CN218383735U - Differential bus system for automobile diagnosis and automobile diagnosis instrument - Google Patents
Differential bus system for automobile diagnosis and automobile diagnosis instrument Download PDFInfo
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- CN218383735U CN218383735U CN202222970017.2U CN202222970017U CN218383735U CN 218383735 U CN218383735 U CN 218383735U CN 202222970017 U CN202222970017 U CN 202222970017U CN 218383735 U CN218383735 U CN 218383735U
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Abstract
The utility model discloses a differential bus system and automotive diagnostic appearance for automotive diagnosis, it includes master control MCU circuit, adjustable differential bus circuit and OBD diagnosis interface, master control MCU circuit output or receipt square wave pulse, adjustable differential bus circuit includes differential bus high-end transmitting circuit and differential bus low side transmitting circuit, master control MCU circuit parallel connection differential bus high-end transmitting circuit and differential bus low side transmitting circuit, just OBD diagnosis interface is connected respectively to differential bus high-end transmitting circuit and differential bus low side transmitting circuit, and the voltage difference through differential bus high-end transmitting circuit and differential bus low side transmitting circuit changes the simulation and has realized data stream transmission between master control MCU circuit and the OBD diagnosis interface, has finally realized carrying out the function of troubleshooting or diagnosis to the car, and it has solved current automotive diagnostic appearance and can't carry out the diagnostic problem to having adjustable differential bus car, has enlarged diagnostic appearance use scene, has improved diagnostic appearance's commonality.
Description
Technical Field
The utility model relates to an automobile diagnosis technical field especially relates to a differential bus system and automobile diagnosis appearance for automobile diagnosis.
Background
The automobile bus is a channel for data exchange between an automobile ECU and each control unit of an automobile, the current general automobile bus mainly comprises a K line, an RS485 line, an RS232 line, a J1850 line, a single-wire CAN line, a low-speed CAN line, a high-speed CAN line, a CANFD line, an automobile Ethernet and the like, and the automobile bus has the biggest characteristic that stable and reliable data signals CAN be transmitted by using the fewest wire harnesses, and meanwhile, along with the improvement of the technology, the transmission speed is faster and faster, and more information is contained in bus data streams. Because of the various bus forms, the bus forms adopted by various automobile manufacturers are different, and different bus forms can be adopted by different automobile models of the same automobile manufacturer according to the technical characteristics of the same automobile manufacturer. The ECU is used as a control core of an automobile, the data security of the ECU must be guaranteed, and different automobile manufacturers establish a non-standard bus standard, namely an adjustable differential bus, in order to protect automobile ECU data and prevent the ECU data from being illegally rewritten or read.
However, although the way of setting the adjustable differential bus in the automobile prevents the ECU data from being illegally rewritten or read, it has a significant disadvantage that the existing diagnostic device cannot check the automobile with the adjustable differential bus, and once the automobile with the adjustable differential bus fails, the ordinary diagnostic device cannot normally read the state of the ECU from the OBD diagnostic port, which brings inconvenience to the automobile maintenance.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is to provide a differential bus system and automotive diagnostic appearance for automotive diagnosis, it has solved current automotive diagnostic appearance and can't carry out automotive diagnosis's problem to having adjustable differential bus car, has enlarged diagnostic appearance and has used the scene, has improved the commonality of diagnostic appearance to overcome prior art's not enough.
In order to solve the above technical problems, the utility model provides a differential bus system for automobile diagnosis, which comprises a main control MCU circuit, an adjustable differential bus circuit and an OBD diagnosis interface which are connected in sequence,
the master control MCU circuit comprises two paths of IO interfaces, wherein one path of IO interface is an output IO interface for outputting square wave pulses, and the other path of IO interface is an input IO interface for receiving the square wave pulses;
the adjustable differential bus circuit comprises a differential bus high-end transmitting circuit, a differential bus low-end transmitting circuit, a differential bus matching terminal and a differential bus receiving circuit, wherein an output IO interface of the master control MCU circuit is connected with input interfaces of the differential bus high-end transmitting circuit and the differential bus low-end transmitting circuit in parallel, the output interface of the differential bus high-end transmitting circuit and the output interface of the differential bus low-end transmitting circuit are respectively connected with the OBD diagnosis interface, the output interface of the differential bus high-end transmitting circuit and the output interface of the differential bus low-end transmitting circuit are connected with the differential bus matching terminal, the differential bus receiving circuit receives differential signals output by the adjustable differential bus circuit and transmits the differential signals to the input IO interface of the master control MCU circuit, and data stream transmission from the output IO interface of the MCU master control circuit to the OBD diagnosis interface is realized through the adjustable differential bus circuit.
