A vehicle bus level detection device

Abstract

The present invention discloses a vehicle bus level detection device, which belongs to the field of electronics, and comprises an OBD port bus selection network circuit, a signal adjustment circuit and an output circuit connected in sequence, wherein: one end of the OBD port bus selection network circuit is used to connect various diagnostic ports in the vehicle OBD interface, and receive the level signal sent by the vehicle OBD diagnostic port, and the OBD port bus selection network circuit is also used to connect with the IO port line of the MCU to control the selection of the OBD port pin; the signal adjustment circuit is connected to the other end of the OBD port bus selection network circuit, and is used to adjust the line level of the vehicle end to the signal level range that the MCU can recognize, and send the adjusted level signal to the output circuit, and the output end of the output circuit is used to connect with the AD conversion port of the MCU. The present invention can enable vehicle maintenance personnel to quickly and accurately understand the bus distribution of the OBD port, so as to quickly and accurately judge the level and waveform of each pin of the vehicle OBD, and improve maintenance efficiency.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, and in particular to a vehicle bus level detection device. Background Art

[0002] With the rapid development of domestic and commercial vehicles in my country, the automobile maintenance industry is also developing continuously. The problem that comes with it is how to quickly and accurately determine the fault after the vehicle breaks down. For this reason, the market urgently needs some professional detection and maintenance equipment to improve the maintenance speed and quality.

[0003] The automobile OBD diagnostic port provides a channel for detecting vehicle ECU information. Currently, the common bus forms of automobiles include CAN line, PWM / VPWM, K-Line, S232, RS485, TTL and other buses. Different models may use one or a combination of these buses, and the definition of the buses on the OBD pins of different models is also different. If the maintenance personnel are asked to manually test and troubleshoot each pin, it will waste a lot of time. Therefore, it is necessary to propose an automobile bus level detection device that can quickly and accurately determine the level and waveform of each pin of the vehicle OBD to improve the maintenance speed and quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an automobile bus level detection device which can quickly and accurately judge the level and waveform of each pin of the vehicle OBD.

[0005] In order to solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0006] In one aspect, the present invention provides a vehicle bus level detection device, comprising a vehicle OBD port bus selection network circuit, a signal adjustment circuit and an output circuit connected in sequence, wherein:

[0007] One end of the OBD port bus selection network circuit is used to connect to the diagnostic port in each port of the automobile OBD and receive the level signal sent by the automobile OBD diagnostic port. The OBD port bus selection network circuit is also used to connect to the IO port line of the MCU to control the selection of the OBD port pin;

[0008] The signal adjustment circuit is connected to the other end of the OBD port bus selection network circuit, and is used to adjust the line level of the car end to the signal level range that the MCU can recognize, and send the adjusted level signal to the output circuit. The output end of the output circuit is used to connect to the AD conversion port of the MCU.

[0009] Furthermore, the automobile OBD port bus selection network circuit includes a driver and a relay connected to the output port of the driver, the common end of the relay is used to connect to the automobile OBD diagnostic port, and the normally open contact of the relay is used to select an input signal for the signal adjustment circuit.

[0010] Further, the driver includes a first driver, a second driver and a third driver, the number of the relays includes sixteen, namely the first relay to the sixteenth relay, the normally open contacts of the sixteen relays are connected together as a bus input signal, the normally closed contacts of the sixteen relays are suspended, and the common ends of the sixteen relays are respectively used to connect to each automobile OBD diagnostic port, wherein:

[0011] The 7 input ports of the first driver are respectively used to connect the IO1 port line to the IO7 port line of the MCU, and correspondingly, the 7 output ports of the first driver are respectively connected to the negative power terminals of the coil control pins of the first to seventh relays, and the positive power terminals of the coil control pins are connected to VCC;

[0012] The 7 input ports of the second driver are respectively used to connect the IO8 port line to the IO14 port line of the MCU, and correspondingly, the 7 output ports of the second driver are respectively connected to the negative power terminals of the coil control pins of the eighth relay to the fourteenth relay, and the positive power terminals of the coil control pins are connected to VCC;

[0013] The two input ports of the third driver are respectively used to connect to the IO15 line and the IO16 line of the MCU. Correspondingly, the two output ports of the third driver are respectively connected to the negative power terminals of the coil control pins of the fifteenth relay and the sixteenth relay, and the positive power terminals of the coil control pins are connected to VCC.

[0014] Furthermore, the driver is a high-current transistor array driver.

