAN transceiver, the two resistance filter branches are short-circuited by short-circuiting the corresponding ports of the external circuit interface, so that the resistors in the first resistance filter branch and the second resistance filter branch are connected in series between the two CAN signal lines and connected to the CAN communication circuit as terminal resistors. In this way, the CAN communication circuit can be connected to the terminal resistor without changing the hardware structure of the CAN communication circuit, thereby unifying the hardware circuit of the CAN communication circuit and reducing the complexity of hardware management. In addition, since the external circuit interface is a plug-in terminal block, it has high vibration resistance, ensures the stability and reliability of the CAN communication circuit, and meets the requirements of small size and high vibration resistance.

[0026] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 This is a connection diagram of a CAN communication circuit provided by an embodiment of the present application;

[0029] Figure 2 This is a connection diagram of a CAN communication circuit provided in another embodiment of the present application. DETAILED DESCRIPTION

[0030] The present application will be described more clearly below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the function of the present application, but are not intended to limit the present application in any form. It should be noted that those skilled in the art may make a number of modifications and improvements without departing from the concept of the present application. These all fall within the scope of protection of the present application.

[0031] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0032] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0033] In the description of this application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0034] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0035] In addition, the “plurality” mentioned in the embodiments of the present application should be interpreted as two or more.

[0036] In CAN communication, terminal resistors play an important role, preventing signal reflections and improving anti-interference capabilities. Whether a CAN communication circuit incorporates terminal resistors is typically determined based on the actual application scenario and specific requirements. In different application scenarios, adapting the terminal resistors to the desired configuration requires changes to the CAN communication circuit's hardware structure, complicating hardware management and increasing management costs. This is especially true when multiple CAN communication circuits are involved, where hardware management becomes even more complex.

[0037] In addition, the inventors found that if the terminal resistor is connected by adding a dip switch or a jumper cap, the dip switch is unstable and bulky, and the jumper cap has poor vibration resistance. Both may cause the CAN communication circuit to be unstable and unreliable, affecting the normal operation of the CAN communication circuit.

[0038] In order to solve the problem of matching terminal resistance, reduce the complexity of hardware management, unify the hardware circuit of the CAN communication circuit, and ensure the stability and reliability of the CAN communication circuit, the inventors have discovered that two resistance filter branches can be set up respectively to filter the CANH signal and the CANL signal separately. When a terminal resistor needs to be connected between the CANH end and the CANL end of the CAN transceiver, the two resistance filter branches are short-circuited by short-circuiting the corresponding ports of the external circuit interface, so that the resistors in the two resistance filter branches are connected in series between the two CAN signal lines, that is, the CAN communication circuit is connected to the terminal resistor. In this way, the hardware circuit of the CAN communication circuit can be unified and the complexity of hardware management can be reduced.

[0039] At the same time, since there is no need to set a dip switch or jumper cap, the stability and reliability of the CAN communication circuit are guaranteed, meeting the requirements of small size and high vibration resistance.

[0040] Figure 1 This is a connection diagram of the CAN communication circuit provided by an embodiment of the present application. Figure 1 As shown, the CAN communication circuit may include: a CAN transceiver U1, a first resistor filter branch L1, a second resistor filter branch L2 and an external circuit interface Z1, wherein the external circuit interface Z1 is a plug-in terminal.

[0041] The CANH terminal of the CAN transceiver U1 is connected to the first end of the first resistor filter branch L1 and the first port P1 of the external circuit interface Z1, the second end of the first resistor filter branch L1 is grounded, and the third end of the first resistor filter branch L1 is connected to the third port P3 of the external circuit interface Z1.

[0042] The CANL end of the CAN transceiver U1 is connected to the first end of the second resistor filter branch L2 and the second port P2 of the external circuit interface Z1, the second end of the second resistor filter branch L2 is grounded, and the third end of the second resistor filter branch L2 is connected to the fourth port P4 of the external circuit interface Z1.

[0043] When the CANH terminal and the CANL terminal of the CAN transceiver U1 are connected to the terminal resistor, the third port P3 and the fourth port P4 of the external circuit interface Z1 are short-circuited.