As an improvement of the utility model, differential bus matching terminal includes terminal resistance R5, terminal resistance R5's one end is connected to differential bus high-end transmitting circuit's output interface, and the other end is connected to differential bus low side transmitting circuit's output interface.
As a further improvement of the present invention, the differential bus high-end transmitting circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a triode Q1, a triode Q2, a safety resistor F1 and at least one diode D1, wherein one end of the resistor R2 is connected to an output IO interface of the main control MCU circuit, the other end of the resistor R2 is connected in parallel with one end of the resistor R3 and a base of the triode Q2, and the other end of the resistor R3 is connected in parallel with an emitter of the triode Q2 and one end of the resistor R4 and then connected to a ground GND; the collector of the triode Q2 is connected with one end of the resistor R1, and the other end of the resistor R1 is connected with the base of the triode Q1; an emitting electrode of the triode Q1 is connected with one end of a safety resistor F1, and the other end of the safety resistor F1 is connected to a power input end VCCIN; the collector of the triode Q1 is connected with the other end of the resistor R4 and the anode of the diode D1 in parallel; the cathode of the diode D1 is connected in parallel with one end of the terminal resistor R5, and the cathode of the diode D1 is connected to the output interface of the differential bus high-end sending circuit.
As a further improvement of the present invention, the differential bus low-side transmitting circuit includes a resistor R6, a resistor R7, a transistor Q3, and at least one diode D2, wherein one end of the resistor R6 is connected to an output IO interface of the main control MCU circuit, and the other end of the resistor R6 is connected in parallel with one end of the resistor R7 and a base of the transistor Q3; the other end of the resistor R7 is connected with an emitting electrode of the triode Q3, and meanwhile, the other end of the resistor R7 is connected to a ground end GND in parallel; the collector of the triode Q3 is connected with one end of a resistor R9, and meanwhile, the collector of the triode Q3 is connected to the negative electrode of a diode D2 in parallel; the anode of the diode D2 is connected in parallel with the other end of the termination resistor R5, and the anode of the diode D2 is connected to the output interface of the low-side transmitting circuit of the differential bus.
As a further improvement of the present invention, the differential bus receiving circuit includes a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, and a comparator U1A, wherein one end of the resistor R9 is connected to the cathode of the diode D2, and the other end of the resistor R9 is connected to the 2 nd pin of the comparator U1A; one end of the resistor R11 is connected to a power supply input end VCCIN, and the other end of the resistor R11 is connected with one end of the resistor R12 and the 3 rd pin of the comparator U1A in parallel; the other end of the resistor R12 is connected in parallel with a 4 th pin of the comparator U1A and then connected to a ground end GND, and an 8 th pin of the comparator U1A is connected to a power supply input end VCCIN; one end of the resistor R8 is connected with a power supply VCC3V3, the other end of the resistor R8 is connected with the 1 st pin of the comparator U1A and one end of the resistor R10 in parallel, and the other end of the resistor R10 is connected to an input IO interface of the master control MCU circuit.
In addition the utility model discloses in still disclose an automobile diagnosis appearance, it includes as above-mentioned differential bus system.
After adopting such design, the utility model discloses following advantage has at least:
(1) The utility model discloses a can be used to the adjustable differential bus system in the diagnostic apparatus, make the diagnostic apparatus can carry out troubleshooting or diagnosis to the vehicle that adopts adjustable differential bus through OBD diagnosis interface to make maintenance personal can be quick accurate judgement vehicle state, can high efficiency's detection and maintenance adopt adjustable differential bus circuit's automobile fault and state, bring the convenience for auto repair, improve maintenance efficiency.
