Serial port conversion circuit and equipment

Abstract

The utility model discloses a serial port conversion circuit and equipment, and relates to the technical field of communication port network connection, and the serial port conversion circuit comprises a signal input end and a signal output end; an RS232 conversion circuit, an RS485 conversion circuit and an RS422 conversion circuit, wherein the output end of the RS232 conversion circuit, the output end of the RS485 conversion circuit and the output end of the RS422 conversion circuit are all connected with the signal output end; the input end of the switching circuit is connected with the signal input end, the switching circuit is provided with three output ends, and the three output ends are connected with the input end of the RS232 conversion circuit, the input end of the RS485 conversion circuit and the input end of the RS422 conversion circuit respectively; the main control circuit is electrically connected with the controlled end of the switching circuit; the output end of the trigger circuit is electrically connected with the main control circuit, and the trigger circuit is used for outputting a corresponding trigger signal after being triggered; the utility model aims to solve the technical problem that the conversion function of the existing serial port equipment is relatively single.

Description

Technical Field

[0001] This utility model relates to the field of communication port networking technology, and in particular to a serial port conversion circuit and device. Background Technology

[0002] In the current field of electronic communications, the USB (Universal Serial Bus) interface has become the preferred interface for data transmission between various electronic devices due to its convenience, efficiency, and wide compatibility. Meanwhile, serial communication, as a traditional communication method, continues to play an important role in many fields, such as industrial automation, smart homes, and embedded system development.

[0003] To enable communication between USB interfaces and serial devices, various USB-to-serial converters and technologies are available on the market. These devices and technologies primarily convert USB interfaces to specific serial interfaces (such as RS232, RS422, RS485, and TTL). For example, a USB-to-RS232 device can convert data from a USB interface to RS232 data, thus enabling communication with devices that have an RS232 interface. Similarly, USB-to-RS422, USB-to-RS485, and USB-to-TTL devices also enable communication with their respective serial interface devices.

[0004] However, these existing serial port conversion devices and technologies have a significant drawback: their functionality is relatively limited. Specifically, each device can only correspond to one fixed serial interface, and cannot achieve one-to-many conversion. Utility Model Content

[0005] The main purpose of this utility model is to propose a serial port conversion circuit and device, which aims to solve the technical problem that the conversion function of existing serial port devices is relatively simple.

[0006] To achieve the above objectives, this utility model proposes a serial port conversion circuit, comprising:

[0007] Signal input terminal and signal output terminal;

[0008] RS232 conversion circuit, RS485 conversion circuit and RS422 conversion circuit, wherein the output terminals of the RS232 conversion circuit, the RS485 conversion circuit and the RS422 conversion circuit are all connected to the signal output terminal;

[0009] A switching circuit, wherein the input terminal of the switching circuit is connected to the signal input terminal, and the switching circuit has three output terminals, which are respectively connected to the input terminals of the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit;

[0010] The main control circuit is electrically connected to the controlled terminal of the switching circuit;

[0011] A trigger circuit, the output of which is electrically connected to the main control circuit, is used to output a corresponding trigger signal after being triggered;

[0012] The main control circuit is used to control the switching circuit to open the path between the signal input terminal and one of the input terminals of the RS232 conversion circuit, the RS485 conversion circuit, or the RS422 conversion circuit when the trigger signal is received.

[0013] In one embodiment, the switching circuit includes:

[0014] Three first switching transistors are respectively connected in series in the path between the signal input terminal and the input terminal of the RS232 conversion circuit, the path between the signal input terminal and the input terminal of the RS485 conversion circuit, and the path between the signal input terminal and the input terminal of the RS422 conversion circuit.

[0015] The controlled terminal of the first switching transistor is electrically connected to the main control circuit.

[0016] In one embodiment, the switching circuit further includes:

[0017] Three second switching transistors are provided, with the input terminals of the second switching transistors connected to the input terminals of the first switching transistors, and the output terminals of the second switching transistors connected to the output terminals of the first switching transistors.

