Serial port screen and 485 screen compatible circuit and charging system

Abstract

The application discloses a serial port screen and 485 screen compatible circuit and a charging system, wherein the circuit comprises: a main control module, one end of which is connected with an external power supply, and the other end of which is connected with a first node, the main control module being used for generating and outputting an instruction signal; a serial port screen interface module, one end of which is connected with the first node, and the other end of which is grounded, the serial port screen interface module being used for receiving the instruction signal and driving the serial port screen to display when the instruction signal indicates that the serial port screen displays; an RS-485 transceiving module, one end of which is connected with the external power supply, and the other end of which is connected with a level compatible module, the RS-485 transceiving module being used for receiving the instruction signal and driving the RS-485 screen to display when the instruction signal indicates that the RS-485 screen displays; and a level compatible module, one end of which is connected with the first node, and the other end of which is connected with the RS-485 transceiving module, the level compatible module being used for reducing the voltage of the first node, so that the instruction signal can be correctly recognized by the serial port screen interface module and the RS-485 transceiving module. The application can realize that the serial port screen and the 485 screen are driven by the same circuit system, and hardware switching is not needed.

Description

Technical Field

[0001] This application relates to the field of new energy vehicle charging technology, and in particular to a serial port screen and 485 screen compatible circuit and charging system. Background Technology

[0002] As a key interactive interface in the charging system, the display screen needs to support multiple types to adapt to different scenarios. For example, a UART serial port screen is used for local display, while an RS-485 screen is used for remote monitoring. In the design of the charging system, the communication interfaces of different display screens typically need to handle different voltage levels and signal protocols.

[0003] In traditional charging system solutions, the two screens require independent hardware circuits and main control serial ports, which leads to high system complexity, increased costs, and an inability to switch flexibly. Utility Model Content

[0004] The main purpose of this application is to provide a circuit and charging system compatible with serial port screens and 485 screens, aiming to solve the technical problem that existing serial port screens and 485 screens cannot be hardware compatible under a single signal path.

[0005] To achieve the above objectives, this application provides a serial port screen and RS-485 screen compatible circuit, comprising: a main control module, a serial port screen interface module, an RS-485 transceiver module, and a level compatibility module; the main control module is connected to an external power supply at one end and to a first node at the other end, and is used to generate and output command signals, which are used to instruct the serial port screen or RS-485 screen to display; the serial port screen interface module is connected to the first node at one end and grounded at the other end, and is used to receive the command signals and drive the serial port screen to display when the command signals instruct the serial port screen to display; the RS-485 transceiver module is connected to an external power supply at one end and to the level compatibility module at the other end, and is used to receive the command signals and drive the RS-485 screen to display when the command signals instruct the RS-485 screen to display; the level compatibility module is connected to the first node at one end and to the RS-485 transceiver module at the other end, and is used to reduce the voltage of the first node so that the command signals can be correctly recognized by the serial port screen interface module and the RS-485 transceiver module.

[0006] Optionally, the level-compatible module includes a voltage divider resistor; the voltage divider resistor is used to ensure that when the main control module outputs a low level, the voltage of the first node is less than 0.3V.

[0007] Optionally, the main control module includes: a control chip; the control chip is used to generate command signals, and the control chip integrates a third pull-up resistor internally.

[0008] Optionally, the serial port screen interface module includes a fourth resistor, one end of which is connected to the first node and the other end is grounded. The fourth resistor is used to form the equivalent load impedance of the serial port screen interface.

[0009] Optionally, the RS-485 transceiver module includes: a first resistor, one end of which is connected to an external power supply and the other end of which is connected to a level-compatible module. The first pull-up resistor is used to provide a bias voltage for the RS-485 bus in the RS-485 transceiver module.

[0010] Optionally, the serial port screen and RS-485 screen compatible circuit further includes: a terminal matching module, one end of which is connected to an external power supply, and the other end of which is connected between the level compatibility module and the RS-485 transceiver module. The terminal matching module includes a second resistor; the resistance value of the second resistor is matched with the characteristic impedance of the RS-485 bus to suppress the reflection of signals on the RS-485 bus at the end.

[0011] Optionally, the serial port screen and 485 screen compatible circuit further includes: a current limiting resistor, one end of which is connected to the serial port screen interface module and the other end of which is connected to the first node. The current limiting resistor is used to protect the chip pins of the main control module.

[0012] Optionally, the main control module is also used to receive data frames sent by the serial port screen interface module or the RS-485 transceiver module, and to perform integrity verification on the data frames.

[0013] Optionally, the main control module is further configured to parse the corresponding communication protocol according to the feature words in the data frame, so as to communicate with the serial port screen interface module or the RS-485 transceiver module.

[0014] Furthermore, to achieve the above objectives, this application also provides a charging system, comprising: the aforementioned serial port screen and RS-485 screen compatible circuit, a serial port screen, and an RS-485 screen; wherein, the serial port screen is connected to the serial port screen interface module and is used for display based on the drive signal of the serial port screen interface module; the RS-485 screen is connected to the RS-485 transceiver module and is used for display based on the drive signal of the RS-485 transceiver module.