(2) The utility model provides an adjustable differential bus circuit has realized the data stream from master control MCU circuit output through the differential signal simulation that differential bus high-end transmitting circuit and differential bus low side transmitting circuit exported to transmit to OBD diagnosis interface by adjustable differential bus circuit, realized the data stream transmission between master control MCU circuit and the OBD diagnosis interface, and then realized carrying out the function of troubleshooting or diagnosis to the car.
Drawings
The foregoing is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention is described in further detail below with reference to the accompanying drawings and the detailed description of the present invention.
Fig. 1 is a schematic structural diagram of a differential bus system for automobile diagnosis according to an embodiment of the present invention.
Fig. 2 is a schematic circuit diagram of a differential bus system according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a differential bus high-side transmission circuit according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a differential bus low-side transmitting circuit according to an embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a differential bus receiving circuit according to an embodiment of the present invention.
Detailed Description
Examples of embodiments described in the present disclosure are illustrated in the accompanying drawings, where like reference numerals refer to the same or similar parts or parts having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, or can be communicated between the two components. The specific meaning of the above terms in the present invention can be understood as specific cases to those skilled in the art.
Referring to fig. 1, a differential bus system for vehicle diagnosis is specifically disclosed in this embodiment, which includes a main control MCU circuit, an adjustable differential bus circuit, and an OBD diagnosis interface, which are connected in sequence. It should be noted that the differential bus system can be applied to an automobile diagnostic apparatus to perform troubleshooting or diagnosis on an automobile with an adjustable differential bus.
Specifically, the main control MCU circuit includes two paths of IO interfaces, one of the IO interfaces is an output IO interface for outputting square wave pulses, and the other of the IO interfaces is an input IO interface for receiving square wave pulses. And two paths of IO interfaces in the main control MCU circuit are used for data transmission and data reception.
As shown in fig. 2 and fig. 3, the adjustable differential bus circuit includes a differential bus high-end transmitting circuit, a differential bus low-end transmitting circuit, a differential bus matching terminal, and a differential bus receiving circuit, where the adjustable differential bus circuit is mainly used to convert pulses sent by the main control MCU circuit into a high-end pulse signal and a low-end pulse signal, so as to form a differential signal form, and the adjustable differential bus circuit is connected to the OBD diagnostic interface and sends a data stream for diagnosis to the OBD diagnostic interface in a differential signal manner. Meanwhile, the adjustable differential bus circuit also inputs the differential signal data stream in the adjustable differential bus circuit into the master control MCU circuit through the differential bus receiving circuit for diagnosis of the vehicle.
Wherein the output IO interface parallel connection difference bus high-end transmitting circuit of master control MCU circuit and the input interface of difference bus low side transmitting circuit, the output interface of difference bus high-end transmitting circuit and the output interface of difference bus low side transmitting circuit connect respectively OBD diagnoses the interface, just connect between the output interface of difference bus high-end transmitting circuit and the output interface of difference bus low side transmitting circuit difference bus matching terminal, difference bus receiving circuit receives the difference signal of adjustable difference bus circuit output and transmits to the input IO interface of master control MCU circuit.
When the main control MCU circuit has no data output, the voltage of the output interface of the differential bus high-end transmitting circuit and the voltage of the output interface of the differential bus low-end transmitting circuit are equal, the voltage difference is 0, and the voltage difference on the adjustable differential bus circuit represents the binary number 0 in the data stream; when the master control MCU circuit outputs data, a voltage difference V exists between the output interface of the differential bus high-end transmitting circuit and the output interface of the differential bus low-end transmitting circuit, the voltage difference V on the adjustable differential bus circuit represents binary number 1 in the data stream, and the binary data in the data stream is simulated through the voltage difference of the adjustable differential bus circuit, so that the data stream transmission from the output IO interface of the master control MCU circuit to the OBD diagnosis interface is realized.
The differential bus matching terminal comprises a terminal resistor R5, one end of the terminal resistor R5 is connected to an output interface of the differential bus high-end transmitting circuit, the other end of the terminal resistor R5 is connected to an output interface of the differential bus low-end transmitting circuit, and the terminal resistor R5 is used for improving the transmission waveform of differential signals and reducing high-speed signal reflection. The value of the termination resistor R5 in this embodiment is preferably 100 ohms.
