Lossless wire-breaking-free automobile CAN bus testing device

Abstract

The utility model discloses a lossless wire-breaking-free automobile CAN bus testing device, and the device is characterized in that an induction signal interface is connected with a conductive clamp, and is used for obtaining a surface induction signal of a CAN signal wire; the CAN signal extraction module is connected with the induction signal interface and is used for converting a surface induction signal of a CAN signal line into a logic signal; the CAN signal conversion module is connected with the CAN signal extraction module, the main control module and the CAN signal interface and used for converting logic signals from the CAN signal extraction module or the main control module into CAN signals and sending the CAN signals to the CAN signal interface and converting the CAN signals received from the CAN signal interface into logic signals and sending the logic signals to the main control module, and the display module is connected with the main control module. And the display module is used for displaying CAN signal identification data information. By using the CAN bus signal acquisition device, a user can conveniently acquire a CAN bus signal without damaging a CAN communication line or additionally arranging a terminal during automobile maintenance, so that the maintenance efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of automobile equipment detection, concretely relates to a nondestructive free broken line automobile CAN bus testing arrangement. BACKGROUND

[0002] In the process of repairing the automobile electrical module, the communication line voltage is often normal but cannot communicate. The traditional solution needs to use the CAN analyzer connected to the computer software to check the communication data, which has a higher requirement for the professional ability level of the user, and the number of detection and repair equipment is large, the site space is large, the connection arrangement operation is complicated, and the carrying is not convenient.

[0003] Chinese patent CN202322788969.7 proposes a testing device for detecting vehicle CAN serial port and LIN serial port performance, which can be connected to the communication interface through the probe, and the data communication condition of CAN signal or LIN signal can be observed through the display window of the device. When the device is used to collect CAN signal, it needs to be directly connected to the communication medium of CAN signal through the probe, that is, CAN signal can only be collected by directly connecting CAN signal socket or cutting open CAN signal line, which will bring inconvenience to repair and even cause equipment damage.

[0004] Therefore, a new device needs to be proposed to solve the above problems. UTILITY MODEL CONTENT

[0005] To solve the problems existing in the prior art, the utility model provides a kind of automobile communication bus testing device with wireless signal display embodiment, when detecting automobile CAN bus communication signal, the damage to CAN communication line can be avoided, CAN bus communication signal is obtained from the surface of CAN signal line by conducting clamp, and the use of user is facilitated.

[0006] The technical scheme adopted by the utility model is as follows:

[0007] The application discloses a nondestructive and wire-breaking-free automobile CAN bus testing device, which comprises an induction signal interface, a CAN signal interface, a CAN signal extraction module, a CAN signal conversion module, a main control module, a display module and a power module; the induction signal interface is connected with a conductive clamp and used for acquiring a surface induction signal of a CAN signal line; the CAN signal extraction module is connected with the induction signal interface and used for converting the surface induction signal of the CAN signal line into a logic signal; the CAN signal conversion module is connected with the CAN signal extraction module, the main control module and the CAN signal interface, used for converting the logic signal from the CAN signal extraction module or the main control module into a CAN signal and sending the CAN signal to the CAN signal interface, and converting a CAN signal received from the CAN signal interface into a logic signal and sending the logic signal to the main control module; the display module is connected with the main control module and used for displaying CAN signal identification data information; and the power module is used for providing an adaptive power supply for the device.

[0008] Further, the conductive clamp comprises a conductive contact arranged at a clamping portion of the conductive clamp, and the conductive contact is connected with the induction signal interface through a wire.

[0009] Further, the device further comprises a polarity switching module connected between the induction signal interface and the CAN signal extraction module, which is used for switching the polarity of the connection between the induction signal interface and the CAN signal extraction module according to the control of the main control module.

[0010] Further, the polarity switching module comprises a relay K1 and a switch tube Q5, a first normally open end and a second normally closed end of the relay K1 are connected with a positive end of the induction signal interface, a second normally open end and a first normally closed end of the relay K1 are connected with a negative end of the induction signal interface, a first common end of the relay K1 is connected with a low CAN induction signal end, a second common end of the relay K1 is connected with a high CAN induction signal end, and a signal polarity control end of the main control module controls the power supply or power loss of a coil of the relay K1 through the switch tube Q5.