[0015] Furthermore, the signal adjustment circuit includes a voltage-dividing resistor network circuit, an ESD protection circuit and a high-frequency interference signal filtering circuit, which are used for voltage-dividing adjustment of the level signal, transient high voltage suppression and interference filtering.

[0016] Further, the signal adjustment circuit includes a first resistor, a second resistor, a third resistor, a first diode, and a fourth capacitor, wherein:

[0017] The bus port, the first resistor, the second resistor and the output circuit of the automobile OBD port bus selection network circuit are connected in sequence;

[0018] One end of the first diode is connected between the first resistor and the second resistor, and the other end of the first diode is used to be connected to the ground to limit the surge of the instantaneous high voltage signal;

[0019] The fourth capacitor is connected in parallel with the third resistor, one end of the fourth capacitor is connected to one end of the third resistor and then connected to the ground, and the other end of the fourth capacitor is connected to the other end of the third resistor and then connected between the second resistor and the output circuit.

[0020] Furthermore, the first diode is a bidirectional TVS diode with a maximum breakdown voltage of 34V.

[0021] Further, the resistance value of the first resistor is selected as 90.9K_1%, the resistance value of the second resistor R2 is selected as 9.1K_1%, and the resistance value of the third resistor R3 is selected as 10K_1%.

[0022] Furthermore, the fourth capacitor is a ceramic chip capacitor.

[0023] Furthermore, the output circuit includes a precision operational amplifier and a fourth resistor connected in sequence, the precision operational amplifier is connected to the signal adjustment circuit, and the fourth resistor is the output end of the output circuit for connecting to the AD conversion port of the MCU.

[0024] Furthermore, the positive input terminal of the precision operational amplifier is connected to the signal adjustment circuit, the negative input terminal of the precision operational amplifier is connected to the output terminal of the precision operational amplifier and then connected to one end of a fourth resistor, and the other end of the fourth resistor is used to be connected to the AD conversion port of the MCU.

[0025] Furthermore, it also includes an MCU, and the MCU includes an IO port line and an AD conversion port.

[0026] After adopting such a design, the present invention has at least the following advantages:

[0027] One end of the automobile OBD port bus selection network of the present invention is connected to each port of the automobile OBD to receive the voltage signal sent by the automobile OBD diagnostic port, and the relay network is sequentially selected by the driver to achieve the purpose of selecting the OBD port pin. The signal adjustment circuit is used to convert the line level of the automobile end into a signal level range that the MCU can recognize, and send the conditioned signal to the output circuit connected to the other end of the signal adjustment circuit; the output end of the output circuit is used to connect the AD conversion input port of the MCU to realize the acquisition of the signal level, and the output circuit is used to isolate the signal adjustment circuit from the MCU circuit and stabilize the signal of the signal adjustment circuit, so as to avoid the influence of the AD input circuit of the MCU on the signal adjustment circuit, so that the detected bus signal level is relatively stable. The present invention collects the level of each pin through the high-performance MCU, and can accurately determine the bus type according to the level value of each pin, so that the vehicle maintenance personnel can quickly and accurately understand the bus distribution of the OBD port, thereby quickly and accurately judging the level and waveform of each pin of the vehicle OBD, providing great help for vehicle fault diagnosis and improving maintenance efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0029] Figure 1 It is a connection diagram of the automobile bus level detection device of the present invention;

[0030] Figure 2 The present invention is a circuit diagram of a vehicle bus level detection device. DETAILED DESCRIPTION

[0031] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0032] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0033] Those skilled in the art will appreciate that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined.

[0034] The present invention provides an embodiment of a vehicle bus level detection device, such as Figure 1 , Figure 2 As shown, it includes an OBD port bus selection network circuit, a signal adjustment circuit and an output circuit connected in sequence, wherein: one end of the OBD port bus selection network circuit is used to connect to the diagnostic port among the automobile OBD ports and receive the level signal sent by the automobile OBD diagnostic port, and the OBD port bus selection network circuit is also used to connect to the IO port line of the MCU to control the selection of the OBD port pin; the signal adjustment circuit is connected to the other end of the OBD port bus selection network circuit, and is used to adjust the line level of the automobile end to the signal level range that the MCU can recognize, and send the adjusted level signal to the output circuit, and the output end of the output circuit is used to connect to the AD conversion port of the MCU.