As shown in fig. 4, the differential bus high-end transmitting circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a triode Q1, a triode Q2, a safety resistor F1, and at least one diode D1, in this embodiment, preferably, the resistor R1 and the resistor R2 take 4.7 kohms, the resistor R3 takes 10 kohms, the resistor R4 takes 1 kohms, the triode Q1 uses MMBT3906, the triode Q2 uses MMBT3904W, the diode D1 uses SS14, and the safety resistor F1 uses parameters of 0.1A/60.
Specifically, one end of the resistor R2 is connected to an output IO interface of the main control MCU circuit, the other end of the resistor R2 is connected in parallel with one end of the resistor R3 and a base of the transistor Q2, and the other end of the resistor R3 is connected in parallel with an emitter of the transistor Q2 and one end of the resistor R4 and then connected to a ground GND; the collector of the triode Q2 is connected with one end of the resistor R1, and the other end of the resistor R1 is connected with the base of the triode Q1; an emitting electrode of the triode Q1 is connected with one end of a safety resistor F1, and the other end of the safety resistor F1 is connected to a power input end VCCIN; the collector of the triode Q1 is connected in parallel with the other end of the resistor R4 and the anode of the diode D1; the cathode of the diode D1 is connected in parallel with one end of the terminal resistor R5, and the cathode of the diode D1 is connected to the output interface OUT-P of the differential bus high-end sending circuit.
The working process of the differential bus high-end sending circuit is as follows:
when the output IO interface of the main control MCU circuit outputs a low level, after voltage division is performed by the resistors R2 and R3, the voltage applied to the base of the transistor Q2 is a low level, at this time, the transistor Q2 is turned off, the transistor Q2 is in an open circuit state, and at the same time, the transistor Q1 is in an open circuit state, the anode of the diode D1 is a zero level, at this time, the diode D1 is in a reverse cut-off state, because the voltage of the output interface in the differential bus high-end transmitting circuit is in a static state, the voltage thereof is maintained at a constant value, in this embodiment, the voltage of the output interface in the differential bus high-end transmitting circuit is set to be V _ OUT, that is, the voltage of the output interface in the differential bus high-end transmitting circuit is V _ OUT. It should be noted that the actual voltage of V _ OUT is related to the vehicle type, based on the measured value of the vehicle.
When the output IO interface of the main control MCU circuit outputs high level, after voltage division is carried OUT through the resistor R2 and the resistor R3, the voltage added to the base electrode of the triode Q2 is high level, the base electrode of the triode Q2 is conducted in forward bias mode, the collector electrode level of the triode Q2 is basically equal to the ground end GND, the base electrode of the triode Q1 is low level, the triode Q1 is in a conducting state, the collector electrode voltage of the triode Q1 is basically equal to the power input end VCCIN, the diode D1 is conducted in forward direction because the power input end VCCIN is larger than V _ OUT, the diode D1 is in forward direction, the cathode voltage of the diode D1 is VCCIN-P because the forward voltage drop of the diode D1 is a constant value P, and the voltage of the output interface in the differential bus high-end sending circuit is increased to be VCCIN-P at the moment. For example, if the forward voltage drop of the diode D1 is a constant value of 0.3V, the voltage of the cathode of the diode D1 is VCCIN-0.3V after the power input terminal VCCIN passes through the diode D1, and since VCCIN-0.3V is much larger than V _ OUT, the voltage of the output interface in the high-side transmitting circuit of the differential bus will be increased to VCCIN-0.3V.
Referring to fig. 5, the differential bus low-side transmitting circuit in this embodiment includes a resistor R6, a resistor R7, a transistor Q3, and at least one diode D2. In this embodiment, it is preferable that the resistor R6 has a value of 4.7 kohm, the resistor R7 has a value of 10 kohm, the triode Q3 is MMBT3904W, and the diode D2 is SS14.
