Disclosure of Invention
In view of the above, the embodiments of the present application provide a CAN communication circuit, a terminal resistor matching method, and a CAN communication system, so as to solve the technical problems of complex hardware management and increased management cost caused by the need of changing a hardware structure when the related technology matches the terminal resistor.
In a first aspect, the embodiment of the application provides a CAN communication circuit, which comprises a CAN transceiver, a first resistance filtering branch, a second resistance filtering branch and an external circuit interface, wherein the external circuit interface is a plug-in wiring terminal;
The CANH end of the CAN transceiver is connected with the first end of the first resistance filtering branch and the first port of the external circuit interface, the second end of the first resistance filtering branch is grounded, and the third end of the first resistance filtering branch is connected with the 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 a terminal resistor, the third port and the fourth port of the external circuit interface are short-circuited.
In a possible implementation manner of the first aspect, the first resistive filtering branch includes a first resistor and a first capacitor, and the second resistive filtering branch includes a second resistor and a second capacitor;
The CAN transceiver comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh capacitor and a fourth resistor, wherein the CANH end of the CAN transceiver is connected with one end of the first resistor and a first port of the external circuit interface, and the other end of the first resistor is connected with one end of the first capacitor and a third port of the external circuit interface;
The CANL end of the CAN transceiver is connected with one end of the second resistor and a second port of the external circuit interface, the other end of the second resistor is connected with one end of the second capacitor and a fourth port of the external circuit interface, and the other end of the second capacitor is grounded.
In a possible implementation manner of the first aspect, when the CANH end and the CANL end 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.
In a possible implementation manner of the first aspect, the CAN communication circuit further includes a common mode inductance;
the CANH end of the CAN transceiver is connected with the first input end of the common mode inductor, and the first output end of the common mode inductor is connected with one end of the first resistor;
And a CANL end of the CAN transceiver is connected with a second input end of the common mode inductor, and a second output end of the common mode inductor is connected with one end of the second resistor.
In a possible implementation manner of the first aspect, the resistances of the first resistor and the second resistor are the same, and the capacitance of the first capacitor and the second capacitor are the same.
In a possible implementation manner of the first aspect, the CANH end of the CAN transceiver is connected to the first port via a high level signal line, and the CANL end of the CAN transceiver is connected to the second port via a low level signal line.
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.
In a second aspect, an embodiment of the present application provides a CAN communication circuit termination resistance matching method, which is applied to the CAN communication circuit according to any one of the first aspect, and the method includes:
The third and fourth ports of the external circuit interface are shorted when CANH and CANL terminals of the CAN transceiver are connected to the termination resistor.
In a possible implementation manner of the second aspect, the method further includes:
And when the CANH end and the CANL end 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.
In a third aspect, an embodiment of the present application provides a CAN communication system, the system comprising a CAN controller and a CAN communication circuit according to any one of the first aspects.
It will be appreciated that the advantages of the second to third aspects may be found in the relevant description of the first aspect, and are not described in detail herein.
According to the CAN communication circuit, the terminal resistor matching method and the CAN communication system, the first resistor filtering branch and the second resistor filtering branch are arranged and used for separately filtering the CANH signal and the CANL signal, when the terminal resistor is needed to be accessed between the CANH end and the CANL end of the CAN transceiver, the two resistor filtering branches are short-circuited through corresponding ports of the short-circuited external circuit interface, the resistor in the first resistor filtering branch and the resistor in the second resistor filtering branch are connected between two CAN signal lines in series and are used as terminal resistors to be connected into the CAN communication circuit, and therefore the hardware structure of the CAN communication circuit is not changed, the CAN communication circuit CAN be connected into the terminal resistors, the hardware circuit of the CAN communication circuit is unified, the complexity of hardware management is reduced, and in addition, the external circuit interface is a plug-in type wiring terminal, the CAN communication circuit has high vibration resistance, the stability and reliability are guaranteed, and the requirements of small size and high vibration resistance are met.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Detailed Description
The present application will be more clearly described with reference to the following examples. The following examples will assist those skilled in the art in further understanding the function of the present application, but are not intended to limit the application in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present application.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
In the description of the present specification and the appended claims, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
Furthermore, references to "a plurality of" in embodiments of the present application should be interpreted as two or more.