[0044] For example, the CANH terminal of the CAN transceiver U1 is connected to the first port P1 via the high-level signal line CAN_H, and the CANL terminal is connected to the second port P2 via the low-level signal line CAN_L. The CANH and CANL terminals of the CAN transceiver U1 are differential signal ports for bidirectional transmission of differential signals. The CANH terminal is a high-level signal port that, in conjunction with the high-level signal line CAN_H, is used to transmit the high-level signal CANH signal. The CANL terminal is a low-level signal port that, in conjunction with the low-level signal line CAN_L, is used to transmit the low-level signal CANL signal.

[0045] Optionally, in this embodiment, the first resistor filter branch L1 is used to filter the CANH signal, and the second resistor filter branch L2 is used to filter the CANL signal. That is, two filter branches are used to filter the CANH signal and the CANL signal separately. At the same time, the external circuit interface Z1 is provided with four ports, wherein the first port P1 is connected to the first end of the first resistor filter branch L1, the second port P2 is connected to the first end of the second resistor filter branch L2, the third port P3 is connected to the third end of the first resistor filter branch L1, and the fourth port P4 is connected to the third end of the second resistor filter branch L2.

[0046] In this way, when the CAN communication circuit requires the connection of a terminal resistor based on the actual application environment and specific needs, that is, when the CANH and CANL terminals of the CAN transceiver U1 are connected to the terminal resistor, the third port P3 and the fourth port P4 are directly short-circuited, thereby short-circuiting the first resistor filter branch L1 and the second resistor filter branch L2. This allows the resistor in the first resistor filter branch L1 and the resistor in the second resistor filter branch L2 to be connected in series. In this way, the series-connected resistors in the first resistor filter branch L1 and the second resistor filter branch L2 serve as the terminal resistor connected to the CAN communication circuit, that is, between the CANH and CANL terminals of the CAN transceiver U1. At the same time, the first resistor filter branch L1 ensures filtering of the CANH signal, and the second resistor filter branch L2 ensures filtering of the CANL signal.

[0047] As can be seen from the foregoing, the external circuit interface Z1 is a plug-in terminal block with high vibration resistance. Connecting the third port P3 and the fourth port P4 via a connector can ensure the stability and reliability of the CAN communication circuit.

[0048] Optionally, when the CANH and CANL terminals of the CAN transceiver do not need to be connected to terminal resistors, the third port P3 and the fourth port P4 can be left empty, without affecting the filtering of the CANH signal by the first resistor filter branch L1 and the filtering of the CANL signal by the second resistor filter branch L2.

[0049] The CAN communication circuit provided in the embodiment of the present application is provided with a first resistor filter branch and a second resistor filter branch, which are used to filter the CANH signal and the CANL signal separately. When a terminal resistor needs to be connected between the CANH end and the CANL end of the CAN transceiver, the two resistor filter branches are short-circuited by short-circuiting the corresponding ports of the external circuit interface, so that the resistor in the first resistor filter branch and the resistor in the second resistor filter branch are connected in series between the two CAN signal lines and connected to the CAN communication circuit as a terminal resistor. In this way, the CAN communication circuit can be connected to the terminal resistor without changing the hardware structure of the CAN communication circuit, thereby unifying the hardware circuit of the CAN communication circuit and reducing the complexity of hardware management. In addition, since the external circuit interface is a plug-in terminal block, it has high vibration resistance, which ensures the stability and reliability of the CAN communication circuit and meets the requirements of small size and high vibration resistance.

[0050] In some embodiments, see Figure 2 The first resistance filter branch L1 includes a first resistor R1 and a first capacitor C1, and the second resistance filter branch L2 includes a second resistor R2 and a second capacitor C2.

[0051] The CANH terminal of the CAN transceiver U1 is connected to one end of the first resistor R1 and the first port P1 of the external circuit interface Z1. The other end of the first resistor R1 is connected to one end of the first capacitor C1 and the third port P3 of the external circuit interface Z1. The other end of the first capacitor C1 is grounded.

