Multipath CAN redundancy and relay circuit, system and communication method based on domestic FPGA

Abstract

The invention relates to the field of electronic devices, in particular to a multi-channel CAN redundancy and relay circuit and system based on a domestic FPGA and a communication method. The circuit comprises an FPGA, an optocoupler, a CAN transceiver, a protection circuit and a connector, the output end of the FPGA is connected with the input end of the CAN transceiver through the optocoupler, and the output end of the CAN transceiver is connected with the connector through the protection circuit; the protection circuit comprises a common-mode inductor, a lightning protection tube, a transient suppression diode, a gas discharge tube and a shielded twisted pair, the lightning protection tube serves as pre-stage protection and bears most surge energy firstly, the transient suppression diode performs fine clamping, and the common-mode inductor further filters residual common-mode noise. Through collaborative design of software and hardware, redundant backup, intelligent relay and full localization are integrated, reliability, distance and expansibility of CAN communication in a complex transmission environment are realized, and an excellent solution is provided for constructing a high-reliability and wide-coverage industrial communication network.

Description

Technical Field

[0001] This invention relates to the field of electronic devices, specifically to a multi-channel CAN redundancy and relay circuit, system, and communication method based on a domestically produced FPGA. Background Technology

[0002] With the rapid development of industrial automation, automotive electronics, intelligent transportation, and aerospace, Controller Area Network (CAN) bus has become one of the core technologies for data communication between devices due to its high reliability, real-time performance, and low cost. However, as modern systems evolve towards larger scale, greater complexity, and greater distribution, the traditional single-channel CAN bus architecture has gradually revealed bottlenecks in communication reliability, transmission distance, and node expansion capabilities, making it difficult to meet the stringent requirements of critical fields for "zero interruption" and "wide coverage" communication systems.

[0003] First, regarding communication reliability, traditional single-channel CAN buses are susceptible to single-point-of-failure risks. In automotive electronics, critical subsystems such as powertrains and chassis control rely on the CAN bus for data exchange between ECUs (Electronic Control Units). If the bus line is interrupted due to mechanical wear, electromagnetic interference, or short circuit, it will directly lead to vehicle control failure and cause safety accidents. In industrial control scenarios, sensors, actuators, and controllers on the production line are connected via the CAN bus. A single-channel bus failure can cause the entire production line to shut down, resulting in significant economic losses. Furthermore, while the CAN bus's arbitration mechanism can resolve node contention issues, problems such as data frame loss and increased error frames remain prominent when the bus load rate is too high or encounters strong electromagnetic interference. Traditional architectures lack effective fault isolation and self-healing capabilities.

[0004] Currently, existing solutions have significant limitations. Regarding reliability, some scenarios employ dual-channel CAN bus redundancy designs, but these are mostly simple "hot standby" modes, lacking rapid detection and switching mechanisms for bus faults. Switching delays can lead to data loss. Regarding transmission distance, while CAN repeaters can extend communication distance, traditional repeaters can only amplify and forward single-channel signals, lacking redundancy backup capabilities. They themselves become new single points of failure, and cascading multiple repeaters can easily lead to accumulated signal delays and timing disruptions, affecting the real-time performance of the entire system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a multi-channel CAN redundancy and relay circuit, system, and communication method based on a domestically produced FPGA, which is used to improve the reliability of CAN networks.

[0006] To solve the aforementioned technical problem, the present invention adopts the following technical solution: a CAN redundancy and relay circuit based on a domestically produced FPGA, comprising an FPGA, an optocoupler, a CAN transceiver, a protection circuit, and a connector. The output of the FPGA is connected to the input of the CAN transceiver via the optocoupler, and the output of the CAN transceiver is connected to the connector via the protection circuit. The FPGA outputs a TTL level signal to drive the CAN transceiver to transmit and receive CAN communication signals. The protection circuit includes a common-mode inductor L1, a surge protector, a transient suppression diode D3, a gas discharge tube, and a shielded twisted-pair cable. The common-mode inductor L1 is connected between the CAN transceiver and the connector. The surge protector and the transient suppression diode D3 are connected in series between the positive and negative output terminals of the CAN transceiver. The gas discharge tube is connected between the positive and negative output terminals of the CAN transceiver, and its common electrode is grounded. The shielded twisted-pair cable is connected between the grounding terminal of the CAN transceiver and the grounding terminal of the connector, and the common electrode of the shielded twisted-pair cable and the gas discharge tube is grounded at the same point.