[0011] Further, the CAN signal extraction module comprises a first comparator, a second comparator, an AND logic operation unit, and a NOR logic operation unit; the positive input end of the first comparator is connected to the CAN sensing high signal end, and the negative input end is connected to the CAN sensing low signal end; the CAN sensing high signal end is connected to the negative input end of the second comparator after being divided by the resistor R12 and the resistor R17; the CAN sensing low signal end is connected to the power supply of the CAN signal extraction module via the resistor R13 and the resistor R21; the connection point of the resistor R13 and the resistor R21 is also connected to the positive input end of the second comparator; the output end of the second comparator is connected to one input end of the NOR logic operation unit; the other input end of the NOR logic operation unit is grounded; the output end of the NOR logic operation unit is connected to one input end of the AND logic operation unit; the other input end of the AND logic operation unit is connected to the output end of the first comparator; and the output end of the AND logic operation unit is connected to the output end of the NOR logic operation unit and serves as the output end of the CAN signal extraction module.

[0012] Further, the CAN signal conversion module comprises a CAN signal conversion chip U2 and a CAN signal conversion chip U4; the CANH and CANL pins of the CAN signal conversion chip U2 and the CAN signal conversion chip U4 are both connected to the CAN signal interface; the TXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal sending end of the master control module; the RXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal receiving end of the master control module; and the TXD pin of the CAN signal conversion chip U2 is connected to the output end of the CAN signal extraction module.

[0013] Further, the power module comprises a battery, a switch tube Q1, a switch tube Q2, a double-end diode D4, a power switch, a resistor R9, a resistor R16, a capacitor C9, a first voltage conversion unit and a second voltage conversion unit; a positive pole of the battery is connected with a source pole of the switch tube Q1, a gate pole of the switch tube Q1 is connected with a drain pole of the switch tube Q2, a source pole of the switch tube Q2 is grounded, a gate pole of the switch tube Q2 is connected with a power control end of the main control module, the resistor R16 is connected in parallel between the gate pole and the source pole of the switch tube Q2; the resistor R9 is connected in parallel between the gate pole and the source pole of the switch tube Q1, the gate pole of the switch tube Q1 is also connected with one anode of the double-end diode D4, a cathode of the diode D4 is grounded through the power switch, the other anode of the double-end diode D4 is connected with a switch detection end of the main control module and one end of the capacitor C9, the other end of the capacitor C9 is grounded; a drain pole of the switch tube Q1 is connected with an input end of the first voltage conversion unit, an output end of the first voltage conversion unit is connected with an input end of the second voltage conversion unit; the first voltage conversion unit is used for converting the battery output voltage into 5V voltage, and the second voltage conversion unit is used for converting the 5V voltage into 3.3V voltage.

[0014] Further, the display module comprises an OLED display screen.

[0015] Further, the shell is further provided with a CAN signal extraction module, a CAN signal conversion module, a main control module and a power module.

[0016] The utility model discloses beneficial effects are:

[0017] The utility model provides a kind of nondestructive free broken line automobile CAN bus testing device, user will electrically conductive clamp be clamped in the surface of automobile CAN signal line, when CAN signal line has communication signal, inductive signal is generated in the electrically conductive clamp of CAN signal line surface, and it is accessed into device by inductive signal interface.CAN signal extraction module converts CAN signal line surface inductive signal into logic signal, and logic signal is output to main control module on one hand, and it is shown by display module;Logic signal is output to CAN signal conversion module on the other hand, and it is converted into the CAN signal of the differential signal form that CAN bus can be transmitted, and then it is output by CAN signal interface.In some applications, CAN signal analysis equipment can be connected to CAN signal interface to analyze nondestructively obtained CAN signal.In some applications, user can also directly obtain differential form CAN signal from CAN signal interface, and it is output to main control module after being converted into logic signal by CAN signal conversion module, and it is shown by display module.By using the utility model embodiment, user can conveniently obtain CAN bus signal in automobile maintenance, without damaging CAN communication line or setting terminal, and maintenance efficiency can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is the electrical principle block diagram of the utility model a kind of nondestructive free broken line automobile CAN bus testing device embodiment;

