CAN bus detection and analysis device

Abstract

The utility model provides a CAN (Controller Area Network) bus detection and analysis device, which comprises a CAN controller, a CAN transceiver and an interface protection circuit, the CAN controller receives detection data from a control unit and transmits the detection data to the CAN transceiver, the CAN transceiver is responsible for sending the data to a CAN bus or receiving the data from the CAN bus and transmitting the data to the CAN controller through the CAN bus interface protection circuit, and the CAN transceiver is responsible for receiving the data from the CAN bus and transmitting the data to the CAN controller. The transceiver receives the data and then transmits the data to the CAN controller, and the CAN controller sends the data to the self-control list; the protection circuit is divided into three stages, namely a first-stage macro-energy discharge circuit, a second-stage current limiting circuit and a third-stage voltage clamping circuit. According to the scheme, comprehensive protection and optimization measures are provided, so that the device can stably and reliably work in various complex environments, the safety and reliability of data communication are ensured, multi-stage protection measures are adopted in the interface protection circuit, effective protection is provided for differential mode and common mode interference, circuit damage or data loss is prevented, and the service life of the device is prolonged. And the service life of the device is prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of CAN bus detection, and particularly relates to a CAN bus detection and analysis device. Background Art

[0002] The CAN bus (Controller Area Network) is a serial communication network that effectively supports distributed control and real-time control, and has been widely used in the field of automatic control due to its high performance and high reliability. The detection and analysis of the CAN bus usually involve using a CAN bus analyzer or a CAN bus diagnostic tool. These tools can monitor, capture, and analyze the communication data on the CAN bus by connecting to the nodes on the CAN bus. Generally, the ESD and surge protection levels of common CAN transceiver chips are relatively low. For example, although the isolation withstand voltage of the SM1500 isolated CAN transceiver is 3500 VDC, in the case of bare machine monitoring, the CAN interface cannot meet the requirements of common surge tests. In the process of CAN bus detection and analysis, a supplementary protection circuit is also of great importance. The CAN bus analyzer or diagnostic tool itself is also an electronic device that needs to be protected from damage caused by reasons such as surge voltage, ESD, or EMI. The supplementary protection circuit can ensure that these devices are not affected by external interference during the test process and maintain their stability and reliability. In the process of CAN bus detection and analysis, accurate data acquisition is crucial. Any external interference or damage may cause data loss or distortion, thus affecting the accurate analysis of the system state. By using a supplementary protection circuit, these interferences can be minimized to ensure the accuracy of data acquisition. Therefore, in the process of CAN bus detection and analysis, it is necessary to add necessary protection circuits to meet the requirements. Using a supplementary protection circuit can ensure the safe and stable operation of the test equipment and the system under test, while improving the accuracy of data acquisition and the credibility of test results. Content of the Utility Model

[0003] Aiming at the defects and problems commonly existing in existing similar products, the utility model provides a CAN bus detection and analysis device.

[0004] The solution of the present utility model to solve its technical problems is as follows: A CAN bus detection and analysis device is adopted, which includes a CAN controller, a CAN transceiver, and also includes a CAN bus interface protection circuit. The CAN controller receives the detection data from the control unit and transmits it to the CAN transceiver. The CAN transceiver is responsible for sending the data to the CAN bus or receiving the data from the CAN bus and transmitting it to the CAN controller through the CAN bus interface protection circuit. After receiving the data, the transceiver transmits it to the CAN controller, and then the CAN controller sends it to the self-control unit. The protection circuit is divided into three levels: the first-level large-energy discharge circuit, the second-level current-limiting circuit, and the third-level voltage-clamping circuit. Among them, for the first-level large-energy discharge circuit: the A end and B end of the CAN bus detection terminal are connected in parallel with a gas discharge tube GDT. For the second-level current-limiting circuit: one end of resistor R1 and resistor R2 are respectively connected in series to the A end and B end of the CAN bus detection terminal. For the third-level voltage-clamping circuit: one end of the transient voltage suppression diode TVS1 is connected to the positive electrodes of diodes D1, D2, and D5 at the same time, and then the negative electrodes of diodes D1 and D2 are respectively connected to the other ends of resistor R1 and resistor R2, and the negative electrode of diode D5 is grounded. The other end of the transient voltage suppression diode TVS1 is connected to the negative electrodes of diodes D3, D2, and D6 at the same time, and then the positive electrodes of diodes D3 and D2 are respectively connected to the other ends of resistor R1 and resistor R2, and the positive electrode of diode D6 is grounded.