[0035] One end of the automobile OBD port bus selection network of the present invention is connected to each automobile OBD diagnostic port, and is controlled by the IO port of the MCU to receive the voltage signal of each port line of the automobile OBD port. The signal adjustment circuit is used for voltage division adjustment of the signal level, filtering out the input interference signal, limiting the transient high voltage surge, and sending the adjusted voltage signal to the output circuit connected to the signal adjustment circuit; the other end of the output circuit is used to connect to the AD conversion port of the MCU to output a stable and required voltage signal.

[0036] That is to say, the OBDPIN terminal of the automobile OBD port bus selection network is the input terminal of the present invention, which is used to connect the various endpoints of the automobile OBD port. The ADC_IN terminal of the output circuit is the output terminal of the present invention, which is used to connect the AD conversion port of the MCU and send the voltage signal to the MCU to realize the collection of the signals of each endpoint.

[0037] In one embodiment, Figure 2As shown, the automobile OBD port bus selection network circuit includes a first driver U1, a second driver U2, and a third driver U3. These three drivers have a total of sixteen output terminals (pins O1 to O16), which are respectively connected to the negative power supply terminals of the coil control pins (pins OBD_SEL1 to OBD_SEL16) of the sixteen relays (K1 to K16), and the positive power supply terminals of the coil control pins are connected to VCC. The input terminals (I1 to I7) of the three drivers are respectively connected to the IO port lines of the MCU (as shown in Figure IO1 to IO16). The signal voltages of the sixteen OBD ports are respectively connected to the common terminals (OBDPIN1 to OBDPIN16) of the sixteen relays (K1 to K16), and the normally open points of the sixteen relays (K1 to K16) are connected together as bus input signals, and the normally closed points of the sixteen relays (K1 to K16) are suspended.

[0038] The present invention realizes that multiple signals share one signal acquisition circuit, which can reduce equipment costs. The MCU outputs high levels in sequence through the IO port in a designed order. After being inverted by the driver, the corresponding relay is attracted to select one of the corresponding OBD sixteen pins to achieve the purpose of selecting the automobile level signal to be input into the signal adjustment circuit.

[0039] In one embodiment, the voltage divider circuit of the signal adjustment circuit is composed of a first precision resistor R1, a second precision resistor R2, a fourth capacitor C4, a third precision resistor R3, and a first diode D1. In one embodiment, one end of the first precision resistor R1 is connected to the OBD bus port selection network, and the other end is connected in parallel with the second precision resistor R2 and one end of the first diode D1, and the other end of the first diode D1 is directly connected to the ground. The other end of the second precision resistor R2 is also connected in parallel with the fourth capacitor C4 and one end of the third resistor R3 to the output circuit. The other end of the fourth capacitor C4 is connected to the other end of the third resistor R3 in parallel and then connected to the ground. Preferably, the parameter value of the first diode is selected as a bidirectional TVS tube SMAJ28CA, with a maximum breakdown voltage of 34V, which can effectively protect the subsequent circuit. Preferably, as shown in Table 1, the resistance value of the first resistor is selected as 90.9K_1%, the resistance value of the second resistor R2 is selected as 9.1K_1%, and the resistance value of the third resistor R3 is selected as 10K_1%. In this way, the voltage division coefficient of R1, R2, and R3 is 0.0909. When the DC level of the OBD bus port changes between 8 and 34V, the voltage level after voltage division is 0.0909x(8-34)=0.72-3.09V, and the input voltage is adjusted to the AD conversion level range of the MCU, which can be correctly collected by the MCU. Based on experience, the fourth capacitor value is preferably a ceramic chip capacitor of 104.

[0040] Table 1 Adjustment circuit values ​​of resistors, capacitors and diodes

[0041] Components Value The first resistor R1 90.9KΩ 1% The second resistor R2 9.1KΩ 1% The third resistor R3 10KΩ 1% The first diode D1 TVS tube SMAJ28CA The fourth capacitor C4 100nf / 50V

[0042] In one embodiment, the first diode after the first resistor R1 of the signal adjustment circuit is a TVS transient suppression diode, which can prevent the influence of external instantaneous high voltage or static electricity on the subsequent circuit. The function of the TVS diode D1 is to limit the level of the transient high voltage signal entering the signal adjustment circuit to between 0 and 34 V. In one embodiment, the TVS is composed of a parallel diode D1, the first resistor R1 and the second resistor R2 are connected in parallel and connected to one end of D1, and the other end of the first diode is grounded.