In CAN communication, the termination resistor plays an important role, and CAN prevent signal reflection, improve anti-interference capability and the like. In general, whether the CAN communication circuit is accessed to the terminal resistor is determined according to the actual application scene and the specific requirement, and under different application scenes, in order to match whether the terminal resistor is accessed or not, the hardware structure of the CAN communication circuit needs to be changed, so that the hardware management is complex, the management cost is increased, and the hardware management is more complex especially when a plurality of CAN communication circuits exist.
In addition, the inventor researches and discovers that if the access terminal resistor is realized by adding the dial switch or the jumper cap, the dial switch is unstable and large in size, and the jumper cap has poor vibration resistance effect, and both the dial switch and the jumper cap CAN cause instability and poor reliability of the CAN communication circuit and influence the normal operation of the CAN communication circuit.
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 inventor researches and discovers that two resistance filtering branches CAN be respectively arranged for separately filtering CANH signals and CANL signals, and when an access terminal resistor is needed between the CANH end and the CANL end of the CAN transceiver, the two resistance filtering branches are short-circuited through the corresponding ports of the short-circuited external circuit interface, so that the resistors in the two resistance filtering branches are connected between two CAN signal lines in series, namely, the access terminal resistor of the CAN communication circuit is realized, thus the hardware circuit of the CAN communication circuit CAN be unified, and the complexity of hardware management is reduced.
Meanwhile, as a dial switch or a jumper wire cap is not required to be arranged, the stability and the reliability of the CAN communication circuit are ensured, and the requirements of small volume and high vibration resistance are met.
Fig. 1 is a schematic connection diagram of a CAN communication circuit according to an embodiment of the present application. As shown in fig. 1, the CAN communication circuit may include a CAN transceiver U1, a first resistance filtering branch L1, a second resistance filtering branch L2, and an external circuit interface Z1, where the external circuit interface Z1 is a pluggable connection terminal.
The CANH end of the CAN transceiver U1 is connected with the first end of the first resistance filtering branch L1 and the first port P1 of the external circuit interface Z1, the second end of the first resistance filtering branch L1 is grounded, and the third end of the first resistance filtering branch L1 is connected with the third port P3 of the external circuit interface Z1.
The CANL end of the CAN transceiver U1 is connected with the first end of the second resistance filtering branch L2 and the second port P2 of the external circuit interface Z1, the second end of the second resistance filtering branch L2 is grounded, and the third end of the second resistance filtering branch L2 is connected with the fourth port P4 of the external circuit interface Z1.
When CANH and CANL terminals of CAN transceiver U1 are connected to terminal resistors, third port P3 and fourth port P4 of external circuit interface Z1 are shorted.
Illustratively, the CANH end of CAN transceiver U1 is connected to first port P1 via high-level signal line can_h and the CANL end is connected to second port P2 via low-level signal line can_l. The CANH end and CANL end of the CAN transceiver U1 are differential signal ports for bi-directional transmission of differential signals. The CANH end is a high-level signal port, and is combined with a high-level signal line can_h for transmitting a high-level signal CANH signal, and the CANL end is a low-level signal port, and is combined with a low-level signal line can_l for transmitting a low-level signal CANL signal.
Optionally, in this embodiment, the first resistance filtering branch L1 is used to filter the CANH signal, and the second resistance filtering branch L2 is used to filter the CANL signal, that is, two paths of filtering branches are used to filter the CANH signal and the CANL signal separately. Meanwhile, the external circuit interface Z1 is provided with 4 ports, wherein the first port P1 is connected to the first end of the first resistance filtering branch L1, the second port P2 is connected to the first end of the second resistance filtering branch L2, the third port P3 is connected to the third end of the first resistance filtering branch L1, and the fourth port P4 is connected to the third end of the second resistance filtering branch L2.