[0005] Further, the CANH terminal of the bus pin of the CAN transceiver is connected to the other end of resistor R1, the CANL terminal is connected to the other end of resistor R2, and VREF is grounded.

[0006] Further, after R3 is connected in series with VREF and then connected to the ground, and a capacitor C1 is connected in parallel at two points of resistor R3.

[0007] Further, between the CAN transceiver and the CAN bus protection circuit, there is also a CAN bus interface configuration circuit, which includes an opto-isolation circuit and a power isolation circuit.

[0008] Further, the opto-isolation circuit includes two opto-coupler chips 6N137. The TX0 port of the CAN controller is connected to the IN end of the first opto-coupler chip 6N137 through resistor one, the RX0 port of the CAN controller is connected to the OUT end of the second opto-coupler chip 6N137, and a resistor two is connected in series between the OUT end of the second opto-coupler chip 6N137 and the VCC end. The OUT port of the first opto-coupler chip 6N137 is connected to the TXD end of the CAN transceiver, the GNT end of the first opto-coupler chip 6N137 is connected to the GND end of the CAN transceiver, and a resistor three is connected in series between the OUT end of the first opto-coupler chip 6N137 and the VCC end. The IN port of the second opto-coupler chip 6N137 is connected to the RXD end of the CAN transceiver through resistor four.

[0009] Further, a capacitor C2 is connected in parallel between the GND terminal and the VCC terminal of the CAN transceiver; the RS terminal of the CAN transceiver is grounded after being connected in series with an adjustable resistor RL.

[0010] Further, the power isolation circuit is through a low-power DC / DC power isolation module.

[0011] Further, two 120Ω resistors must be connected to the end of the CAN bus.

[0012] The beneficial effects of the present utility model: The above solution provides comprehensive protection and optimization measures for the CAN bus detection and analysis device, enabling it to work stably and reliably in various complex environments, ensuring the security and reliability of data communication, and providing users with high-quality services and usage experiences.

[0013] 1. Improvement in anti-interference ability: Through the design of differential-mode and common-mode loops and the setting of the interface protection circuit, the anti-interference ability of the device is effectively improved. This enables the device to work stably in a complex electromagnetic environment and maintain good data transmission quality.

[0014] 2. Enhancement of protection function: Multiple protection measures are adopted in the interface protection circuit, including components such as transient suppression diodes and gas discharge tubes, providing effective protection against differential-mode and common-mode interference. This helps prevent circuit damage or data loss and extends the service life of the device.

[0015] 3. Improvement in circuit stability: By strictly controlling the equivalent capacitance of the protection circuit and selecting appropriate component parameters according to the design requirements, it is ensured that the device will not have an adverse impact on CAN bus communication during operation, improving the stability and reliability of the circuit.

[0016] 4. Strengthening of compatibility: Standard CAN controllers and transceivers are adopted to ensure the compatibility of the device with other CAN devices. At the same time, by setting up optoelectronic isolation circuits and power isolation circuits, the anti-interference ability of the device is enhanced, further improving its applicability in complex environments. The introduction of 120Ω resistors at the end ensures the matching of the bus impedance, avoiding reflection and signal distortion, and ensuring the reliability and stability of data communication. Description of the Drawings

[0017] Figure 1 is the CAN bus structure diagram;

[0018] Figure 2 is the protection circuit based on the CAN bus interface;

[0019] Figure 3 is the CAN bus interface configuration circuit diagram. Detailed Implementation Modes

[0020] The present utility model will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] Embodiment 1: A CAN bus detection and analysis device, as Figures 1 to 3 shown, includes a CAN controller (such as SJA1000), a CAN transceiver (such as 82C252 or SM1500), a CAN bus interface configuration circuit, and an interface protection circuit.