[0043] In one embodiment, one end of the second resistor R2 of the signal adjustment circuit is connected in parallel with the third resistor R3 and the positive input end of the output circuit operational amplifier, and then connected in parallel with one end of the fourth capacitor C4 for anti-interference signal filtering. The other end of C4 is grounded to provide a stable level in microseconds for the subsequent AD conversion interface for MCU collection.

[0044] In one embodiment, the signal adjustment circuit adjusts the signal level to a level of 0 to 3.3 V and then the signal enters the output circuit. The output circuit is composed of a first operational amplifier U4 and a fourth resistor R4. The signal of the signal adjustment circuit is input to the positive input terminal (pin 3) of the first operational amplifier U4. The negative input terminal (pin 2) of the first operational amplifier U4 is connected to the output terminal (pin 1) of the first operational amplifier U4 and is connected in parallel to one end of the fourth resistor R4. The other end of the fourth resistor R4 is connected to the AD conversion input terminal ADC_IN port of the MCU to realize the collection of the signal level.

[0045] The output circuit reduces the influence of the signal acquisition circuit of the MCU on the signal adjustment circuit, so that the signal level output by the adjustment circuit is not affected by other circuits, and the AD conversion acquisition signal of the MCU is kept relatively stable.

[0046] The specific working process of the automobile bus level detection device of the present invention is as follows:

[0047] First, connect the car OBD port to the OBDPIN1~OBDPIN16 interface of the car bus level detection device, and input the car bus level to the OBDPIN1~OBDPIN16 end of the car OBD port bus selection network of the device; connect the ADC_IN end of the device to the AD conversion input port of the MCU. Output a high-level control signal through the IO port of the MCU to control the IO1~IO16 of the car OBD port bus selection network, and the 16 output ports O1~O16 of the first driver U1, the second driver U2, and the third driver U3 output low levels. O1~O16 are respectively connected to the negative power supply end of the coil control pins (pins OBD_SEL1~OBD_SEL16) of the 16 relays K1~K16, and the positive power supply end of the coil control pin is connected to VCC, so that the corresponding relay will be attracted.

[0048] The OBDPIN1~OBDPIN16 interfaces are connected to the common terminals of 16 relays, and the signal levels of the 16 OBD ports enter the signal adjustment circuit through the common terminals and normally open contacts of the relays.

[0049] The signal passes through the first resistor R1, the second resistor R2, the third resistor R3, the first diode D1, and the fourth capacitor C4. According to industry experience, the first resistor R1 is 90.9K (accuracy 1%), the second resistor R2 is 9.1K (accuracy 1%), and the third resistor R3 is 10K (accuracy 1%). The voltage division coefficient is 10 / (90.9+9.1+10)=0.0909. When the DC level of the OBD bus port changes between 8 and 34V, the voltage level after voltage division is 0.0909x(8~34)=0.72~3.09V. The input voltage is adjusted to the AD conversion level range of the MCU and can be correctly collected by the MCU. Preferably, the diode D1 is a TVS tube with a model of SMAJ28CA, which can suppress the input high-voltage static electricity and play a protective role.

[0050] After passing through the signal adjustment circuit, the vehicle bus level signal is limited to between 0.72 and 3.09V, and the signal enters the third pin of the first precision operational amplifier U4. The second pin and the first pin of the first precision operational amplifier U4 are connected together to form a voltage follower, so that the level of the first pin of the first precision operational amplifier U4 is approximately equal to the voltage of the third pin of U4.

[0051] The bus level signal output from the first pin of the first precision operational amplifier U4 is output to the ADC_IN terminal through R4. R4 acts as a current limiting protection isolation to isolate the ADC_IN terminal from the first pin of U4, so that the circuit at the ADC_IN output terminal has the least impact on U4.

[0052] The device of the present invention is mainly used for selecting the bus selection network in sequence through the OBD port bus, the bus level signal is sent to the signal adjustment circuit for adjustment, and then the bus signal level is input to the AD conversion interface of the MCU through the isolated output of the voltage follower of the output circuit, so as to realize the collection of the bus level signal. The MCU displays the collected signal level and waveform in real time, which provides help for automobile maintenance personnel to quickly judge the fault, greatly facilitates maintenance, and is also one of the necessary tools for a large number of automobile maintenance personnel.

[0053] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art may make some simple modifications, equivalent changes or modifications using the technical contents disclosed above, which all fall within the protection scope of the present invention.