[0052] The CANL terminal of the CAN transceiver U1 is connected to one end of the second resistor R2 and the second port P2 of the external circuit interface Z1. The other end of the second resistor R2 is connected to one end of the second capacitor C2 and the fourth port P4 of the external circuit interface Z1. The other end of the second capacitor C2 is grounded.

[0053] One end of the first resistor R1 serves as the first end of the first resistance filter branch L1, the other end of the first capacitor C1 serves as the second end of the first resistance filter branch L1, and the other end of the first resistor R1 serves as the third end of the first resistance filter branch L1. One end of the second resistor R2 serves as the first end of the second resistance filter branch L2, the other end of the second capacitor C2 serves as the second end of the second resistance filter branch L2, and the other end of the second resistor R2 serves as the third end of the second resistance filter branch L2.

[0054] Exemplarily, the resistance filter branch in this embodiment can be an RC filter circuit, wherein the first resistor R1 and the first capacitor C1 are used to filter the CANH signal, and the second resistor R2 and the second capacitor C2 are used to filter the CANL signal, that is, a two-group resistor + capacitor structure is used to filter the CANH signal and the CANL signal separately.

[0055] When the CAN communication circuit requires the insertion of a terminal resistor based on the actual application environment and specific needs, that is, when a terminal resistor is required between the CANH and CANL terminals of the CAN transceiver U1, the third port P3 and the fourth port P4 are directly short-circuited to achieve the series connection of the first resistor R1 and the second resistor R2, and the parallel connection of the first capacitor C1 and the second capacitor C2. In this way, the series connection of the first resistor R1 and the second resistor R2 is connected to the CAN communication circuit as a terminal resistor, that is, between the CANH and CANL terminals of the CAN transceiver U1. At the same time, the first resistor R1 and the first capacitor C1 ensure filtering of the CANH signal, and the second resistor R2 and the second capacitor C2 ensure filtering of the CANL signal.

[0056] In this embodiment, a first resistor filter branch is provided to include a first resistor + a first capacitor, and a second resistor filter branch is provided to include a second resistor + a second capacitor, that is, two groups of "resistance + capacitor" structures are provided to filter the CANH signal and the CANL signal separately. When the CANH end and the CANL end of the CAN transceiver need to be connected to the terminal resistor, the above two groups of "resistance + capacitor" structures are short-circuited by short-circuiting the third port and the fourth port, so that the first resistor and the second resistor are connected between the two CAN signal lines and connected to the CAN communication circuit as the terminal resistor. In this way, the CAN communication circuit can be connected to the terminal resistor without changing the hardware structure of the CAN communication circuit.

[0057] In some embodiments, reference Figure 2 The CAN communication circuit further includes a common-mode inductor L. The CANH terminal of the CAN transceiver U1 is connected to a first input terminal of the common-mode inductor L, a first output terminal of the common-mode inductor L is connected to one end of the first resistor R1, a CANL terminal of the CAN transceiver U1 is connected to a second input terminal of the common-mode inductor L, and a second output terminal of the common-mode inductor L is connected to one end of the second resistor R2.

[0058] In this embodiment, the common-mode inductor L is provided to suppress the common-mode noise of the high-level signal line CAN_H and the low-level signal line CAN_L, thereby improving the anti-interference capability of the CAN communication circuit.

[0059] In some embodiments, reference Figure 2 The CAN communication circuit may further include: a first diode D1 and a second diode D2, and the first diode D1 and the second diode D2 are transient voltage suppression diodes (TVS diodes).

[0060] The cathode of the first diode D1 is connected to the first port P1 , the anode of the first diode D1 is grounded, the cathode of the second diode D2 is connected to the second port P2 , and the anode of the second diode D2 is grounded.

[0061] In this embodiment, the TVS diode is provided to improve the ability of the high-level signal line CAN_H and the low-level signal line CAN_L to resist shock pulses, protect the CAN communication circuit from the influence of transient voltage, and clamp the voltage within a safe range.

[0062] In some embodiments, the first resistor R1 and the second resistor R2 have the same resistance value, and the first capacitor C1 and the second capacitor C2 have the same capacitance value.

