CN114779697A - Isolation circuit for converting SPI (serial peripheral interface) to CAN (controller area network) bus - Google Patents

Abstract

The application discloses an isolation circuit for converting SPI to CAN bus, which is characterized in that the circuit comprises an isolation power module, a bus conversion module connected with the isolation power module and an electrostatic protection component connected with the bus conversion module; the isolation power supply module is used for isolating a first power supply and a second power supply; the bus conversion module is connected with the node controller and comprises an independent CAN protocol controller using a first power supply and a CAN bus repeater connected with the independent CAN protocol controller and the isolated power supply module; the electrostatic protection assembly comprises a common mode inductance module connected with the CAN bus transponder and a protection diode module connected with the common mode inductance module; the protection diode module is connected with an external CAN bus port. Can carry out power isolation and signal isolation with SPI commentaries on classics CAN bus circuit respectively to reduce the CAN communication trouble that outside electrostatic discharge caused, improve the interference killing feature of device. Compared with the existing isolation mode, the circuit has stronger anti-interference capability and simpler implementation mode.

Description

Isolation circuit for converting SPI (serial peripheral interface) to CAN (controller area network) bus

Technical Field

The application relates to the field of bus conversion, in particular to an isolation circuit for converting SPI into CAN bus.

Background

CAN is a short for Controller Area Network (Controller Area Network) and is one of the most widely used field buses internationally. With the increasing degree of industrial modernization, fieldbus technology plays an increasingly important role in the field of industrial control. However, in order to make the industrial control networking more flexible, a plurality of different buses are sometimes required in the same network, so that the conversion between different bus protocols becomes a key technology in the industrial control field. And SPI is an abbreviation for Serial Peripheral Interface (Serial Peripheral Interface). The SPI bus is a very extensive interface standard in embedded system application, and many device manufacturers use the standard, and in some embedded single-chip microcomputer application systems, on the premise that few pins are available, the conversion method of the SPI bus and the CAN bus is an economical and convenient interface expansion method. However, at present, the CAN is widely applied to industries such as new energy automobiles, rail transit, medical treatment, coal mines, motor driving and the like, and the electromagnetic environment of the industries is serious, so that how to resist interference is the most concerned topic of engineers.

Therefore, an isolation circuit for converting SPI to CAN bus is needed to effectively protect internal devices from external electrostatic discharge.

Disclosure of Invention

In order to solve the above problems, the present application provides an isolation circuit for converting SPI to CAN bus, including an isolation power module, a bus conversion module connected to the isolation power module, and an electrostatic protection component connected to the bus conversion module; the isolation power supply module is used for isolating a first power supply and a second power supply; the bus conversion module is connected with the node controller and comprises an independent CAN protocol controller using a first power supply and a CAN bus repeater connected with the independent CAN protocol controller and the isolation power supply module; the electrostatic protection assembly comprises a common mode inductance module connected with the CAN bus repeater and a protection diode module connected with the common mode inductance module; and the protection diode module is connected with an external CAN bus port.

In one example, the standalone CAN protocol controller employs a MCP2515 controller.

In one example, the MCP2515 controller outputs a CAN bus via a TXCAN interface and inputs a CAN bus via a RXCAN interface; the MCP2515 controller is connected with a first resistor and a first capacitor through a RESET interface.

In one example, the MCP2515 controller is connected to a clock crystal through an OSC1 interface and an OSC2 interface as a clock source for the MCP2515 controller.

In one example, the isolation power supply module is further provided with a decoupling capacitor submodule, the decoupling capacitor submodule at least comprises a first decoupling capacitor and a second decoupling capacitor, and the first decoupling capacitor and the second decoupling capacitor are connected with the ground wire in parallel.

In one example, the CAN bus repeater employs an ISO1050 plating isolated CAN repeater.

In one example, the isolated power module employs an RB-3305SHP converter.

In one example, a second resistor, a third resistor, a second capacitor, a third capacitor and a fourth capacitor are arranged between the independent CAN protocol controller and the CAN bus repeater, and the second resistor, the third resistor and the second capacitor are connected in parallel.

In one example, the common mode inductance module comprises a common mode inductance, a fourth resistance, a fifth resistance and a sixth resistance; the common mode inductor, the fourth resistor, the fifth resistor and the sixth resistor are connected in parallel.

In one example, the protection diode module is provided with a fifth capacitor, a sixth capacitor, a first protection diode and a second protection diode; the fifth capacitor, the sixth capacitor, the first protection diode and the second protection diode are connected in parallel; the isolation power supply module comprises a seventh capacitor, an eighth capacitor, a ninth capacitor and a tenth capacitor, wherein the seventh capacitor, the eighth capacitor, the ninth capacitor and the tenth capacitor are connected in parallel.