Claims

1. A vehicle bus level detection device, characterized in that: It includes an OBD port bus selection network circuit, a signal adjustment circuit and an output circuit connected in sequence, wherein: One end of the OBD port bus selection network circuit is used to connect to each diagnostic port in the automobile OBD interface and receive the level signal sent by the automobile OBD diagnostic port. The OBD port bus selection network circuit is also used to connect to the IO port line of the MCU to control the selection of the OBD port pin; The signal adjustment circuit is connected to the other end of the OBD port bus selection network circuit, and is used to adjust the line level of the vehicle end to a signal level range that can be recognized by the MCU, and send the adjusted level signal to the output circuit, and the output end of the output circuit is used to connect to the AD conversion port of the MCU; The OBD port bus selection network circuit includes a driver and a relay connected to the output port of the driver, the common end of the relay is used to connect to the OBD diagnostic port of the vehicle, and the normally open contact of the relay is used to select an input signal for the signal adjustment circuit; The driver includes a first driver, a second driver and a third driver. The number of the relays includes sixteen, namely, the first relay to the sixteenth relay. The normally open contacts of the sixteen relays are connected together as a bus input signal. The normally closed contacts of the sixteen relays are suspended. The common ends of the sixteen relays are respectively used to connect to the OBD diagnostic ports of each vehicle, wherein: The 7 input ports of the first driver are respectively used to connect the IO1 port line to the IO7 port line of the MCU, and correspondingly, the 7 output ports of the first driver are respectively connected to the negative power terminals of the coil control pins of the first to seventh relays, and the positive power terminals of the coil control pins are connected to VCC; The 7 input ports of the second driver are respectively used to connect the IO8 port line to the IO14 port line of the MCU, and correspondingly, the 7 output ports of the second driver are respectively connected to the negative power terminals of the coil control pins of the eighth relay to the fourteenth relay, and the positive power terminals of the coil control pins are connected to VCC; The two input ports of the third driver are respectively used to connect to the IO15 port line and the IO16 port line of the MCU. Correspondingly, the two output ports of the third driver are respectively connected to the negative power supply terminals of the coil control pins of the fifteenth relay and the sixteenth relay, and the positive power supply terminals of the coil control pins are connected to VCC. The driver is a high current transistor array driver.

2. The vehicle bus level detection device according to claim 1, characterized in that: The signal adjustment circuit includes a voltage-dividing resistor network circuit, an ESD protection circuit and a high-frequency interference signal filtering circuit, and is used for voltage-dividing adjustment of level signals, transient high voltage suppression and interference filtering.

3. The vehicle bus level detection device according to claim 1, characterized in that: The signal adjustment circuit includes a first resistor, a second resistor, a third resistor, a first diode, and a fourth capacitor, wherein: The bus port, the first resistor, the second resistor and the output circuit of the OBD port bus selection network circuit are connected in sequence; One end of the first diode is connected between the first resistor and the second resistor, and the other end of the first diode is used to be connected to the ground to limit the surge of the instantaneous high voltage signal; The fourth capacitor is connected in parallel with the third resistor, one end of the fourth capacitor is connected to one end of the third resistor and then connected to the ground, and the other end of the fourth capacitor is connected to the other end of the third resistor and then connected between the second resistor and the output circuit.

4. The vehicle bus level detection device according to claim 3, characterized in that: The first diode is a bidirectional TVS diode with a maximum breakdown voltage of 34V; And / or, the resistance value of the first resistor is selected as 90.9KΩ, with an accuracy of 1%, the resistance value of the second resistor R2 is selected as 9.1KΩ, with an accuracy of 1%, and the resistance value of the third resistor R3 is selected as 10KΩ, with an accuracy of 1%; And / or, the fourth capacitor is a ceramic chip capacitor.

5. The vehicle bus level detection device according to claim 1, characterized in that: The output circuit includes a precision operational amplifier and a fourth resistor which are connected in sequence. The precision operational amplifier is connected to the signal adjustment circuit. The fourth resistor is the output end of the output circuit and is used to be connected to the AD conversion port of the MCU.

6. The vehicle bus level detection device according to claim 5, characterized in that: The positive input terminal of the precision operational amplifier is connected to the signal adjustment circuit, the negative input terminal of the precision operational amplifier is connected to the output terminal of the precision operational amplifier and then connected to one end of the fourth resistor, and the other end of the fourth resistor is used to connect to the AD conversion port of the MCU.

7. The vehicle bus level detection device according to claim 1, characterized in that: It also includes an MCU, which includes an IO port line and an AD conversion port.

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