[0063] Here, the first resistor R1 and the second resistor R2 have the same resistance value, and the first capacitor C1 and the second capacitor C2 have the same capacitance value, which can achieve symmetrical filtering processing, improve filtering effects, and reduce the impact on the transmission characteristics of the differential signal. The resistance values ​​of the first resistor R1 and the second resistor R2, as well as the capacitance values ​​of the first capacitor C1 and the second capacitor C2, can be set according to the actual application scenario and requirements of the CAN communication circuit. For example, the resistance value of the first resistor R1 and the second resistor R2 can be 60.4 ohms (Ω), and the capacitance value of the first capacitor C1 and the second capacitor C2 can be 2.2 nanofarads (nF).

[0064] As can be seen from the foregoing, the CAN bus includes a high-level signal line CAN_H and a low-level signal line CAN_L. The first and second ends of the high-level signal line CAN_H are respectively connected to the CANH terminal and the first port P1. The third end of the high-level signal line CAN_H, located between the first and second ends, is connected to the first end of the first resistor filter branch L1, that is, connected to one end of the first resistor R1. Similarly, the first and second ends of the low-level signal line CAN_L are respectively connected to the CANL terminal and the second port P2. The third end of the low-level signal line CAN_L, located between the first and second ends, is connected to the first end of the second resistor filter branch L2, that is, connected to one end of the second resistor R2.

[0065] Optionally, the high-level signal line CAN_H and the low-level signal line CAN_L may be parallel and have the same length, which can improve the anti-interference capability and signal integrity of CAN communication.

[0066] Optional, see Figure 1 and Figure 2 The CAN transceiver also includes an RXD terminal and a TXD terminal. The RXD terminal is used to receive data, and the TXD terminal is used to transmit data. The RXD terminal is connected to the CAN controller, specifically to the RX terminal of the CAN controller, and the TXD terminal is connected to the CAN controller, specifically to the TX terminal of the CAN controller, to achieve data transmission between the CAN controller and the CAN transceiver, and further achieve data transmission between the CAN controller and the CAN bus.

[0067] For example, refer to Figure 1 and Figure 2,The CAN transceiver also includes a GND terminal and a VCC terminal. The GND terminal is grounded as a ground terminal, and the VCC terminal is connected to the power supply as a power terminal.

[0068] Optional, see Figure 1 and Figure 2 The CAN transceiver also includes an S terminal and an NC terminal. The S terminal is an enable control terminal used to control the CAN transceiver to be in working mode or sleep mode. The NC terminal is a digital IO level selection terminal used to select 5V or 3.3V level to communicate with a microcontroller unit (MCU) or a digital signal processor (DS).

[0069] An embodiment of the present application further provides a method for matching terminal resistances in a CAN communication circuit. The method is applicable to a CAN communication circuit and may include: when a terminal resistance is connected to the CANH and CANL terminals of a CAN transceiver, short-circuiting the third and fourth ports of an external circuit interface.

[0070] Wherein, the above-mentioned CAN communication circuit can be the CAN communication circuit provided by any embodiment of the present application. When the CAN communication circuit needs to be connected to a terminal resistor according to the actual application environment and specific needs, that is, when a terminal resistor needs to be connected between the CANH end and the CANL end of the CAN transceiver, the third port and the fourth port are directly short-circuited to achieve short-circuiting of the first resistor filter branch and the second resistor filter branch, so that the resistor in the first resistor filter branch and the resistor in the second resistor filter branch are connected in series. In this way, the resistor in the series-connected first resistor filter branch and the resistor in the second resistor filter branch are connected as terminal resistors to the CAN communication circuit, that is, between the CANH end and the CANL end of the CAN transceiver. At the same time, the first resistor filter branch and the second resistor filter branch ensure filtering of the CANH signal and the CANL signal.

[0071] Exemplarily, when the CANH and CANL terminals of the CAN transceiver are not connected to terminal resistors, the third port and the fourth port of the external circuit interface are empty, which does not affect the first resistor filter branch and the second resistor filter branch in filtering the CANH signal and the CANL signal.

[0072] The specific implementation process and principles of this embodiment can refer to the relevant description of the aforementioned embodiment and will not be repeated here.

[0073] An embodiment of the present application further provides a CAN communication system, which may include a CAN controller and a CAN communication circuit.