[0022] As Figure 1 shown, the CAN controller receives detection data from the control unit (microcontroller), processes it, and transmits it to the CAN transceiver. The CAN transceiver is responsible for sending data to the CAN bus or receiving data from the CAN bus and transmitting it to the CAN controller through the CAN bus interface configuration circuit and the interface protection circuit. The CAN data bus consists of two CAN-high and CAN-low data lines, transmitting differential signals. When a CAN bus node sends data, it broadcasts it in the form of a message to all nodes in the network. After receiving the data, the transceiver transmits it to the CAN controller, and the CAN controller then checks and determines whether it is the required data, and then sends it to the self-control unit (microcontroller).

[0023] As Figure 2 shown, the CAN bus interface protection circuit adds protection measures for the CAN bus, and reasonable protection can greatly improve the anti-interference ability of the interface. The protection circuit is divided into three levels. Label 1 is the first-level large-energy discharge circuit, label 2 is the second-level current-limiting circuit, and label 3 is the third-level voltage clamping. Each level of the circuit performs its own functions, and the combined action can achieve the best protection effect.

[0024] The first-level large-energy discharge circuit: The gas discharge tubes GDT are connected in parallel at the A and B ends of the CAN bus detection end; The second-level current-limiting circuit: One end of the resistors R1 and R2 are respectively connected in series at the A and B ends of the CAN bus detection end; The third-level voltage clamping: One end of the transient voltage suppression diode TVS1 is connected to the positive poles of the diodes D1, D2, and D5 at the same time, and then the negative poles of the diodes D1 and D2 are respectively connected to the other ends of the resistors R1 and R2, and the negative pole of the diode D5 is grounded; The other end of the transient voltage suppression diode TVS1 is connected to the negative poles of the diodes D3, D2, and D6 at the same time, and then the positive poles of the diodes D3 and D2 are respectively connected to the other ends of the resistors R1 and R2, and the positive pole of the diode D6 is grounded. The CANH end of the bus pin of the CAN transceiver (82C252) is connected to the other end of the resistor R1, the CANL end is connected to the other end of the resistor R2, and VREF is grounded. At the same time, after R3 is connected in series with VREF and then connected to the ground, and a capacitor C1 is connected in parallel at two points of the resistor R3.

[0025] The above interface protection circuit implements a differential-mode loop and a common-mode loop. When a differential-mode interference voltage is applied to terminals A and B of the interface, transient voltage suppression diode TVS1 responds and conducts first, clamping the voltage between the CANH and CANL bus pins of chip PCA 82C252. Resistors R1 and R2 limit the current flowing through TVS1 to prevent it from being damaged due to over-power. Gas discharge tube GDT responds the slowest and conducts last, discharging most of the energy and limiting the residual voltage to a lower level.

[0026] In the common-mode loop, to ensure good protection effect, the communication reference ground VREF should be grounded at a single point after networking. When a common-mode interference voltage is applied to terminals A and B of the interface, TVS1 responds and conducts first, clamping the voltage between the chip bus pin and VREF. Resistors R1 and R2 limit the current flowing through TVS1 to prevent it from being damaged due to over-power. Gas discharge tube GDT responds the slowest and conducts last, discharging most of the energy and limiting the residual voltage to a lower level.

[0027] For common-mode interference, VREF needs to use the ground (or protective ground) as the discharge loop. The interface protection circuit must be reliably grounded, otherwise the common-mode protection part will fail, which may cause damage to the previous-stage chip or circuit.

[0028] Since the CAN bus has extremely high requirements for bus capacitance, the equivalent capacitance of the protection circuit itself should be reduced as much as possible. Designed according to the Figure 2 circuit structure shown, the total differential capacitance C1 of the interface protection circuit can be controlled at about 10 pF, basically avoiding the impact on CAN bus communication while providing sufficient protection.

[0029] Based on the above protection circuit, the breakdown current of gas discharge tube GDT can be selected as 500 A, the breakdown voltage is 90 V, and the package is 1206. If there is enough space, a device with a larger breakdown current can be selected to obtain a better protection effect. The breakdown voltage of transient voltage suppression diode TVS should be higher than the signal amplitude and lower than the maximum DC withstand voltage of 12 V of the pin.