[0007] Furthermore, pin 1 of common mode inductor L1 is connected to the positive terminal of the CAN transceiver output, pin 2 of common mode inductor L1 is connected to the positive terminal of the connector, pin 3 of common mode inductor L1 is connected to the negative terminal of the connector, and pin 4 of common mode inductor L1 is connected to the negative terminal of the CAN transceiver output.

[0008] Furthermore, the surge protector includes diodes D1 and D2 connected in reverse parallel. The anode of diode D1 is connected to the positive terminal of the CAN transceiver output, and the cathode of diode D1 is connected to one end of transient suppression diode D3. The cathode of diode D2 is connected to the positive terminal of the CAN transceiver output, and the anode of diode D2 is connected to one end of transient suppression diode D3. The other end of transient suppression diode D3 is connected to the negative terminal of the CAN transceiver output.

[0009] Furthermore, an RC filter circuit is provided between the shielded twisted pair cable and the ground terminal of the CAN transceiver.

[0010] Furthermore, the FPGA's ground terminal is connected to the CAN transceiver's ground terminal and grounded at the same point. The FPGA's power supply terminal is connected to the CAN transceiver's power supply terminal and connected to power supply EP1. A filter capacitor is provided between the ground connection line and the power connection line.

[0011] This invention also discloses a CAN redundancy and relay system based on a domestically produced FPGA, including a CAN bus, CAN nodes, CAN channels, and a data processing module. CAN nodes are set on the CAN bus, and multiple CAN nodes are connected through CAN channels. The CAN channels adopt the circuit described above. The data processing module is connected to the CAN nodes and is used to selectively forward the data received by the CAN nodes. Each CAN node is connected to two redundant CAN channels as input channels, and each CAN node is connected to two redundant CAN channels as output channels. This system realizes single-channel bidirectional or two-channel bidirectional data reception and forwarding functions.

[0012] Furthermore, the baud rate and data format of the CAN channel can be set via the FPGA, and the baud rates of the CAN nodes at both ends of the CAN channel can be the same or different.

[0013] This invention also discloses a communication method, which is based on the above-mentioned system and includes the following steps: S01, the CAN node receives the data frame from the input channel and sends the data frame to the data processing module; S02. The data processing module parses the ID in the data frame. If the ID matches the local machine, the received data frame is a local data packet, which is then transmitted to the SOC of this node. If the ID does not match the local machine, then proceed to step S03. S03. Further parse the data frame to determine whether the data frame needs to be forwarded and the address of the target device for forwarding. If the data frame needs to be forwarded, proceed to step S04. If the data frame does not need to be forwarded, discard it or process it in this CAN node. S04. Perform electromagnetic interference removal and square wave shaping on the data frames that need to be forwarded to obtain reassembled data frames and send them back to the CAN bus.

[0014] Furthermore, in step S03, the parsing of the data frame includes: Frame type extraction: The frame type is identified based on the frame header of the data frame. If it is a data frame, it is determined whether it needs to be forwarded. If it is a remote frame, the target device is matched according to the request data. If it is an error frame, it is discarded. If it is an overload frame, it is also discarded. Frame ID extraction: Extract the identifier ID of the data frame and determine the target device of the remote frame based on the ID; Error status determination is achieved by parsing the CRC checksum and ACK bit of the data frame to determine whether it is an error frame; Filtering and forwarding: In the CAN bus data link layer, an independent subnet is divided, key information of the CAN frame is parsed, and a decision is made on whether to forward the frame according to preset filtering rules.

[0015] Furthermore, in step S04, electromagnetic interference mixed in during transmission is eliminated by using a low-pass filter and a differential signal comparator, and the attenuated distorted waveform is restored to a standard square wave conforming to the CAN specification. The rise / fall time of the standard square wave is ≤10% of the bit period.