[0018] The controlled terminal of the second switching transistor is electrically connected to the main control circuit.

[0019] In one embodiment, the switching circuit includes:

[0020] A multiplexer, wherein the input terminal of the multiplexer is connected to the signal input terminal, the multiplexer has a first output terminal, a second output terminal and a third output terminal, the first output terminal is connected to the input terminal of the RS232 conversion circuit, the second output terminal is connected to the input terminal of the RS485 conversion circuit, and the third output terminal is connected to the input terminal of the RS422 conversion circuit;

[0021] The controlled terminal of the multiplexer is electrically connected to the main control circuit.

[0022] In one embodiment, the serial port conversion circuit further includes:

[0023] Multiple filter circuits are respectively connected in series in the path between the output terminal of the RS232 conversion circuit and the signal output terminal, in the path between the output terminal of the RS485 conversion circuit and the signal output terminal, and in the path between the output terminal of the RS422 conversion circuit and the signal output terminal.

[0024] In one embodiment, the filtering circuit includes:

[0025] A first capacitor and a first transient suppression diode are provided. The first terminal of the first capacitor and the first terminal of the first transient suppression diode are respectively connected to one of the output terminals of the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit. The second terminal of the first capacitor and the second terminal of the first transient suppression diode are both grounded.

[0026] In one embodiment, the trigger circuit includes:

[0027] The display module has its signal output terminal electrically connected to the main control circuit. When the display module is triggered, it outputs a corresponding trigger signal to the main control circuit.

[0028] In one embodiment, the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit each have a first power input terminal, a second power input terminal, and a third power input terminal for connecting to the power supply voltage. The serial port conversion circuit further includes:

[0029] Three third switching transistors are respectively connected in series in the path between the first power input terminal and the supply voltage, the path between the second power input terminal and the supply voltage, and the path between the third power input terminal and the supply voltage.

[0030] The controlled terminal of the third switching transistor is electrically connected to the main control circuit.

[0031] In one embodiment, the serial port conversion circuit further includes:

[0032] A delay circuit, wherein the first end of the delay circuit is electrically connected to the main control circuit, and the second end of the delay circuit is connected to the controlled end of the switching circuit.

[0033] This utility model also proposes a serial port conversion circuit, including the serial port conversion circuit described in any of the above claims.

[0034] The technical solution of this utility model employs a series of switching circuits connected in the input terminals of the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit, as well as the signal input terminal. When the trigger circuit is activated, the main control circuit controls the switching circuit to open the path between the signal input terminal and one of the input terminals of the RS232, RS485, or RS422 conversion circuits. With this configuration, the serial port conversion circuit of this utility model can switch between the RS232, RS485, or RS422 conversion circuits to process the serial port signal at the signal input terminal based on the received trigger signal, outputting one of the RS232, RS485, or RS422 signals. Compared to existing serial port conversion devices, the serial port conversion device using this utility model's circuit can achieve multiple conversions from a single circuit and only requires one serial port interface for receiving serial signals, thus reducing the number of interfaces on the device and making it more streamlined. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a module according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the circuit structure of an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the circuit structure of another embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the circuit structure of another embodiment of the present invention.

[0041] Explanation of icon numbers:

[0042] 10. RS232 conversion circuit; 20. RS485 conversion circuit; 30. RS422 conversion circuit; 40. Switching circuit; 41. First switching transistor; 42. Second switching transistor; 50. Main control circuit; 60. Trigger circuit; 70. Filtering circuit; 80. Third switching transistor; 90. Delay circuit.

[0043] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0044] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0045] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0046] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0047] In the current field of electronic communications, the USB (Universal Serial Bus) interface has become the preferred interface for data transmission between various electronic devices due to its convenience, efficiency, and wide compatibility. Meanwhile, serial communication, as a traditional communication method, continues to play an important role in many fields, such as industrial automation, smart homes, and embedded system development.