Specifically, one end of the resistor R6 is connected to an output IO interface of the main control MCU circuit, and the other end of the resistor R6 is connected in parallel with one end of the resistor R7 and the base of the triode Q3; the other end of the resistor R7 is connected with an emitting electrode of the triode Q3, and the other end of the resistor R7 is connected to a ground end GND in parallel; the collector of the triode Q3 is connected with one end of a resistor R9, and meanwhile, the collector of the triode Q3 is connected to the negative electrode of a diode D2 in parallel; the anode of the diode D2 is connected in parallel with the other end of the termination resistor R5, and the anode of the diode D2 is connected to the output interface OUT-N of the low-side transmitting circuit of the differential bus.
The working process of the differential bus low-end transmitting circuit is as follows:
when the output IO interface of the main control MCU circuit outputs a low level, after voltage division is performed by the resistor R6 and the resistor R7, the voltage applied to the base of the transistor Q3 is a low level, at this time, the transistor Q3 is turned off, and the transistor Q3 is in an open circuit state, so that the cathode of the diode D2 is in an open circuit state, since the levels of the output interfaces of the differential bus high-side transmitting circuit and the differential bus low-side transmitting circuit of the adjustable differential bus circuit in a static state are kept equal, the voltage of the output interface in the differential bus high-side transmitting circuit is V _ OUT, and the voltage difference between the differential bus high-side transmitting circuit and the differential bus low-side transmitting circuit in the adjustable differential bus circuit is 0. It should be noted that the actual voltage of V _ OUT is related to the vehicle type, based on the measured value of the vehicle.
When the output IO interface of the main control MCU circuit outputs high level, after voltage division is carried out through the resistor R6 and the resistor R7, the voltage added to the base electrode of the triode Q3 is high level, the forward bias of the triode Q3 is conducted at the moment, the voltage of the collector electrode of the triode Q3 is equal to the ground end GND, namely the voltage of the cathode of the diode D2 is equal to the ground end GND at the moment, the forward voltage drop of the single diode D2 is a constant value P, so that the voltage is pulled down to P through the anode of the diode D2, and finally the voltage of the output interface in the low-end transmitting circuit of the differential bus is pulled down to P.
In this embodiment, when the master control MCU circuit has no data transmission, that is, the output IO interface of the master control MCU circuit outputs a low level, the voltages of the output interfaces of the differential bus high-side transmitting circuit and the differential bus low-side transmitting circuit are both V _ OUT, the voltage difference on the adjustable differential bus circuit is 0, and the voltage difference represents a binary number 0 in the data stream; when the master control MCU circuit transmits data, namely the output IO interface of the master control MCU circuit outputs high level, the voltage of the output interface of the low-end transmitting circuit of the differential bus is VCCIN-P, and the voltage of the output interface of the low-end transmitting circuit of the differential bus is P, therefore, the voltage difference V between the voltage of the high-end differential bus and the voltage of the low-end differential bus is = VCCIN-2P, the voltage difference V on the adjustable differential bus circuit represents binary number 1 in data stream, and the data transmission process from the output IO interface of the master control MCU circuit to the OBD diagnosis interface is realized through the voltage difference change of the adjustable differential bus circuit.
Further, referring to fig. 6, the differential bus receiving circuit in this embodiment includes a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, and a comparator U1A. In this embodiment, preferably, the resistor R8 is 4.7K ohms, the resistor R9 is 10K ohms, the resistor R10 is 1K ohms, and the resistance values of the resistor R11 and the resistor R12 are according to the following formula:
R12÷(R11+R12)xVCCIN＝V_OUT/2；
according to the above formula, the values of the resistor R11 and the resistor R12 are taken, so that after voltage division is performed by the resistor R12 and the resistor R11, the voltage of the 3 rd pin of the comparator U1A is equal to a half of the output interface voltage of the differential bus high-end transmitting circuit or the differential bus low-end transmitting circuit in the static state, in this embodiment, the resistor R11 preferably selects an 18K resistor, and the resistor R12 preferably selects a 2K resistor.