[0019] Figure 2 It is the structural schematic diagram of the utility model a kind of nondestructive free broken line automobile CAN bus testing device embodiment;

[0020] Figure 3 It is the electrical principle block diagram of another utility model a kind of nondestructive free broken line automobile CAN bus testing device embodiment;

[0021] Figure 4 It is the circuit principle diagram of polarity switching module;

[0022] Figure 5 It is the circuit principle diagram of CAN signal extraction module;

[0023] Figure 6 It is the electrical principle block diagram of CAN signal conversion module;

[0024] Figure 7 It is the electrical principle block diagram of power module.

[0025] In the figure:

[0026] 100 - shell, 200 - inductive signal interface, 210 - conductive clamp, 220 - wire, 300 - CAN signal interface, 400 - CAN signal extraction module, 500 - CAN signal conversion module, 600 - main control module, 700 - display module, 800 - power module, 810 - button, 900 - polarity switching module. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0028] The terms "first", "second", "third" in the present application are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number or order of the indicated technical features. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship or movement condition between components in a certain posture (as shown in the drawings); it should be noted that when a component is referred to as "fixed to", "provided on", "connected to" another component, it can be directly on another component or there can be a middle component. When a component is considered as "connected" to another component, it can be directly connected to another component, or there can be one or more middle components. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for illustrative purposes, and are not the only embodiment.

[0029] As Figures 1-7 shown, to solve the problems existing in the prior art, the utility model provides a kind of loss-free exempt from breaking line automobile CAN bus testing device embodiment, when detecting automobile CAN bus communication signal, the damage to CAN communication line can be avoided, CAN bus communication signal is obtained from the surface of CAN signal line by conductive clamp, and it is convenient for user's use.

[0030] Specifically, referring to Figure 1 and Figure 2The utility model discloses a kind of non-destructive free-wire automobile CAN bus testing device, comprising: inductive signal interface 200, CAN signal interface 300, CAN signal extraction module 400, CAN signal conversion module 500, main control module 600, display module 700 and power module 800;Inductive signal interface 200 connects conducting clamp 210, for obtaining CAN signal line surface inductive signal;CAN signal extraction module 400 connects inductive signal interface 200, for converting CAN signal line surface inductive signal into logic signal;CAN signal conversion module 500 connects CAN signal extraction module 400, main control module 600 and CAN signal interface 300, for converting the logic signal from CAN signal extraction module 400 or main control module 600 into CAN signal and sending to CAN signal interface 300, and converting the CAN signal received from CAN signal interface 300 into logic signal and sending to main control module 600, display module 700 connects main control module 600, for displaying CAN signal identification data information;Power module 800 is used to provide adaptive power supply for device.

[0031] The working principle of the embodiment of the utility model is:

[0032] User clamps conducting clamp 210 on the surface of CAN signal line of automobile, when there is communication signal in CAN signal line, inductive signal is generated on conducting clamp 210 on the surface of CAN signal line, and is accessed to the device through inductive signal interface 200.CAN signal extraction module 400 converts CAN signal line surface inductive signal into logic signal, and the logic signal is output to main control module on one side, and is displayed by display module 700;The logic signal is output to CAN signal conversion module 500 on the other side, and is converted into CAN signal in the form of differential signal that can be transmitted on CAN bus, and then is output through CAN signal interface 300.In some applications, other CAN signal analysis equipment can be connected to CAN signal interface 300 to analyze the non-destructive CAN signal obtained.In some applications, user can also directly obtain differential form CAN signal from CAN signal interface 300, and output to main control module after conversion into logic signal by CAN signal conversion module 500, and display by display module 700.