[0048] To enable communication between USB interfaces and serial devices, various USB-to-serial converters and technologies are available on the market. These devices and technologies primarily convert USB interfaces to specific serial interfaces (such as RS232, RS422, RS485, and TTL). For example, a USB-to-RS232 device can convert data from a USB interface to RS232 data, thus enabling communication with devices that have an RS232 interface. Similarly, USB-to-RS422, USB-to-RS485, and USB-to-TTL devices also enable communication with their respective serial interface devices.

[0049] However, these existing serial port conversion devices and technologies have a significant drawback: their functionality is relatively limited. Specifically, each device can only correspond to one fixed serial interface, and cannot achieve one-to-many conversion.

[0050] Therefore, this utility model proposes a serial port conversion circuit and device, aiming to solve the technical problem that the conversion function of existing serial port devices is relatively simple.

[0051] refer to Figure 1 In one embodiment of this utility model, a serial port conversion circuit includes:

[0052] Signal input terminal and signal output terminal;

[0053] RS232 conversion circuit 10, RS485 conversion circuit 20 and RS422 conversion circuit 30, the output terminals of RS232 conversion circuit 10, RS485 conversion circuit 20 and RS422 conversion circuit 30 are all connected to the signal output terminal;

[0054] A switching circuit 40, the input terminal of which is connected to the signal input terminal, and the switching circuit 40 has three output terminals, which are respectively connected to the input terminals of the RS232 conversion circuit 10, the RS485 conversion circuit 20, and the RS422 conversion circuit 30.

[0055] The main control circuit 50 is electrically connected to the controlled terminal of the switching circuit 40.

[0056] A trigger circuit 60, the output terminal of which is electrically connected to the main control circuit 50, is used to output a corresponding trigger signal after being triggered;

[0057] The main control circuit 50 is used to control the switch circuit 40 to open the path between the signal input terminal and one of the input terminals of the RS232 conversion circuit 10, the RS485 conversion circuit 20, or the RS422 conversion circuit 30 when the trigger signal is received.

[0058] In this embodiment, the RS232 conversion circuit 10, the RS485 conversion circuit 20, and the RS422 conversion circuit 30 are used to convert the TTL level signal input from the signal input terminal into an RS232 serial port signal, an RS485 serial port signal, and an RS422 serial port signal, respectively.

[0059] In this embodiment, the main control circuit 50 can be implemented using a main controller, such as an MCU (Microcontroller Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a SOC (System On Chip).

[0060] In this embodiment, optionally, the switching circuit 40 can use multiple switching transistors, which are respectively connected in series in the path between the input terminal and signal input terminal of RS232 conversion circuit 10, the input terminal and signal input terminal of RS485 conversion circuit 20, and the input terminal and signal input terminal of RS422 conversion circuit 30. The main control circuit 50 controls one of the multiple switching transistors to be turned on according to the trigger signal output by the trigger circuit 60, so that one of RS232 conversion circuit 10, RS485 conversion circuit 20 and RS422 conversion circuit 30 processes the serial port signal input at the signal input terminal. Optionally, the switching circuit 40 can also be implemented using a multiplexer. The main control circuit 50 outputs corresponding control signals (e.g., 00, 10, and 11) based on the received trigger signal to control the multiplexer to open the path between the input terminal and the signal input terminal of one of the RS232 conversion circuit 10, RS485 conversion circuit 20, and RS422 conversion circuit 30, so that one of the RS232 conversion circuit 10, RS485 conversion circuit 20, and RS422 conversion circuit 30 processes the serial port signal input to the signal input terminal.

[0061] In this embodiment, the trigger circuit 60 can be implemented through multiple adjustment components, including buttons or knobs, or through a wireless communication module that establishes a wireless communication connection with an external terminal. The user triggers the adjustment components according to actual needs, or operates the external terminal to output a corresponding trigger signal. The main control circuit 50 controls the switching circuit 40 to connect the signal input terminal to one of the following input terminals: the RS232 conversion circuit 10, the RS485 conversion circuit 20, or the RS422 conversion circuit 30.