Therefore, when the CAN communication circuit needs to be connected with the terminal resistor according to the practical application environment and specific requirements, namely the CANH end and the CANL end of the CAN transceiver U1 are connected with the terminal resistor, the third port P3 and the fourth port P4 are directly in short circuit, the short circuit of the first resistance filtering branch L1 and the second resistance filtering branch L2 is realized, the series connection of the resistor in the first resistance filtering branch L1 and the resistor in the second resistance filtering branch L2 is realized, and therefore the resistor in the first resistance filtering branch L1 and the resistor in the second resistance filtering branch L2 which are connected in series serve as the terminal resistor to be connected with the CAN communication circuit, namely the resistor is connected between the CANH end and the CANL end of the CAN transceiver U1. Meanwhile, the first resistance filtering branch L1 ensures the filtering of the CANH signal, and the second resistance filtering branch L2 ensures the filtering of the CANL signal.
From the foregoing, the external circuit interface Z1 is a pluggable connection terminal, which has high vibration resistance, and the stability and reliability of the CAN communication circuit CAN be ensured by connecting the third port P3 and the fourth port P4 in a connector manner.
Optionally, when the CANH end and the CANL end of the CAN transceiver do not need to be connected to the terminal resistor, the third port P3 and the fourth port P4 are empty, so that the filtering of the CANH signal by the first resistor filtering branch L1 is not affected, and the filtering of the CANL signal by the second resistor filtering branch L2 is not affected.
According to the CAN communication circuit provided by the embodiment of the application, the first resistance filtering branch and the second resistance filtering branch are arranged and used for separately filtering the CANH signal and the CANL signal, and when a terminal resistor is needed to be connected between the CANH end and the CANL end of the CAN transceiver, the two resistance filtering branches are short-circuited through corresponding ports of a short-circuited external circuit interface, so that the resistors in the first resistance filtering branch and the resistors in the second resistance filtering branch are connected in series between two CAN signal lines and are used as terminal resistors to be connected into the CAN communication circuit, thus the hardware structure of the CAN communication circuit is not changed, the CAN communication circuit CAN be connected into the terminal resistors, the hardware circuit of the CAN communication circuit is unified, the hardware management complexity is reduced, and in addition, the external circuit interface is a pluggable wiring terminal, the stability and the reliability of the CAN communication circuit are ensured, and the requirements of small volume and high vibration resistance are met.
In some embodiments, referring to fig. 2, the first resistive filtering branch L1 includes a first resistor R1 and a first capacitor C1, and the second resistive filtering branch L2 includes a second resistor R2 and a second capacitor C2.
The CANH end of the CAN transceiver U1 is connected with one end of a first resistor R1 and a first port P1 of an external circuit interface Z1, the other end of the first resistor R1 is connected with one end of a first capacitor C1 and a third port P3 of the external circuit interface Z1, and the other end of the first capacitor C1 is grounded.
The CANL end of the CAN transceiver U1 is connected with one end of a second resistor R2 and a second port P2 of the external circuit interface Z1, the other end of the second resistor R2 is connected with one end of a second capacitor C2 and a fourth port P4 of the external circuit interface Z1, and the other end of the second capacitor C2 is grounded.
One end of the first resistor R1 is used as a first end of the first resistor filtering branch L1, the other end of the first capacitor C1 is used as a second end of the first resistor filtering branch L1, and the other end of the first resistor R1 is used as a third end of the first resistor filtering branch L1. One end of the second resistor R2 is used as a first end of the second resistor filtering branch L2, the other end of the second capacitor C2 is used as a second end of the second resistor filtering branch L2, and the other end of the second resistor R2 is used as a third end of the second resistor filtering branch L2.
For example, the resistive filter branch in this embodiment may be an RC filter circuit, where 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 structure of two sets of resistors and capacitors is used to filter the CANH signal and the CANL signal separately.