[0033] By using the embodiment of the utility model, user can conveniently obtain CAN bus signal in automobile maintenance, without damaging CAN communication line or setting another terminal, and maintenance efficiency can be improved.

[0034] It should be noted that, in specific implementation, main control module 600 can be microprocessor, for example, model is APM32F072.

[0035] In some embodiments, the conductive clamp 210 comprises a conductive contact provided on the clamping portion of the conductive clamp, which is connected to the induction signal interface 200 through the wire 220. In use, when the conductive clamp 210 is clamped on the surface of the CAN signal line, the conductive contact is in contact with the surface of the CAN signal line, and when there is a communication signal in the CAN signal line, an induction signal is generated on the conductive contact of the conductive clamp 210, which is transmitted to the induction signal interface 200 through the wire 220.

[0036] In some embodiments, referring to Figure 3 The non-destructive and non-breaking line automobile CAN bus testing device further comprises a polarity switching module 900 connected between the induction signal interface 200 and the CAN signal extraction module 400, which is used to switch the polarity of the connection between the induction signal interface 200 and the CAN signal extraction module 400 according to the control of the main control module 600. In use, the user does not need to deliberately adjust the polarity of the connection of the conductive clamp 210 to the CAN signal line to obtain the CAN signal.

[0037] In some embodiments, referring to Figure 4 The polarity switching module 900 comprises a relay K1, a diode D8, a switch tube Q5 and a resistor R14. The first normally open end NO1 and the second normally closed end NC2 of the relay K1 are connected to the positive end P+ of the induction signal interface, the second normally open end NO2 and the first normally closed end NC1 of the relay K1 are connected to the negative end P- of the induction signal interface, the first common end COM1 of the relay K1 is connected to the CAN induction low signal end CANL, the second common end COM2 of the relay K1 is connected to the CAN induction high signal end CANH, and the signal polarity control end CANHL of the main control module controls the energization or de-energization of the coil of the relay K1 through the switch tube Q5.

[0038] In a specific implementation, the switch tube Q5 is an NMOS tube, the gate of the switch tube Q5 is connected to the signal polarity control end CANHL of the main control module 600, the source of the switch tube Q5 is grounded, the resistor R14 is connected between the gate and the source, the coil of the relay K1 is connected between the drain of the switch tube Q5 and the 5V power supply VCC-5V, the cathode of the diode D8 is connected to the 5V power supply VCC-5V, and the anode is connected to the drain of the switch tube Q5.

[0039] The main control module 600 switches the polarity of the connection between the sensing signal interface 200 and the CAN signal extraction module 400 by controlling the level of the signal polarity control end CANHL. When the signal polarity control end CANHL is at a high level, the coil of the relay K1 is powered, the first common end COM1 is connected to the first normally open end NO1, and the second common end COM2 is connected to the second normally open end NO2. At this time, the positive end P+ of the sensing signal interface 400 is connected to the CAN sensing low signal end CANL, and the negative end P- of the sensing signal interface 400 is connected to the CAN sensing high signal end CANH. When the signal polarity control end CANHL is at a low level, the coil of the relay K1 is de-energized, the first common end COM1 is connected to the first normally closed end NC1, and the second common end COM2 is connected to the second normally closed end NC2. At this time, the positive end P+ of the sensing signal interface 400 is connected to the CAN sensing high signal end CANH, and the negative end P- of the sensing signal interface 400 is connected to the CAN sensing low signal end CANL. After the device is powered on, the relay K1 is continuously switched by the signal polarity control end CANHL until the main control module 600 receives the CAN signal. Subsequently, the state of the relay K1 is fixed and no longer switched.