[0062] Specifically, the technical solution of this utility model employs a switch circuit 40 connected in series in the path between the input terminals of the RS232 conversion circuit 10, the RS485 conversion circuit 20, and the RS422 conversion circuit 30, and the signal input terminal. When the trigger circuit 60 is triggered, the main control circuit 50 controls the switch circuit 40 to open the path between the signal input terminal and one of the input terminals of the RS232 conversion circuit 10, RS485 conversion circuit 20, or RS422 conversion circuit 30. With this configuration, the serial port conversion circuit of this utility model can switch one of the RS232 conversion circuit 10, RS485 conversion circuit 20, or RS422 conversion circuit 30 to process the serial port signal at the signal input terminal according to the received trigger signal, so as to output an RS232 signal, an RS485 signal, or an RS422 signal. Compared to existing serial port conversion devices, the serial port conversion device using the serial port conversion circuit of this utility model can achieve one-to-many conversion, and only needs to be set up with one serial port interface for receiving serial port signals, thereby reducing the number of interfaces on the device and making the device more concise.

[0063] refer to Figure 2 In one embodiment of this utility model, the switching circuit 40 includes:

[0064] Three first switching transistors 41 are respectively connected in series in the path between the signal input terminal and the input terminal of the RS232 conversion circuit 10, the path between the signal input terminal and the input terminal of the RS485 conversion circuit 20, and the path between the signal input terminal and the input terminal of the RS422 conversion circuit 30.

[0065] The controlled terminal of the first switching transistor 41 is electrically connected to the main control circuit 50.

[0066] In this embodiment, the first switching transistor 41 can be implemented using a MOSFET, IGBT, thyristor, transistor, power transistor, etc., and / or using switching devices such as contactors, circuit breakers, or relays. The main control circuit 50, based on the trigger signal output by the trigger circuit 60, controls the path between one of the three first switching transistors 41's on signal input terminals and one of the input terminals of the RS232 conversion circuit 10, RS485 conversion circuit 20, or RS422 conversion circuit 30, so that one of the RS232 conversion circuit 10, RS485 conversion circuit 20, or RS422 conversion circuit 30 processes the serial port signal input to the signal input terminal.

[0067] In this embodiment, reference Figure 3 The switching circuit 40 further includes:

[0068] Three second switching transistors 42 are provided, with the input terminals of the second switching transistors 42 connected to the input terminals of the first switching transistors 41, and the output terminals of the second switching transistors 42 connected to the output terminals of the first switching transistors 41.

[0069] The controlled terminal of the second switching transistor 42 is electrically connected to the main control circuit 50.

[0070] In this embodiment, the second switch 42 can be implemented using a MOSFET, IGBT, thyristor, transistor, power transistor, etc., and / or using a switching device such as a contactor, circuit breaker, or relay. The second switch 42 serves as a backup switch in the event of a failure of the corresponding parallel first switch 41. That is, when the first switch 41 fails, the control circuit controls the second switch 42 connected in parallel with the failed first switch 41 to conduct. With this configuration, when a first switch 41 fails, the corresponding second switch 42 can immediately take over its operation, ensuring the normal operation of the circuit.

[0071] refer to Figure 4 In one embodiment of this utility model, the serial port conversion circuit further includes:

[0072] Multiple filter circuits 70 are respectively connected in series in the path between the output terminal of the RS232 conversion circuit 10 and the signal output terminal, the path between the output terminal of the RS485 conversion circuit 20 and the signal output terminal, and the path between the output terminal of the RS422 conversion circuit 30 and the signal output terminal.

[0073] In this embodiment, during signal transmission, the signal may be affected by factors such as environmental noise and electromagnetic interference, resulting in fluctuations or distortion. The filter circuit 70 can suppress these interference signals, ensuring the stability and accuracy of the output signal. By filtering out high-frequency noise and clutter, the filter circuit 70 can improve the signal-to-noise ratio, thereby improving communication quality.

[0074] In this embodiment, the filter circuit 70 can be implemented using an RC filter circuit 70, an LC filter circuit 70, an active bandpass filter, or a notch filter.