Specifically, one end of the resistor R9 is connected to the cathode of the diode D2, and the other end of the resistor R9 is connected to the 2 nd pin of the comparator U1A; one end of the resistor R11 is connected to a power supply input end VCCIN, and the other end of the resistor R11 is connected with one end of the resistor R12 and the 3 rd pin of the comparator U1A in parallel; the other end of the resistor R12 is connected in parallel with a 4 th pin of the comparator U1A and then connected to a ground end GND, and an 8 th pin of the comparator U1A is connected to a power supply input end VCCIN; one end of the resistor R8 is connected with a power supply VCC3V3, the other end of the resistor R8 is connected with the 1 st pin of the comparator U1A and one end of the resistor R10 in parallel, and the other end of the resistor R10 is connected to an input IO interface of the master control MCU circuit. The differential bus receiving circuit is mainly used for receiving differential signal data streams transmitted by the adjustable differential bus circuit and transmitting the differential signal data streams to the main control MCU circuit, so that the diagnostic apparatus can perform automobile fault analysis according to the differential signal data streams.
The working process of the differential bus receiving circuit is as follows:
when the design is carried OUT, a voltage value V _ OUT/2 is obtained by dividing the voltage of a resistor R12 and a resistor R11, so that the voltage of a 3 rd pin of an integrated comparator U1A is also V _ OUT/2, when binary data transmitted by an adjustable differential bus circuit is 1, a triode Q3 in a low-end transmitting circuit of a differential bus is in a conducting state, the voltage of a cathode of a diode D2 in the low-end transmitting circuit of the differential bus is P, the voltage of a cathode of the diode D2 is loaded to a 2 nd pin of the comparator U1A through a resistor R9, and because the voltage of the 3 rd pin of the comparator U1A is greater than the voltage of the 2 nd pin of the comparator U1A, the 1 st pin of the comparator U1A outputs a high level and is connected to an input IO interface of a master control MCU circuit through a resistor R10, so that the IO interface of the master control MCU circuit is a high level, the input interface of the master control MCU circuit receives the binary data 1;
when the binary data transmitted by the adjustable differential bus circuit is 0, the triode Q3 in the differential bus low-side transmitting circuit is in a cut-off state, at this time, the cathode voltage of the diode D2 of the differential bus low-side transmitting circuit is equal to the voltage V _ OUT of the output interface of the differential bus low-side transmitting circuit, the cathode voltage of the diode D2 is loaded to the 2 nd pin of the comparator U1A through the resistor R9, at this time, the 3 rd pin voltage of the comparator U1A is smaller than the 2 nd pin voltage of the comparator U1A, so that the 1 st pin of the comparator U1A outputs a low level and is connected to the input interface of the main control MCU circuit through the resistor IO 10, the input IO interface of the main control MCU circuit is a low level, and then the input IO interface of the main control MCU circuit receives the binary data 0.
The above description is only for the preferred embodiment of the present invention, and not intended to limit the present invention in any way, and those skilled in the art can make various modifications, equivalent changes and modifications using the above-described technical content, all of which fall within the scope of the present invention.
Claims (7)
1. A differential bus system for automobile diagnosis is characterized by comprising a main control MCU circuit, an adjustable differential bus circuit and an OBD diagnosis interface which are connected in sequence,
the main control MCU circuit comprises two paths of IO interfaces, wherein one path of IO interface is an output IO interface for outputting square wave pulse, and the other path of IO interface is an input IO interface for receiving square wave pulse;
the adjustable differential bus circuit comprises a differential bus high-end transmitting circuit, a differential bus low-end transmitting circuit and a differential bus matching terminal, wherein an output IO interface of the master control MCU circuit is connected with an input interface of the differential bus high-end transmitting circuit and the differential bus low-end transmitting circuit in parallel, the output interface of the differential bus high-end transmitting circuit and the output interface of the differential bus low-end transmitting circuit are respectively connected with the OBD diagnosis interface, the output interface of the differential bus high-end transmitting circuit and the output interface of the differential bus low-end transmitting circuit are connected with the differential bus matching terminal, and data stream transmission from the output IO interface of the master control MCU circuit to the OBD diagnosis interface is realized through the adjustable differential bus circuit.