[0030] As Figure 3As shown, in practical applications, the CAN bus interface configuration circuit uses the 82C250 from Philips as the interface between the CAN controller and the physical bus, that is, the CAN transceiver, to enhance the differential transmission ability of the bus and the differential reception ability of the CAN controller (when using the SM1500, VREF becomes CANG). To further enhance the anti-interference ability, an optoelectronic isolation circuit 4 is set between the CAN controller and the transceiver. The optoelectronic isolation circuit 4 includes two optocoupler chips 6N137. The TX0 port of the CAN controller (SJA1000) is connected to the IN end of the first optocoupler chip 6N137 through the resistor R11, the RX0 port of the CAN controller (SJA1000) is connected to the OUT end of the second optocoupler chip 6N137, and a resistor R12 is connected in series between the OUT end of the second optocoupler chip 6N137 and the VCC end; the OUT port of the first optocoupler chip 6N137 is connected to the TXD end of the CAN transceiver (82C252), the GNT end of the first optocoupler chip 6N137 is connected to the GND end of the CAN transceiver (82C252), and a resistor R13 is connected in series between the OUT end of the first optocoupler chip 6N137 and the VCC end; the IN port of the second optocoupler chip 6N137 is connected to the RXD end of the CAN transceiver (82C252) through the resistor R14. A capacitor C2 is connected in parallel between the GND end and the VCC end of the CAN transceiver (82C252). The RS end of the CAN transceiver (82C252) is grounded after being connected in series with the adjustable resistor RL.

[0031] Figure 3 In it, the power isolation circuit (labeled 5) is used to ensure that the power supplies Vdd and Vcc used on both sides of the optoelectronic isolation device are completely isolated, otherwise the optoelectronic isolation will lose its due function. The isolation of the power supply can be achieved through a low-power DC / DC power isolation module. The optoelectronic isolation circuit can be selected according to the different on-site transmission distances and electromagnetic interference situations. If the distance is short and the electromagnetic interference is small, optoelectronic isolation can be not adopted to achieve the maximum communication rate or distance, and the interface circuit can be simplified. If optoelectronic isolation is required, high-speed optoelectronic isolation devices such as the high-speed optocoupler 6N137 should be selected, whose transmission delay time is short, and the typical value is only 48 ns, which is already close to the level of the transmission delay time of the TTL circuit.

[0032] Figure 3The transmission data input terminal TXD of the CAN transceiver 82C250 is connected to the output terminal OUT of the first optocoupler 6N137. Among them, the TXD must be connected to the pull-up resistor R13 at the same time. The function of R13 is to ensure that a low level is output when the photosensitive triode is conducting and a high level is output when it is cut off, which also meets the requirements of the CAN bus. According to the regulations of the CAN bus, the bus should be recessive during the idle period, that is, the default state of the nodes in the CAN network is recessive. Therefore, the default state of the TXD terminal of the 82C250 should be logic 1 (high level). Therefore, through R13, it can be ensured that the state of the TXD terminal is logic 1 (high level) when no data is sent or abnormal conditions occur.

[0033] During the detection process, two 120Ω resistors must be connected to the end of the CAN bus. They are crucial for the impedance matching of the bus and cannot be omitted. Otherwise, the reliability and anti-interference ability of the bus data communication will be severely reduced, and even communication failure may occur.

[0034] Through these designs, the reliability and stability of the CAN bus detection and analysis device are ensured, enabling it to work effectively in a complex environment, protecting the bus from external interference, and ensuring the reliable transmission of data and the smooth progress of communication.

[0035] When the above solution is implemented, first, the user installs the CAN bus detection and analysis device in the CAN bus system to be monitored. Ensure that the device is correctly connected to the CAN bus node and connect the 120Ω resistor at the end according to the design requirements. Start the CAN bus detection and analysis device and turn on the power supply. The device performs self-check and configures the interface protection circuit and other functional modules according to the preset parameters. The device starts to monitor the data transmission activities on the CAN bus. Through the CAN controller and transceiver, the device receives and analyzes the data packets on the CAN bus in real time and performs corresponding analysis and processing. During the data acquisition process, the device continuously monitors the interference situation on the CAN bus. The differential-mode and common-mode interferences are detected and suppressed through the interface protection circuit to protect the CAN bus from external interference. When the device detects an abnormal situation or an event that requires the user's attention, it will prompt the user through methods such as interface display or alarm signals. The user can perform further analysis and processing based on the data and information provided by the device. If necessary, the user can adjust the parameters of the device according to the actual situation, such as adjusting the sensitivity or parameters of the protection circuit, to optimize the performance of the device and adapt to different working environments. After completing the data acquisition and analysis tasks, the user can choose to turn off the CAN bus detection and analysis device to end the monitoring process. At the same time, necessary maintenance and inspections can be carried out on the device to ensure its long-term stable and reliable operation.