[0075] In this embodiment, the filter circuit 70 includes:

[0076] A first capacitor C1 and a first transient suppression diode D1 are connected, with the first end of the first capacitor C1 and the first end of the first transient suppression diode D1 respectively connected to one of the output terminals of the RS232 conversion circuit 10, the RS485 conversion circuit 20 and the RS422 conversion circuit 30. The second ends of the first capacitor C1 and the second ends of the first transient suppression diode D1 are both grounded.

[0077] The first capacitor C1 is primarily responsible for filtering high-frequency noise, while the first transient voltage suppressor diode D1 protects the circuit from voltage spikes and overvoltages. When an abnormal voltage occurs in the circuit, the first transient voltage suppressor diode D1 quickly conducts, diverting excess current to ground, thus protecting other components in the circuit from damage. This configuration, by filtering noise signals and protecting the circuit from abnormal voltages, together improves the circuit's anti-interference capability. Their coordinated operation ensures the stability and safety of the circuit.

[0078] In one embodiment of this utility model, the trigger circuit 60 includes:

[0079] The display module has its signal output terminal electrically connected to the main control circuit 50. The display module is used to output a corresponding trigger signal to the main control circuit 50 when it is triggered.

[0080] In this embodiment, the display module can directly display the current serial communication status, the selected communication protocol (such as RS232, RS485, RS422), or other relevant information. Through the display module, users can easily select and switch between serial communication protocols. For example, when it is necessary to change the communication protocol, the user only needs to view the information on the display module and then perform the corresponding operation as needed. This setup greatly simplifies the user's workflow and improves the user experience.

[0081] refer to Figure 5In one embodiment of this utility model, the RS232 conversion circuit 10, the RS485 conversion circuit 20, and the RS422 conversion circuit 30 respectively have a first power input terminal, a second power input terminal, and a third power input terminal for connecting the power supply voltage. The serial port conversion circuit further includes:

[0082] Three third switching transistors 80 are respectively connected in series in the path between the first power input terminal and the supply voltage VCC, the path between the second power input terminal and the supply voltage VCC, and the path between the third power input terminal and the supply voltage VCC.

[0083] The controlled terminal of the third switch 80 is electrically connected to the main control circuit 50.

[0084] In this embodiment, when the switching circuit 40 connects the input terminal and signal input terminal of any one of the RS232 conversion circuit 10, RS485 conversion circuit 20, and RS422 conversion circuit 30, the main control circuit 50 controls the third switching transistor 80 electrically connected to the power input terminal of that conversion circuit to turn on, and controls the third switching transistor 80 electrically connected to the power input terminals of the other two conversion circuits to turn off. This configuration ensures that when one conversion circuit is working, the other conversion circuits stop working, thereby avoiding unnecessary power consumption.

[0085] In this embodiment, the serial port conversion circuit further includes:

[0086] The delay circuit 90 has a first terminal electrically connected to the main control circuit 50 and a second terminal connected to the controlled terminal of the switching circuit 40.

[0087] In this embodiment, the delay circuit 90 can be implemented using at least one capacitor. Since the RS232 conversion circuit 10, RS485 conversion circuit 20 and RS422 conversion circuit 30 require a certain amount of time to initialize after being powered on and cannot immediately process the serial port signal, the delay circuit 90 is used to delay the conduction time of the switch circuit 40, thereby giving the conversion circuit sufficient preparation time and avoiding the situation where the serial port signal is lost or erroneous because the conversion circuit cannot immediately process the serial port signal when it is powered on.

[0088] This utility model also proposes a serial port conversion device, including the serial port conversion circuit as described above.