[0016] The beneficial effects of this invention are as follows: This invention achieves automatic fault detection and millisecond-level rapid switching by using a four-channel redundancy design (two input redundancies and two output redundancies) combined with an intelligent fault detection algorithm. When the primary channel (e.g., CAN1) fails, the system can seamlessly and quickly switch to the backup channel (CAN2), ensuring "zero interruption" of the communication link. This completely solves the risk of single-point failures caused by line interruptions, electromagnetic interference, etc., meeting the high reliability requirements of communication systems in key fields such as industrial automation, automotive electronics, and aerospace. Utilizing the programmable hardware and software features of domestically produced FPGAs brings extremely high flexibility. The data flow direction of the CAN channel (e.g., CAN1->CAN3 or bidirectional forwarding), communication baud rate, frame filtering rules (based on frame ID), etc., can all be flexibly configured through software without modifying the hardware. With the rich I / O resources and parallel processing capabilities of FPGAs, redundancy and relay of up to 20 CAN communication links can be easily expanded, far exceeding the expansion limitations of traditional dedicated relay chips, making it very suitable for large-scale distributed control systems. The data link layer performs deep analysis and intelligent regeneration of CAN frames. By identifying frame type, extracting ID, and performing CRC checks, erroneous frames and redundant data can be accurately filtered, preventing them from consuming bandwidth and spreading faults, thus achieving "on-demand communication" between subnets. Data to be forwarded is processed by a built-in low-pass filter and differential comparator, effectively eliminating interference and restoring attenuated and distorted waveforms to standard square waves conforming to CAN specifications, ensuring stable dominant / recessive voltage values. This fundamentally solves the problems of signal attenuation, timing disorder, and reduced anti-interference capability caused by excessive transmission distance and too many nodes, greatly extending the effective communication distance and ensuring data integrity. The hardware integrates multiple protection circuits, including high-speed optocoupler isolation, TVS diodes, common-mode inductors, and surge protectors, forming a hierarchical protection mechanism. This design effectively resists electrical threats in harsh environments such as lightning surges, common-mode interference, and ground potential differences, significantly improving the system's survivability and long-term operational stability in harsh industrial environments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the circuit described in Example 1; Figure 2 This is a block diagram of the system described in Example 2. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 This embodiment discloses a multi-channel CAN redundancy and relay circuit based on a domestically produced FPGA, such as... Figure 1 As shown, the system includes an FPGA, an optocoupler, a CAN transceiver, a protection circuit, and a connector. The FPGA output is connected to the CAN transceiver input via the optocoupler, and the CAN transceiver output is connected to the connector via the protection circuit. The FPGA outputs a TTL level signal to drive the CAN transceiver to transmit and receive CAN communication signals. The protection circuit includes a common-mode inductor L1, a surge protector, a transient voltage suppressor diode D3, a gas discharge tube GDT, and a shielded twisted-pair cable. The common-mode inductor L1 is connected between the CAN transceiver and the connector. Pin 1 of the common-mode inductor L1 is connected to the positive terminal CANH of the CAN transceiver output, pin 2 of the common-mode inductor L1 is connected to the positive terminal 1H of the connector, pin 3 of the common-mode inductor L1 is connected to the negative terminal 2L of the connector, and pin 4 of the common-mode inductor L1 is connected to the negative terminal CANL of the CAN transceiver output. A surge protector and transient voltage suppressor diode D3 are connected in series between the positive output terminal CANH and the negative output terminal CANL of the CAN transceiver. A gas discharge tube (GDT) is connected between the positive output terminal CANH and the negative output terminal CANL of the CAN transceiver, with its common electrode grounded. A shielded twisted pair cable is connected between the ground terminal CANG of the CAN transceiver and the ground terminal of the connector, and an RC filter circuit is provided between the shielded twisted pair cable and the ground terminal of the CAN transceiver. The common electrode of the shielded twisted pair cable and the gas discharge tube GDT is grounded through the same point.