When the CAN communication circuit needs to be connected into a terminal resistor according to the practical application environment and specific requirements, namely the terminal resistor is needed to be connected between the CANH end and the CANL end of the CAN transceiver U1, the third port P3 and the fourth port P4 are directly short-circuited, 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 are realized, and therefore the first resistor R1 and the second resistor R2 which are connected in series serve as the terminal resistor to be connected into the CAN communication circuit, namely the terminal resistor is connected between the CANH end and the CANL end of the CAN transceiver U1. Meanwhile, the first resistor R1 and the first capacitor C1 ensure the filtering of the CANH signal, and the second resistor R2 and the second capacitor C2 ensure the filtering of the CANL signal.
In this embodiment, the first resistor filtering branch includes a first resistor+a first capacitor, and the second resistor filtering branch includes a second resistor+a second capacitor, that is, two sets of "resistor+capacitor" structures are set, so as to separately filter the CANH signal and the CANL signal, and when the CANH end and the CANL end of the CAN transceiver need to be connected to the terminal resistor, the third port and the fourth port are short-circuited, so that the two sets of "resistor+capacitor" structures are short-circuited, the first resistor and the second resistor are connected between the two CAN signal lines, and the first resistor and the second resistor are connected to the CAN communication circuit as the terminal resistor, so that the hardware structure of the CAN communication circuit is not changed, and the CAN communication circuit CAN be connected to the terminal resistor.
In some embodiments, referring to FIG. 2, the CAN communication circuit further includes a common mode inductance L. The CANH end of the CAN transceiver U1 is connected with the first input end of the common-mode inductor L, the first output end of the common-mode inductor L is connected with one end of the first resistor R1, the CANL end of the CAN transceiver U1 is connected with the second input end of the common-mode inductor L, and the second output end of the common-mode inductor L is connected with one end of the second resistor R2.
The common mode inductance L is arranged in the embodiment, so that common mode noise of the high-level signal line CAN_H and the low-level signal line CAN_L CAN be restrained, and the anti-interference capability of the CAN communication circuit is improved.
In some embodiments, referring to FIG. 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 (TRANSIENT VOLTAGE SUPPRESSION DIODE, TVS diodes).
The negative pole of first diode D1 is connected first port P1, and the positive pole of first diode D1 is ground connection, and the second port P2 is connected to the negative pole of second diode D2, and the positive pole of second diode D2 is ground connection.
The TVS diode is arranged in the embodiment, so that the capability of the high-level signal line CAN_H and the low-level signal line CAN_L for resisting impact pulses CAN be improved, the CAN communication circuit is protected from being influenced by instantaneous voltage, and the voltage is clamped in a safety range.
In some embodiments, the first resistor R1 and the second resistor R2 have the same resistance, and the first capacitor C1 and the second capacitor C2 have the same capacitance.
Here, the resistances of the first resistor R1 and the second resistor R2 are the same, and the capacitances of the first capacitor C1 and the second capacitor C2 are the same, so that symmetrical filtering processing can be realized, the filtering effect can be improved, and the influence on the transmission characteristics of the differential signal can be reduced. The resistance values of the first resistor R1 and the second resistor R2, and the capacitance values of the first capacitor C1 and the second capacitor C2 may be set according to the actual application scenario and the requirement of the CAN communication circuit, for example, the resistance values of the first resistor R1 and the second resistor R2 may be 60.4 ohms (Ω), and the capacitance values of the first capacitor C1 and the second capacitor C2 may be 2.2 nano-meters (nF).
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 end and the second end of the high-level signal line can_h are respectively connected to the CANH end and the first port P1, and the third end, located between the first end and the second end, of the high-level signal line can_h is connected to the first end of the first resistor filtering branch L1, that is, to one end of the first resistor R1. Similarly, the first end and the second end of the low-level signal line can_l are connected to the CANL end and the second port P2, respectively, and the third end of the low-level signal line can_l located between the first end and the second end thereof is connected to the first end of the second resistance filtering branch L2, that is, to one end of the second resistance R2.