[0040] In some embodiments, referring to Figure 5 , the CAN signal extraction module 400 includes a first comparator U6A, a second comparator U6B, an AND logic operation unit U9, an OR NOT logic operation unit U10, a resistor R12, a resistor R17, a resistor R13, and a resistor R21. The positive input end of the first comparator U6A is connected to the CAN sensing high signal end CANH, and the negative input end is connected to the CAN sensing low signal end CANL. The CAN sensing high signal end CANH is connected to the negative input end of the second comparator U6B after being divided by the resistor R12 and the resistor R17. The CAN sensing low signal end CANL is connected to the CAN signal extraction module power supply VCC-5VA through the resistor R13 and the resistor R21. The connection point of the resistor R13 and the resistor R21 is also connected to the positive input end of the second comparator U6B. The output end of the second comparator U6B is connected to one input end of the OR NOT logic operation unit U10. The other input end of the OR NOT logic operation unit U10 is grounded. The output end of the OR NOT logic operation unit U10 is connected to one input end of the AND logic operation unit U9. The other input end of the AND logic operation unit U9 is connected to the output end of the first comparator U6A. The output end of the AND logic operation unit U9 is connected to the output end of the OR NOT logic operation unit U10 and serves as the output end TC of the CAN signal extraction module.

[0041] In specific implementations, the transmission standard of the CAN bus is divided into high-speed and low-speed fault tolerance, and the data state includes explicit state and implicit state. According to the voltage of the CAN bus signal high end and the signal high end in different states, the output end TC of the CAN signal extraction module 400 outputs a high-level or low-level logic signal.

[0042] For example, when the transmission standard of the CAN bus is high speed and the data state is dominant, the signal high end voltage is about 3.5V and the signal low end voltage is about 1.5V; when the transmission standard of the CAN bus is low speed fault tolerance and the data state is dominant, the signal high end voltage is about 4V and the signal low end voltage is about 1V; in these two cases, the setting of the multiple resistance values in the CAN signal extraction module can make the positive input end level of the second comparator U6B lower than the negative input end level, the second comparator U6B outputs a low level, or the non-logic operation unit U10 outputs a high level, so that the output end TC of the CAN signal extraction module outputs a high level. When the transmission standard of the CAN bus is high speed and the data state is recessive, the signal high end voltage and the signal low end voltage are both close to 2.5V; when the transmission standard of the CAN bus is low speed fault tolerance and the data state is recessive, the signal high end voltage is about 1.75V and the signal low end voltage is about 3.25V; in these two cases, the setting of the multiple resistance values in the aforementioned CAN signal extraction module can also make the positive input end level of the second comparator U6B higher than the negative input end level, the second comparator U6B outputs a high level, or the non-logic operation unit U10 outputs a low level, so that the output end TC of the CAN signal extraction module 400 outputs a low level. Other resistance and capacitor devices play a role in signal conditioning and filtering, which will not be described here.

[0043] In some embodiments, referring to Figure 6 The CAN signal conversion module 500 includes the CAN signal conversion chip U2 and the CAN signal conversion chip U4, the CANH and CANL pins of the CAN signal conversion chip U2 and the CAN signal conversion chip U4 are connected to the CAN signal interface, the TXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal sending end CAN_TXD of the master control module, the RXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal receiving end CAN_RXD of the master control module, and the TXD pin of the CAN signal conversion chip U2 is connected to the output end TC of the CAN signal extraction module 400.

[0044] In specific implementation, the logic signal obtained by the CAN signal extraction module 400 is converted into a differential form of CAN signal by the CAN signal conversion chip U4. The logic signal sent by the master control module 600 is converted into a differential form of CAN signal by the CAN signal conversion chip U2 and sent to the CAN signal interface 300. The differential form of CAN signal received by the CAN signal interface 300 is converted into a logic signal by the signal conversion chip U2 and sent to the master control module 600.