[0074] The CAN communication circuit may be any of the CAN communication circuits provided in any embodiment of the present application, and the CAN controller may be an MCU.

[0075] For example, in a CAN communication circuit, the RXD terminal of the CAN transceiver is connected to the CAN controller, and the TXD terminal of the CAN transceiver is connected to the CAN controller. Specifically, the RXD terminal of the CAN transceiver is connected to the RX terminal (data receiving pin) of the CAN controller, and the TXD terminal is connected to the TX terminal (data transmitting pin) of the CAN controller. The CAN controller transmits the data to be transmitted (logic level signal) to the TXD pin of the CAN transceiver via the TX terminal, and the CAN transceiver transmits the data (logic level signal) to the RX terminal of the CAN controller via the RXD terminal.

[0076] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0077] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application 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. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A CAN communication circuit, characterized in that: include: CAN transceiver, a first resistor filter branch, a second resistor filter branch and an external circuit interface; The external circuit interface is a plug-in terminal; The CANH end of the CAN transceiver is connected to the first end of the first resistor filter branch and the first port of the external circuit interface, the second end of the first resistor filter branch is grounded, and the third end of the first resistor filter branch is connected to the third port of the external circuit interface; The CANL terminal of the CAN transceiver is connected to the first end of the second resistor filter branch and the second port of the external circuit interface, the second end of the second resistor filter branch is grounded, and the third end of the second resistor filter branch is connected to the fourth port of the external circuit interface; When the CANH terminal and the CANL terminal of the CAN transceiver are connected to the terminal resistor, the third port and the fourth port of the external circuit interface are short-circuited.

2. The CAN communication circuit according to claim 1, characterized in that: The first resistance filter branch includes a first resistor and a first capacitor, and the second resistance filter branch includes a second resistor and a second capacitor; The CANH terminal of the CAN transceiver is connected to one end of the first resistor and the first port of the external circuit interface, the other end of the first resistor is connected to one end of the first capacitor and the third port of the external circuit interface; the other end of the first capacitor is grounded; The CANL end of the CAN transceiver is connected to one end of the second resistor and the second port of the external circuit interface, the other end of the second resistor is connected to one end of the second capacitor and the fourth port of the external circuit interface; the other end of the second capacitor is grounded.

3. The CAN communication circuit according to claim 1, characterized in that: When the CANH terminal and the CANL terminal of the CAN transceiver are not connected to the terminal resistor, the third port and the fourth port of the external circuit interface are empty.

4. The CAN communication circuit according to claim 2, characterized in that: The CAN communication circuit further includes: a common mode inductor; The CANH terminal of the CAN transceiver is connected to the first input terminal of the common-mode inductor, and the first output terminal of the common-mode inductor is connected to one end of the first resistor; The CANL terminal of the CAN transceiver is connected to the second input terminal of the common-mode inductor, and the second output terminal of the common-mode inductor is connected to one end of the second resistor.

5. The CAN communication circuit according to claim 2, characterized in that: The first resistor and the second resistor have the same resistance value, and the first capacitor and the second capacitor have the same capacitance value.

6. The CAN communication circuit according to any one of claims 1 to 5, characterized in that: The CANH terminal of the CAN transceiver is connected to the first port via a high-level signal line, and the CANL terminal of the CAN transceiver is connected to the second port via a low-level signal line.

7. The CAN communication circuit according to claim 6, characterized in that: The high-level signal line and the low-level signal line are parallel and have the same length.

8. A terminal resistance matching method for a CAN communication circuit, characterized in that: Applied to the CAN communication circuit according to any one of claims 1 to 7, the method comprises: When the terminal resistors are connected to the CANH and CANL terminals of the CAN transceiver, the third port and the fourth port of the external circuit interface are short-circuited.

9. The CAN communication circuit terminal resistance matching method according to claim 8, characterized in that: The method further comprises: When the CANH terminal and the CANL terminal of the CAN transceiver are not connected to the terminal resistor, the third port and the fourth port of the external circuit interface are empty.

10. A CAN communication system, characterized in that: The system comprises a CAN controller and a CAN communication circuit according to any one of claims 1 to 7.

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