Through the SPI that this application provided changes CAN bus's isolating circuit CAN keep apart and the signal isolation SPI changes CAN bus circuit's power respectively to reduce the CAN communication trouble that outside electrostatic discharge caused effectively, improve the interference killing feature of inside device. Compared with the existing isolation mode, the circuit has stronger anti-interference capability and simpler implementation mode.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a schematic diagram of an isolation circuit for converting SPI to CAN bus in the embodiment of the present application;

FIG. 2 is a circuit diagram of an isolated power module according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram of a topology of an overall application of a CAN bus in an embodiment of the present application;

FIG. 4 is a schematic structural diagram of an ISO1050 in an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings. In the isolation, it is necessary to perform power isolation and signal isolation at the same time, thereby improving the isolation effect.

As shown in fig. 1 to fig. 4, an isolation circuit for converting SPI to CAN bus provided in the embodiments of the present application includes an isolation power module, a bus conversion module connected to the isolation power module, and an electrostatic protection component connected to the bus conversion module. The isolation power supply module is used for supplying power to the bus conversion module and the static protection component module. The isolation power module is used for isolating a first power supply and a second power supply, wherein in one embodiment, the first power supply is a P3V3 power supply, and the second power supply is a P5V power supply.

As shown in FIG. 2, in one embodiment, the isolation power supply module adopts RB-3305SHP converters, and RB-3305SHP series DC/DC converters are designed to isolate or convert DC power supply rails, have low cost, support isolation of 1KVDC/1s or 2KVDC/1s, have the working temperature ranging from-40 ℃ to +85 ℃, and support continuous short circuit protection. The P3V3 and GND CAN be converted into P5V _ CAN and GND _ CAN, and the two groups of signals are isolated independently.

The isolation power supply module isolates the P3V3 power supply from the voltage of a CAN bus, and the bus conversion module converts an SPI bus from a node controller into the CAN bus, and transmits the CAN bus to a J11 port after passing through the electrostatic protection assembly for interconnection of an external CAN bus.

The bus conversion module is connected with the node controller and comprises an independent CAN protocol controller using a first power supply and a CAN bus repeater connected with the independent CAN protocol controller and the isolation power supply module.

In one embodiment, the standalone CAN protocol controller employs a MCP2515 controller, the MCP2515 being a standalone CAN controller that fully supports the CAN V2.0B specification. The device is capable of sending and receiving standard and extended data frames as well as remote frames. The MCP2515 with two acceptance mask registers and six acceptance filter registers can filter out unwanted messages, thus reducing the overhead of a master single-chip Microcomputer (MCU). The connection between the MCP2515 and the MCU is implemented by a Serial Peripheral Interface (SPI) standard in the industry, which simplifies the application required to be connected to the CAN bus. In fig. 1, a PIN (13-16) of the MCP2515 controller is an SPI interface and is interconnected with a host side, a PIN (7-8) is a crystal input, and a PIN (1-2) is a CAN bus input/output PIN, and is interconnected with a post-stage ISO1050 CAN bus repeater after passing through an RC filter circuit.

As shown in fig. 3, in this embodiment, the overall application topology of the CAN bus is as follows: while the isolation power module isolates the P3V3 power supply from the CAN bus voltage, the SPI bus from the host (MCU, PSU, or related control node) passes through the MCP2515 chip, then passes through the ISO1050, namely the XCVR module, and is converted into the CAN bus, and then passes through the ESD protection to the J11 port for interconnection with the external CAN bus.

In one embodiment, a clock crystal is connected to the independent CAN protocol controller as a clock source of the independent CAN protocol controller. In fig. 1, the PIN (7-8) of the MCP2515 controller is externally attached to an 8MHz crystal that is used to provide the MCP2515 controller with a working reference clock crystal input.

In one embodiment, the isolated power supply module is further provided with a decoupling capacitor submodule comprising at least a first decoupling capacitor and a second decoupling capacitor. The decoupling capacitor is a capacitor arranged at a power supply end of an element in a circuit, can provide a relatively stable power supply, can reduce noise of the element coupled to the power supply end, and can indirectly reduce the influence of the noise of the element on other elements. The decoupling capacitor is also called decoupling capacitor, and is a filtering object for the interference of the output signal. The decoupling capacitor is used in the place where the amplifier circuit does not need to exchange current, and is used for eliminating self-excitation and making the amplifier stably work. In a circuit sharing a conductor, when a device needs to provide an output to the outside while sharing a power supply, the voltage of the conductor is simultaneously pulled down, and noise is generated and coupled into the shared circuit. In a noisy environment, these electromagnetic waves induce voltage signals in the conductors that affect the components in the loop. In a digital circuit, a device is likely to generate an erroneous signal due to disturbance at a critical position, thereby generating an erroneous operation. The decoupling capacitance can reduce the occurrence of the above situation. In fig. 1, the first decoupling capacitor and the second decoupling capacitor are C62 and C64, respectively.

As shown in fig. 4, in one embodiment, the CAN bus repeater employs an ISO1050 plating isolated CAN repeater. ISO1050 is a CAN repeater isolated by electroplating, a bus network with safety, stability and high reliability is constructed, each node and a cable must be isolated, so that various electrical noises, common-mode voltage, damage to systems and personnel caused by grounding loops and the like is avoided, and potential safety hazard faults are caused. The occupied PCB area is reduced, the design difficulty is reduced, and how to insert an isolating device between the controller and the transceiver for isolation is not needed to be considered. This transponder meets or is superior to the technical specifications of the ISO11898-2 standard. The device has several logic input and output buffers separated by silicon oxide insulated gates for use with an isolated power supply, and prevents noise currents on the data bus or other circuitry from entering local ground and interfering with and damaging sensitive circuitry.