[0045] In some embodiments, referring to Figure 7The power module 800 comprises a battery, a switch tube Q1, a switch tube Q2, a double-end diode D4, a power switch KEY1, a resistor R9, a resistor R16, a capacitor C9, a first voltage conversion unit and a second voltage conversion unit; a positive pole of the battery is connected to a source pole of the switch tube Q1, a gate pole of the switch tube Q1 is connected to a drain pole of the switch tube Q2, a source pole of the switch tube Q2 is grounded, a gate pole of the switch tube Q2 is connected to a power control end POW_EN of the master control module, the resistor R16 is connected in parallel between the gate pole and the source pole of the switch tube Q2; the resistor R9 is connected in parallel between the gate pole and the source pole of the switch tube Q1, the gate pole of the switch tube Q1 is further connected to one anode of the double-end diode D4, a cathode of the diode D4 is grounded through the power switch KEY1, the other anode of the double-end diode D4 is connected to a switch detection end SW of the master control module and one end of the capacitor C9, the other end of the capacitor C9 is grounded; the drain pole of the switch tube Q1 is connected to an input end of the first voltage conversion unit, an output end of the first voltage conversion unit is connected to an input end of the second voltage conversion unit; the first voltage conversion unit is used for converting the battery output voltage into a 5V voltage, and the second voltage conversion unit is used for converting the 5V voltage into a 3.3V voltage. The switch tube Q1 is a PMOS tube, and the switch tube Q2 is an NMOS tube.

[0046] In a specific implementation, the power switch KEY1 is turned on through the button 810, when the user long-presses the button 810, the power switch KEY1 is turned on, the source pole of the switch tube Q1 is grounded through the double-end diode D4 and the power switch KEY1, the switch tube Q1 is saturated and turned on, the battery supplies power to the device through the fuse F1, thereafter, the switch tube Q2 is saturated and turned on through the power control end POW_EN of the master control module 600 being high level, thereby keeping the switch tube Q1 in the turned-on state. When the user long-presses the button 810 again, the power switch KEY1 is turned on, the switch detection end SW of the master control module 600 is set to low level, thereafter, the switch tube Q2 is turned off through the power control end POW_EN of the device master control module 600 being low level, and the switch tube Q1 is turned off after the user releases the button 810, thereby achieving power-off shutdown.

[0047] In some embodiments, referring to Figure 2 The display module 700 comprises an OLED display screen 710.

[0048] In some embodiments, referring to Figure 2 The shell 100, the inductive signal interface 200, the CAN signal interface 300, the OLED display screen 710 and the button 810 are arranged on the surface of the shell 100, and parts of the CAN signal extraction module 400, the CAN signal conversion module 500, the master control module 600 and the power module 800 are arranged on the circuit board embedded in the shell 100.

[0049] The utility model is not limited to the above optional implementation, and anyone can draw other various forms of products under the enlightenment of the utility model, but no matter any change in shape or structure, any technical scheme falling into the scope defined by the utility model claims falls within the protection scope of the utility model.

Claims

1. A non-destructive, wire-free, automotive CAN bus testing device, characterized in that, The device comprises an induction signal interface, a CAN signal interface, a CAN signal extraction module, a CAN signal conversion module, a main control module, a display module and a power module; the induction signal interface is connected with a conductive clamp for obtaining a surface induction signal of a CAN signal line; the CAN signal extraction module is connected with the induction signal interface for converting the surface induction signal of the CAN signal line into a logic signal; the CAN signal conversion module is connected with the CAN signal extraction module, the main control module and the CAN signal interface for converting the logic signal from the CAN signal extraction module or the main control module into a CAN signal and sending the CAN signal to the CAN signal interface, and converting a CAN signal received from the CAN signal interface into a logic signal and sending the logic signal to the main control module; the display module is connected with the main control module for displaying CAN signal identification data information; and the power module is used for providing an adaptive power supply for the device. The conductive clamp comprises a conductive contact arranged at a clamping portion of the conductive clamp, and the conductive contact is connected with the induction signal interface through a wire.

2. The nondestructive and nonbreaking-wire automobile CAN bus testing device according to claim 1, wherein, The device further comprises a polarity switching module connected between the induction signal interface and the CAN signal extraction module for switching a polarity of the induction signal interface connected with the CAN signal extraction module according to a control of the main control module.