Alternatively, the high-level signal line can_h and the low-level signal line can_l may be parallel and have the same length, so that the anti-interference capability and signal integrity of CAN communication CAN be improved.
Optionally, referring to fig. 1 and 2, the can transceiver further includes an RXD end and a TXD end, where the RXD end is a data receiving end and the TXD end is a data transmitting end. The RXD end is connected with the CAN controller, the RX end of the CAN controller is specifically connected, the TXD end is connected with the CAN controller, and the TX end of the CAN controller is specifically connected, so that data transmission between the CAN controller and the CAN transceiver is realized, and further data transmission between the CAN controller and the CAN bus is realized.
Illustratively, referring to fig. 1 and 2, the can transceiver further includes a GND terminal as a ground terminal and a VCC terminal as a power terminal connected to a power source.
Optionally, referring to fig. 1 and 2, the CAN transceiver further includes an S terminal, which is an enable control terminal, for controlling the CAN transceiver to be in an operation mode or a sleep mode, and an NC terminal, which is a digital IO level selection terminal, for selecting a 5V or 3.3V level to communicate with a microcontroller (Microcontroller Unit, MCU) or a digital signal Processor (DIGITAL SIGNAL Processor, DS).
The embodiment of the application also provides a CAN communication circuit terminal resistor matching method. The method is applicable to a CAN communication circuit and CAN comprise the step of shorting a third port and a fourth port of an external circuit interface when a CANH end and a CANL end of a CAN transceiver are connected to a terminal resistor.
The CAN communication circuit CAN be any CAN communication circuit provided by the embodiment of the application. When the CAN communication circuit needs to be connected into a terminal resistor according to the practical application environment and specific requirements, namely the terminal resistor is needed to be connected between the CANH end and the CANL end of the CAN transceiver, the third port and the fourth port are directly in short circuit, the short circuit of the first resistance filtering branch and the second resistance filtering branch is realized, the series connection of the resistor in the first resistance filtering branch and the resistor in the second resistance filtering branch is realized, and therefore the resistor in the first resistance filtering branch and the resistor in the second resistance filtering branch which are connected in series serve as the terminal resistor to be connected into the CAN communication circuit, namely the terminal resistor is connected between the CANH end and the CANL end of the CAN transceiver. Meanwhile, the first resistance filtering branch and the second resistance filtering branch ensure the filtering of CANH signals and CANL signals.
Illustratively, when the CANH end and the CANL end 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, and the first resistance filtering branch and the second resistance filtering branch are not affected to filter the CANH signal and the CANL signal.
The specific implementation process and principle of this embodiment may refer to the related description of the foregoing embodiment, which is not repeated herein.
An embodiment of the present application further provides a CAN communication system, where the CAN communication system may include a CAN controller and a CAN communication circuit.
The CAN communication circuit CAN be any CAN communication circuit provided by the embodiment of the application. The CAN controller may be an MCU.
Illustratively, an RXD end of a CAN transceiver in the CAN communication circuit is connected with the CAN controller, and a TXD end of the CAN transceiver is connected with the CAN controller. Specifically, the RXD end of the CAN transceiver is connected to the RX end (data receiving pin) of the CAN controller, and the TXD end is connected to the TX end (data transmitting pin) of the CAN controller. The CAN controller transmits data (logic level signals) to be transmitted to a TXD pin of the CAN transceiver through a TX end, and the CAN transceiver transmits data (logic level signals) to an RX end of the CAN controller through an RXD end.
It should be understood that the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic, and should not limit the implementation process of the embodiment of the present application.
The foregoing embodiments are merely illustrative of the technical solutions of the present application, and not restrictive, and although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that modifications may still be made to the technical solutions described in the foregoing embodiments or equivalent substitutions of some technical features thereof, and that such modifications or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.