[0020] In this embodiment, the surge protector consists of diodes D1 and D2 connected in reverse parallel. The anode of diode D1 is connected to the positive terminal CANH of the CAN transceiver output, and the cathode of diode D1 is connected to one end of transient suppression diode D3. The cathode of diode D2 is connected to the positive terminal CANH of the CAN transceiver output, and the anode of diode D2 is connected to one end of transient suppression diode D3. The other end of transient suppression diode D3 is connected to the negative terminal of the CAN transceiver output.

[0021] The FPGA's ground terminal GND is connected to the CAN transceiver's ground terminal GND and grounded through the same point. The FPGA's power supply terminal VCC is connected to the CAN transceiver's power supply terminal VCC and connected to power supply EP1. A filter capacitor is provided between the ground connection line and the power connection line.

[0022] In this embodiment, the FPGA uses Fudan Microelectronics FMQL45T900 to implement the embedded operating system and control the corresponding pins to output TTL levels, thereby driving the subsequent CAN transceiver (Shenzhen Guowei SM1050) to transmit and receive CAN communication signals. Multiple protection circuits are applied to the CAN link to ensure normal operation in harsh environments (such as lightning strikes and electromagnetic interference). The UART function, implemented entirely by the FPGA's internal programmable logic resources, allows for flexible configuration of baud rate and data format, without relying on hard core resources. The UART-to-CAN signal uses a high-speed optocoupler for isolation, blocking ground potential difference, common-mode interference, and fault current transmission. Electrical signals are transmitted via optical transmission to achieve a high-speed communication scheme with electrical isolation, ensuring both electrical isolation safety and meeting the real-time requirements of CAN communication. External protection measures such as TVS diodes, common-mode inductors, surge protectors, shielded twisted-pair cables, or single-point grounding on the same network are added to the CANH / CANL terminals. Surge protectors act as the initial protection stage, absorbing most of the surge energy. TVS diodes provide fine clamping, while common-mode inductors further filter out residual common-mode noise. TVS diodes, common-mode inductors, surge protectors, shielded twisted-pair cables, or single-point grounding protection on the same network all enhance the anti-interference capability and stability of the CAN bus, protecting it from various electrical interferences and transient overvoltages. Employing a fully domestically produced solution, core chips (FPGA, CAN transceiver), operating system (Lingjiu Embedded Real-Time Operating System (SightOS)), and key algorithms (communication protocols, control logic) are all developed by a domestic team, achieving core self-development and full compatibility.

[0023] Example 2 This embodiment discloses a CAN redundancy and relay system based on a domestically produced FPGA, such as... Figure 2 As shown, the system includes a CAN bus, CAN nodes, CAN channels, and a data processing module. CAN nodes are mounted on the CAN bus, and multiple CAN nodes are connected via CAN channels. The CAN channels use the circuit described in Example 1. The data processing module is connected to the CAN nodes and is used to selectively forward the data received by the CAN nodes. Each CAN node is connected to two redundant CAN channels as input channels, and each CAN node is connected to two redundant CAN channels as output channels. This system enables single-channel bidirectional or two-channel bidirectional data reception and forwarding functions.

[0024] In this embodiment, the baud rate and data format of the CAN channel are set via FPGA, and the baud rates of the CAN nodes at both ends of the CAN channel may be the same or different.

[0025] This embodiment sets up CAN1 and CAN2 for redundancy, deploying two independent CAN buses (CAN1 as the primary bus and CAN2 as the backup bus). In the event of a primary bus failure, the system automatically switches to the backup bus, or the two buses operate in parallel, ensuring a highly reliable design with uninterrupted communication and no data loss. Its core mechanism revolves around four key aspects: fault detection, bus switching, data synchronization, and redundancy management, mitigating the "single point of failure" risk inherent in a single bus.

[0026] The CAN data flow is controllable, enabling CAN1->CAN3, CAN3->CAN1, or bidirectional data reception and forwarding between two channels. It supports CAN2.0A and CAN2.0B protocols, and standard and extended frame formats. The two channels can be configured with different baud rates, and it also supports simultaneous connection to two CAN networks with different baud rates, enabling CAN repeater functionality.