The electrostatic protection assembly comprises a common-mode inductance module connected with the CAN bus transponder and a protection diode module connected with the common-mode inductance module, and the diode module is connected with an external CAN bus port. In fig. 1, the common mode inductor module is L10, and the protection diode module includes D8 and D9.

As shown in fig. 1, in one embodiment, the MCP2515 controller is connected to a first resistor R107 and a first capacitor C55 through a RESET interface. A second resistor R109, a third resistor R111, a second capacitor C290, a third capacitor C291 and a fourth capacitor C54 are arranged between the independent CAN protocol controller IC7 and the CAN bus repeater U107, and the second resistor R109, the third resistor R111 and the second capacitor C290 are connected in parallel. The common mode inductance module comprises a common mode inductance L10, a fourth resistor R112, a fifth resistor R108 and a sixth resistor R113; the common mode inductor L10, the fourth resistor R112, the fifth resistor R108 and the sixth resistor R113 are connected in parallel. The protection diode module is provided with a fifth capacitor C60, a sixth capacitor C61, a first protection diode D8 and a second protection diode D9; the fifth capacitor C60, the sixth capacitor C61, the first protection diode D8 and the second protection diode D9 are connected in parallel; the isolated power supply module comprises a seventh capacitor C344, an eighth capacitor C345, a ninth capacitor C342 and a tenth capacitor C343, wherein the seventh capacitor C344, the eighth capacitor C345, the ninth capacitor C342 and the tenth capacitor C343 are connected in parallel.

Therefore, after the circuit provided by the application is isolated from signals through a power supply, the CAN communication fault caused by external interference CAN be effectively reduced.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term "comprising", without further limitation, means that the element so defined is not excluded from the group consisting of additional identical elements in the process, method, article, or apparatus that comprises the element.

It will be understood by those skilled in the art that all or part of the steps in the method according to the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes instructions for executing the method according to the embodiments of the present invention. The storage medium described herein, such as: ROM/RAM, magnetic disks, optical disks, etc.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Finally, those skilled in the art to which the invention relates will readily appreciate that the conception and the specific embodiment disclosed may be readily utilized as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the spirit of the invention as defined by the appended claims.

Claims (10)

1. An isolation circuit for converting SPI into CAN bus is characterized in that the circuit comprises an isolation power module, a bus conversion module connected with the isolation power module, and an electrostatic protection component connected with the bus conversion module;

the isolation power supply module is used for isolating a first power supply and a second power supply;

the bus conversion module is connected with the node controller and comprises an independent CAN protocol controller using a first power supply and a CAN bus repeater connected with the independent CAN protocol controller and the isolation power supply module;

the electrostatic protection assembly comprises a common-mode inductance module connected with the CAN bus transponder and a protection diode module connected with the common-mode inductance module; and the protection diode module is connected with an external CAN bus port.

2. The circuit of claim 1 wherein the standalone CAN protocol controller employs a MCP2515 controller.

3. The circuit of claim 2, wherein the MCP2515 controller outputs a CAN bus via a TXCAN interface and inputs a CAN bus via a RXCAN interface;

the MCP2515 controller is connected with a first resistor and a first capacitor through a RESET interface.

4. The circuit of claim 2 wherein the MCP2515 controller has a clock crystal connected through an OSC1 interface and an OSC2 interface as a clock source for the MCP2515 controller.

5. The circuit of claim 1, wherein the isolated power supply module is further provided with a decoupling capacitor sub-module, the decoupling capacitor sub-module comprises at least a first decoupling capacitor and a second decoupling capacitor, and the first decoupling capacitor and the second decoupling capacitor are connected in parallel with a ground line.

6. The circuit of claim 1 wherein the CAN bus repeater employs an ISO1050 plated isolated CAN repeater.

7. The circuit of claim 1, wherein the isolated power supply module employs an RB-3305SHP converter.

8. The circuit of claim 1 wherein a second resistor, a third resistor, a second capacitor, a third capacitor, and a fourth capacitor are disposed between the independent CAN protocol controller and the CAN bus repeater, and wherein the second resistor, the third resistor, and the second capacitor are connected in parallel.

9. The circuit of claim 1, wherein the common mode inductance module comprises a common mode inductance, a fourth resistance, a fifth resistance, a sixth resistance; the common mode inductor, the fourth resistor, the fifth resistor and the sixth resistor are connected in parallel.

10. The circuit of claim 1, wherein the protection diode module is provided with a fifth capacitor, a sixth capacitor, a first protection diode, and a second protection diode; the fifth capacitor, the sixth capacitor, the first protection diode and the second protection diode are connected in parallel;

the isolation power supply module comprises a seventh capacitor, an eighth capacitor, a ninth capacitor and a tenth capacitor, wherein the seventh capacitor, the eighth capacitor, the ninth capacitor and the tenth capacitor are connected in parallel.

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