[0036] The above specific embodiments of the present utility model are only used for exemplary illustration or explanation of the principle of the present utility model, and do not constitute a limitation on the present utility model. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A CAN bus detection and analysis device, comprising a CAN controller and a CAN transceiver, characterized in that: It also includes a CAN bus interface protection circuit. The CAN controller receives detection data from the control unit and transmits it to the CAN transceiver. The CAN transceiver is responsible for sending data to the CAN bus or receiving data from the CAN bus and transmitting it to the CAN controller through the CAN bus interface protection circuit. After receiving the data, the transceiver transmits it to the CAN controller, and the CAN controller sends it to the self-control unit; the protection circuit is divided into three levels: the first level large energy discharge circuit, the second level current limiting circuit, and the third level voltage clamping circuit; among them, the first level large energy discharge circuit: the gas from the CAN bus detection end A and the B end in parallel GDT; the second-stage current limiting circuit: the detection terminals A and B of the CAN bus are connected in series with one end of the resistor R1 and one end of the resistor R2 respectively; the third-stage voltage clamping circuit: after one end of the transient suppression diode TVS1 is simultaneously connected to the positive electrodes of the diodes D1, D2 and D5, the negative electrodes of the diodes D1 and D2 are respectively connected to the other ends of the resistors R1 and R2, and the negative electrode of the diode D5 is grounded; after the other end of the transient suppression diode TVS1 is simultaneously connected to the negative electrodes of the diodes D3, D2 and D6, the positive electrodes of the diodes D3 and D2 are respectively connected to the other ends of the resistors R1 and R2, and the positive electrode of the diode D6 is grounded.

2. The CAN bus detection and analysis device according to claim 1, characterized in that: The bus pin CANH end of the CAN transceiver is connected to the other end of the resistor R1, the CANL end is connected to the other end of the resistor R2, and VREF is grounded.

3. The CAN bus detection and analysis device according to claim 1, characterized in that: VREF is connected in series with R3 and then to the ground, and capacitor C1 is connected in parallel between the two points of resistor R3.

4. The CAN bus detection and analysis device according to claim 1, characterized in that: A CAN bus interface configuration circuit is also connected between the CAN transceiver and the CAN bus protection circuit, including a photoelectric isolation circuit and a power isolation circuit.

5. The CAN bus detection and analysis device according to claim 4, characterized in that: The photoelectric isolation circuit includes two optical coupling chips 6N137, the TX0 port of the CAN controller is connected to the IN terminal of the first optical coupling chip 6N137 through a resistor 1, the RX0 port of the CAN controller is connected to the OUT terminal of the second optical coupling chip 6N137, and a resistor 2 is connected in series between the OUT terminal and the VCC terminal of the second optical coupling chip 6N137; the OUT port of the first optical coupling chip 6N137 is connected to the TXD terminal of the CAN transceiver, the GNT terminal of the first optical coupling chip 6N137 is connected to the GND terminal of the CAN transceiver, and a resistor 3 is connected in series between the OUT terminal and the VCC terminal of the first optical coupling chip 6N137; the IN port of the second optical coupling chip 6N137 is connected to the RXD terminal of the CAN transceiver through a resistor 4.

6. The CAN bus detection and analysis device according to claim 4, characterized in that: A capacitor C2 is connected in parallel between the GND terminal and the VCC terminal of the CAN transceiver; an adjustable resistor RL is connected in series to the RS terminal of the CAN transceiver and then grounded.

7. The CAN bus detection and analysis device according to claim 4, characterized in that: The power isolation circuit uses a low-power DC / DC power isolation module.

8. The CAN bus detection and analysis device according to claim 1, characterized in that: Two 120Ω resistors must be connected to the ends of the CAN bus.

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