[0027] Example 3 This embodiment discloses a communication method, which is implemented based on the system of Embodiment 2, and includes the following steps: S01, the CAN node receives the data frame from the input channel and sends the data frame to the data processing module; S02. The data processing module parses the ID in the data frame. If the ID matches the local machine, the received data frame is a local data packet, which will be transmitted to the SOC with ARM core for further processing and response through the internal AXI bus. If the ID does not match the local machine, proceed to step S03. S03. Further parse the data frame to determine whether the data frame needs to be forwarded and the address of the target device for forwarding. If the data frame needs to be forwarded, proceed to step S04. If the data frame does not need to be forwarded, discard it or process it in this CAN node. S04. Perform electromagnetic interference removal and square wave shaping on the data frames that need to be forwarded to obtain reassembled data frames and send them back to the CAN bus.

[0028] Step S03, the parsing of the data frame includes: Frame type extraction: The frame type is identified based on the frame header of the data frame. If it is a data frame, it is determined whether it needs to be forwarded. If it is a remote frame, the target device is matched according to the request data. If it is an error frame, it is discarded. If it is an overload frame, it is also discarded and not forwarded.

[0029] Frame ID extraction: Extract the identifier ID of the data frame (11 bits for standard frames and 29 bits for extended frames). Determine the target device of the data frame based on the ID. For example, the preset ID range of target device A is 0x000~0x1FF, and the ID range of target device B is 0x200~0x3FF.

[0030] Error status is determined by parsing the CRC checksum and ACK bit of the data frame to determine whether it is an error frame; error frames are discarded directly and do not enter the forwarding process.

[0031] Filtering and forwarding: In the CAN bus data link layer, independent subnets are divided, key information of CAN frames is parsed, and whether a frame is to be forwarded is determined according to preset filtering rules. This avoids redundant data occupying bandwidth, realizes "on-demand communication" between devices, and enables selective data forwarding between subnets, while isolating faulty and redundant data.

[0032] In step S04, electromagnetic interference (such as motor noise and high-voltage pulses in industrial environments) mixed in during transmission is eliminated by a low-pass filter and a differential signal comparator. The attenuated distorted waveform (such as a slowed rise time and insufficient peak voltage) is repaired into a standard square wave conforming to the CAN specification (ensuring that the rise / fall time is ≤10% of the bit period to meet the requirements of high-speed transmission). Regardless of how much the original input signal is attenuated, the regenerated "dominant level" strictly maintains a 2V differential voltage, and the "recessive level" maintains 0V. The signal is sent back to the CAN bus to ensure that the data frame output to the downstream node can be accurately identified, thus solving problems such as signal attenuation, transmission delay, and decreased interference immunity caused by excessive physical distance and too many nodes on the bus.

[0033] Leveraging the real-time capabilities and rich I / O scalability of FPGAs, up to 20-channel CAN redundancy + relay designs can be implemented.

[0034] The above description is merely the basic principle and preferred embodiment of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention are within the scope of protection of the present invention.

Claims

1. A CAN redundancy and relay circuit based on a domestically produced FPGA, characterized in that: The system includes an FPGA, an optocoupler, a CAN transceiver, a protection circuit, and a connector. The FPGA output is connected to the CAN transceiver input via the optocoupler, and the CAN transceiver output is connected to the connector via the protection circuit. The FPGA outputs a TTL level signal to drive the CAN transceiver to transmit and receive CAN communication signals. The protection circuit includes a common-mode inductor L1, a surge protector, a transient voltage suppressor diode D3, a gas discharge tube, and a shielded twisted-pair cable. The common-mode inductor L1 is connected between the CAN transceiver and the connector. The surge protector and transient voltage suppressor diode D3 are connected in series between the positive and negative terminals of the CAN transceiver output. The gas discharge tube is connected between the positive and negative terminals of the CAN transceiver output, and its common electrode is grounded. The shielded twisted-pair cable is connected between the grounding terminal of the CAN transceiver and the grounding terminal of the connector. The common electrode of the shielded twisted-pair cable and the gas discharge tube is grounded at the same point.