3. The nondestructive and nonbreaking-wire automobile CAN bus testing device according to claim 1, wherein, The polarity switching module comprises a relay K1 and a switch tube Q5, a first normally open end and a second normally closed end of the relay K1 are connected with a positive terminal of the induction signal interface, a second normally open end and a first normally closed end of the relay K1 are connected with a negative terminal of the induction signal interface, a first common terminal of the relay K1 is connected with a CAN induction low signal terminal, a second common terminal of the relay K1 is connected with a CAN induction high signal terminal, and a signal polarity control terminal of the main control module controls the relay K1 to be powered or unpowered through the switch tube Q5.

4. The nondestructive, break-free automotive CAN bus testing device of claim 3, wherein, The CAN signal extraction module comprises a first comparator, a second comparator, an AND logic operation unit and a NOR logic operation unit; a positive input terminal of the first comparator is connected with the CAN induction high signal terminal, a negative input terminal of the first comparator is connected with the CAN induction low signal terminal, the CAN induction high signal terminal is connected with a negative input terminal of the second comparator through voltage division of resistors R12 and R17, the CAN induction low signal terminal is connected with a power supply of the CAN signal extraction module through resistors R13 and R21, and a connection point of the resistors R13 and R21 is also connected with a positive input terminal of the second comparator; an output terminal of the second comparator is connected with an input terminal of the NOR logic operation unit, another input terminal of the NOR logic operation unit is grounded, an output terminal of the NOR logic operation unit is connected with an input terminal of the AND logic operation unit, another input terminal of the AND logic operation unit is connected with an output terminal of the first comparator, and an output terminal of the AND logic operation unit is connected with an output terminal of the NOR logic operation unit and serves as an output terminal of the CAN signal extraction module.

5. The nondestructive, break-free automotive CAN bus testing device of claim 1, wherein, ​ 6. The nondestructive, break-free automotive CAN bus testing device of claim 5, wherein, The CAN signal conversion module comprises CAN signal conversion chip U2 and CAN signal conversion chip U4, the CANH and CANL pins of the CAN signal conversion chip U2 and the CAN signal conversion chip U4 are connected to the CAN signal interface, the TXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal sending end of the master control module, the RXD pin of the CAN signal conversion chip U2 is connected to the CAN logic signal receiving end of the master control module, and the TXD pin of the CAN signal conversion chip U2 is connected to the output end of the CAN signal extraction module.

7. The nondestructive, break-free automotive CAN bus testing device of claim 1, wherein, The power module comprises a battery, a switch tube Q1, a switch tube Q2, a double-end diode D4, a power switch, a resistor R9, a resistor R16, a capacitor C9, a first voltage conversion unit and a second voltage conversion unit; the positive pole of the battery is connected to the source electrode of the switch tube Q1, the gate electrode of the switch tube Q1 is connected to the drain electrode of the switch tube Q2, the source electrode of the switch tube Q2 is grounded, the gate electrode of the switch tube Q2 is connected to the power control end of the master control module, and the resistor R16 is connected in parallel between the gate electrode and the source electrode of the switch tube Q2; the resistor R9 is connected in parallel between the gate electrode and the source electrode of the switch tube Q1, the gate electrode of the switch tube Q1 is further connected to one anode of the double-end diode D4, the cathode of the diode D4 is grounded through the power switch, the other anode of the double-end diode D4 is connected to the switch detection end of the master control module and one end of the capacitor C9, the other end of the capacitor C9 is grounded; the drain electrode of the switch tube Q1 is connected to the input end of the first voltage conversion unit, and the output end of the first voltage conversion unit is connected to the input end of the second voltage conversion unit; the first voltage conversion unit is used for converting the battery output voltage into 5V voltage, and the second voltage conversion unit is used for converting the 5V voltage into 3.3V voltage.

8. The nondestructive, break-free automotive CAN bus testing device of claim 7, wherein, The display module comprises an OLED display screen.

9. The non-destructive, break-free automotive CAN bus testing device of claim 8, wherein, Further comprising a shell, the inductive signal interface, the CAN signal interface and the OLED display screen are arranged on the surface of the shell, and part of the CAN signal extraction module, the CAN signal conversion module, the master control module and the power module are arranged on the circuit board embedded in the shell.

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