[0089] It is worth noting that since the serial port conversion device of this utility model is based on the above-mentioned serial port conversion circuit, the embodiments of the serial port conversion device of this utility model include all the technical solutions of all embodiments of the above-mentioned serial port conversion circuit, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0090] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A serial port conversion circuit, characterized in that, include: Signal input terminal and signal output terminal; RS232 conversion circuit, RS485 conversion circuit and RS422 conversion circuit, wherein the output terminals of the RS232 conversion circuit, the RS485 conversion circuit and the RS422 conversion circuit are all connected to the signal output terminal; A switching circuit, wherein the input terminal of the switching circuit is connected to the signal input terminal, and the switching circuit has three output terminals, which are respectively connected to the input terminals of the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit; The main control circuit is electrically connected to the controlled terminal of the switching circuit; A trigger circuit, the output of which is electrically connected to the main control circuit, is used to output a corresponding trigger signal after being triggered; The main control circuit is used to control the switching circuit to open the path between the signal input terminal and one of the input terminals of the RS232 conversion circuit, the RS485 conversion circuit, or the RS422 conversion circuit when the trigger signal is received.

2. The serial port conversion circuit as described in claim 1, characterized in that, The switching circuit includes: Three first switching transistors are respectively connected in series in the path between the signal input terminal and the input terminal of the RS232 conversion circuit, the path between the signal input terminal and the input terminal of the RS485 conversion circuit, and the path between the signal input terminal and the input terminal of the RS422 conversion circuit. The controlled terminal of the first switching transistor is electrically connected to the main control circuit.

3. The serial port conversion circuit as described in claim 2, characterized in that, The switching circuit also includes: Three second switching transistors are provided, with the input terminals of the second switching transistors connected to the input terminals of the first switching transistors, and the output terminals of the second switching transistors connected to the output terminals of the first switching transistors. The controlled terminal of the second switching transistor is electrically connected to the main control circuit.

4. The serial port conversion circuit as described in claim 1, characterized in that, The switching circuit includes: A multiplexer, wherein the input terminal of the multiplexer is connected to the signal input terminal, the multiplexer has a first output terminal, a second output terminal and a third output terminal, the first output terminal is connected to the input terminal of the RS232 conversion circuit, the second output terminal is connected to the input terminal of the RS485 conversion circuit, and the third output terminal is connected to the input terminal of the RS422 conversion circuit; The controlled terminal of the multiplexer is electrically connected to the main control circuit.

5. The serial port conversion circuit as described in claim 1, characterized in that, The serial port conversion circuit also includes: Multiple filter circuits are respectively connected in series in the path between the output terminal of the RS232 conversion circuit and the signal output terminal, in the path between the output terminal of the RS485 conversion circuit and the signal output terminal, and in the path between the output terminal of the RS422 conversion circuit and the signal output terminal.

6. The serial port conversion circuit as described in claim 5, characterized in that, The filtering circuit includes: A first capacitor and a first transient suppression diode are provided. The first terminal of the first capacitor and the first terminal of the first transient suppression diode are respectively connected to one of the output terminals of the RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit. The second terminal of the first capacitor and the second terminal of the first transient suppression diode are both grounded.

7. The serial port conversion circuit as described in claim 1, characterized in that, The trigger circuit includes: The display module has its signal output terminal electrically connected to the main control circuit. When the display module is triggered, it outputs a corresponding trigger signal to the main control circuit.

8. The serial port conversion circuit as described in claim 1, characterized in that, The RS232 conversion circuit, the RS485 conversion circuit, and the RS422 conversion circuit each have a first power input terminal, a second power input terminal, and a third power input terminal for connecting to the power supply voltage. The serial port conversion circuit further includes: Three third switching transistors are respectively connected in series in the path between the first power input terminal and the supply voltage, the path between the second power input terminal and the supply voltage, and the path between the third power input terminal and the supply voltage. The controlled terminal of the third switching transistor is electrically connected to the main control circuit.

9. The serial port conversion circuit as described in claim 8, characterized in that, The serial port conversion circuit also includes: A delay circuit, wherein the first end of the delay circuit is electrically connected to the main control circuit, and the second end of the delay circuit is connected to the controlled end of the switching circuit.

10. A serial port conversion device, characterized in that, Includes the serial port conversion circuit as described in any one of claims 1-9.

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