2. The CAN redundancy and relay circuit based on domestically produced FPGA according to claim 1, characterized in that: Pin 1 of common mode inductor L1 is connected to the positive terminal of the CAN transceiver output, pin 2 of common mode inductor L1 is connected to the positive terminal of the connector, pin 3 of common mode inductor L1 is connected to the negative terminal of the connector, and pin 4 of common mode inductor L1 is connected to the negative terminal of the CAN transceiver output.

3. The CAN redundancy and relay circuit based on domestic FPGA according to claim 1, characterized in that: The surge protector includes diodes D1 and D2 connected in reverse parallel. The anode of diode D1 is connected to the positive terminal of the CAN transceiver output, and the cathode of diode D1 is connected to one end of transient suppression diode D3. The cathode of diode D2 is connected to the positive terminal of the CAN transceiver output, and the anode of diode D2 is connected to one end of transient suppression diode D3. The other end of transient suppression diode D3 is connected to the negative terminal of the CAN transceiver output.

4. The CAN redundancy and relay circuit based on domestically produced FPGA according to claim 1, characterized in that: An RC filter circuit is provided between the shielded twisted pair cable and the ground terminal of the CAN transceiver.

5. The CAN redundancy and relay circuit based on domestically produced FPGA according to claim 1, characterized in that: The FPGA's ground terminal is connected to the CAN transceiver's ground terminal and grounded at the same point. The FPGA's power supply terminal is connected to the CAN transceiver's power supply terminal and connected to power supply EP1. A filter capacitor is provided between the ground connection line and the power connection line.

6. A CAN redundancy and relay system based on a domestically produced FPGA, characterized in that: It includes a CAN bus, CAN nodes, CAN channels, and a data processing module. The CAN nodes are set on the CAN bus, and multiple CAN nodes are connected through the CAN channels. The CAN channels adopt the circuit described in any one of claims 1-5. The data processing module is connected to the CAN nodes and is used to selectively forward the data received by the CAN nodes. Each CAN node connects to two redundant CAN channels as input channels, and each CAN node connects to two redundant CAN channels as output channels; this system enables single-channel bidirectional or two-channel bidirectional data reception and forwarding.

7. The CAN redundancy and relay system based on domestically produced FPGA according to claim 6, characterized in that: The baud rate and data format of the CAN channel can be set via FPGA, and the baud rates of the CAN nodes at both ends of the CAN channel can be the same or different.

8. A communication method, characterized in that: This method is implemented based on the system described in claim 7 and includes the following steps: S01, the CAN node receives the data frame from the input channel and sends the data frame to the data processing module; S02. The data processing module parses the ID in the data frame. If the ID matches the local machine, the received data frame is a local data packet, which is then transmitted to the SOC of this node. If the ID does not match the local machine, then proceed to step S03. S03. Further parse the data frame to determine whether the data frame needs to be forwarded and the address of the target device for forwarding. If the data frame needs to be forwarded, proceed to step S04. If the data frame does not need to be forwarded, discard it or process it in this CAN node. S04. Perform electromagnetic interference removal and square wave shaping on the data frames that need to be forwarded to obtain reassembled data frames and send them back to the CAN bus.

9. The communication method according to claim 8, characterized in that: Step S03, the parsing of the data frame includes: Frame type extraction: The frame type is identified based on the frame header of the data frame. If it is a data frame, it is determined whether it needs to be forwarded. If it is a remote frame, the target device is matched according to the request data. If it is an error frame, it is discarded. If it is an overload frame, it is also discarded. Frame ID extraction: Extract the identifier ID of the data frame and determine the target device of the remote frame based on the ID; Error status determination is achieved by parsing the CRC checksum and ACK bit of the data frame to determine whether it is an error frame; Filtering and forwarding: In the CAN bus data link layer, an independent subnet is divided, key information of the CAN frame is parsed, and a decision is made on whether to forward the frame according to preset filtering rules.

10. The communication method according to claim 8, characterized in that: In step S04, electromagnetic interference mixed in during transmission is eliminated by using a low-pass filter and a differential signal comparator, and the attenuated distorted waveform is restored to a standard square wave conforming to the CAN specification. The rise / fall time of the standard square wave is ≤10% of the bit period.

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