2. The differential bus system of claim 1, wherein the adjustable differential bus circuit further comprises a differential bus receiving circuit, and the differential bus receiving circuit receives the differential signal output by the adjustable differential bus circuit and transmits the differential signal to an input IO interface of the master MCU circuit.
3. The differential bus system as recited in claim 1 wherein the differential bus match terminal comprises a termination resistor R5, wherein one end of the termination resistor R5 is connected to the output interface of the differential bus high-side transmitter circuit, and the other end is connected to the output interface of the differential bus low-side transmitter circuit.
4. The differential bus system according to claim 3, wherein the differential bus high-side transmitting circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a transistor Q1, a transistor Q2, a safety resistor F1 and at least one diode D1, wherein one end of the resistor R2 is connected to an output IO interface of the main control MCU circuit, the other end of the resistor R2 is connected in parallel with one end of the resistor R3 and a base of the transistor Q2, and the other end of the resistor R3 is connected in parallel with an emitter of the transistor Q2 and one end of the resistor R4 and then connected to a ground GND; the collector of the triode Q2 is connected with one end of the resistor R1, and the other end of the resistor R1 is connected with the base of the triode Q1; an emitting electrode of the triode Q1 is connected with one end of a safety resistor F1, and the other end of the safety resistor F1 is connected to a power input end VCCIN; the collector of the triode Q1 is connected with the other end of the resistor R4 and the anode of the diode D1 in parallel; the cathode of the diode D1 is connected in parallel with one end of the terminal resistor R5, and the cathode of the diode D1 is connected to the output interface of the differential bus high-end sending circuit.
5. The differential bus system according to claim 4, wherein the differential bus low-side transmitting circuit comprises a resistor R6, a resistor R7, a transistor Q3 and at least one diode D2, wherein one end of the resistor R6 is connected to an output IO interface of the main control MCU circuit, and the other end of the resistor R6 is connected in parallel with one end of the resistor R7 and a base of the transistor Q3; the other end of the resistor R7 is connected with an emitting electrode of the triode Q3, and the other end of the resistor R7 is connected to a ground end GND in parallel; the collector of the triode Q3 is connected with one end of the resistor R9, and the collector of the triode Q3 is connected to the negative electrode of the diode D2 in parallel; the anode of the diode D2 is connected in parallel with the other end of the termination resistor R5, and the anode of the diode D2 is connected to the output interface of the low-side transmitting circuit of the differential bus.
6. The differential bus system as claimed in claim 5, wherein the differential bus receiving circuit comprises a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12 and a comparator U1A, wherein one end of the resistor R9 is connected to the cathode of the diode D2, and the other end of the resistor R9 is connected to the 2 nd pin of the comparator U1A; one end of the resistor R11 is connected to a power supply input end VCCIN, and the other end of the resistor R11 is connected with one end of the resistor R12 and the 3 rd pin of the comparator U1A in parallel; the other end of the resistor R12 is connected in parallel with a 4 th pin of the comparator U1A and then connected to a ground end GND, and an 8 th pin of the comparator U1A is connected to a power supply input end VCCIN; one end of the resistor R8 is connected with a power supply VCC3V3, the other end of the resistor R8 is connected with the 1 st pin of the comparator U1A and one end of the resistor R10 in parallel, and the other end of the resistor R10 is connected to an input IO interface of the master control MCU circuit.
7. An automotive diagnostic apparatus comprising a differential bus system as claimed in any one of claims 1 to 6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222970017.2U CN218383735U (en) | 2022-11-08 | 2022-11-08 | Differential bus system for automobile diagnosis and automobile diagnosis instrument |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222970017.2U CN218383735U (en) | 2022-11-08 | 2022-11-08 | Differential bus system for automobile diagnosis and automobile diagnosis instrument |
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| Publication Number | Publication Date |
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| CN218383735U true CN218383735U (en) | 2023-01-24 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202222970017.2U Active CN218383735U (en) | 2022-11-08 | 2022-11-08 | Differential bus system for automobile diagnosis and automobile diagnosis instrument |
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| Country | Link |
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| CN (1) | CN218383735U (en) |
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- 2022-11-08 CN CN202222970017.2U patent/CN218383735U/en active Active
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