[0015] This application proposes a serial port screen and RS-485 screen compatible circuit and charging system. By adding a level compatibility module between the main control module and the RS-485 transceiver module, when the main control module outputs a low-level command signal, the level compatibility module effectively reduces the voltage at the input terminal (first node) of the serial port screen interface module by increasing the equivalent impedance of the RS-485 branch. This solves the communication conflict problem in the prior art caused by the direct parallel connection of the RS-485 transceiver module and the serial port screen interface module, which results in excessively high low-level voltage and inability to be correctly identified. It achieves hardware compatibility and reliable communication between the serial port screen and the RS-485 screen on the same circuit board. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a first structure of a serial port screen and 485 screen compatible circuit provided in an embodiment of this application; Figure 2 This is a schematic diagram of a second structure of a serial port screen and 485 screen compatible circuit provided in an embodiment of this application; Figure 3 This is one of the flowcharts for the time-sharing strategy provided in the embodiments of this application; Figure 4 The second flowchart of the time-sharing strategy provided in the embodiments of this application; Figure 5 This is a schematic diagram of the charging system provided in an embodiment of this application.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0020] Furthermore, if the embodiments of this application 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 meaning of "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 in this application.

[0021] As a key interactive interface in the charging system, the display screen needs to support multiple types to adapt to different scenarios. For example, UART serial port screens are used for local display, while RS-485 screens are used for remote monitoring. In AC charging systems, screens with different interface types generally use different interfaces. UART serial port screens receive display commands through a simple asynchronous serial protocol, while RS-485, based on this, utilizes differential transmission characteristics to achieve anti-interference long-distance communication capabilities up to kilometers, making it suitable for driving screens distributed over long distances.

[0022] In traditional charging system solutions, a single board needs to integrate two independent serial communication circuits (such as level conversion chips and protection circuits) and occupy two UART interfaces of the main control chip, which consumes MCU resources. The hardware and system costs are high, and there is no flexible switching.

[0023] To address the aforementioned issues, this application provides a circuit and charging system compatible with both serial port and 485 screens. The solution described in this application will be detailed below.

[0024] It should be noted that existing technologies only involve voltage conversion of serial port screens, or only involve RS-485 communication, or involve interaction methods of serial port screens, but do not involve hardware connection and level conversion between serial port screens and RS-485 screens. That is, existing technologies cannot solve the level conflict problem caused by the difference between the input characteristics and bias circuits of UART serial port screens and RS-485 screens when their electrical interfaces are connected in parallel to the same master UART.

[0025] Based on this, embodiments of this application provide a circuit and charging system compatible with serial port screens and RS-485 screens, enabling a single UART interface to drive two display devices with different interface specifications (UART serial port screen and RS-485 screen) through time-division multiplexing.

[0026] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the first structure of the serial port screen and 485 screen compatible circuit provided in the embodiments of this application. The serial port screen and 485 screen compatible circuit may include: a main control module 110, a serial port screen interface module 120, an RS-485 transceiver module 130, and a level compatibility module 140.

[0027] In this embodiment, one end of the main control module 110 is connected to an external power supply, and the other end is connected to the first node N1. The main control module 110 generates and outputs command signals to select between communicating with a serial port screen or an RS-485 screen. One end of the serial port screen interface module 120 is connected to the first node N1, and the other end is grounded. It receives command signals and drives the serial port screen to display when the command signal instructs it to do so. One end of the RS-485 transceiver module 130 is connected to an external power supply, and the other end is connected to the main control module 110 via a level compatibility module 140. It receives command signals and drives the RS-485 screen to display when the command signal instructs it to do so. One end of the level compatibility module 140 is connected to the first node N1, and the other end is connected to the RS-485 transceiver module 130. It reduces the voltage of the first node N1 so that the command signals can be correctly recognized by the serial port screen interface module 120 and the RS-485 transceiver module 130. In this embodiment, the external power supply is set to 3.3V.

[0028] It should be noted that since both the RS-485 transceiver module 130 and the serial port screen interface module 120 contain pull-up resistors, when the RS-485 transceiver module 130 and the serial port screen interface module 120 are directly connected, due to the effect of the pull-up resistors, when the main control module 110 outputs a low level, the serial port screen interface module 120 will receive a voltage greater than 0.3V, which will prevent the serial port screen from recognizing it as a low level, resulting in communication failure.

[0029] Understandably, when the pin of the control chip in the main control module 110 outputs a low level (logic 0), its internal MOSFET pulls the signal line to ground through an impedance. However, the pull-up resistors inside the RS-485 transceiver module 130 and the main control module 110 form a low-impedance pull-up path, generating a continuous pull-up current. When the voltage drop generated by this pull-up current on the connection line between the serial port interface module 120 and the main control module 110 exceeds the maximum low-level input voltage threshold (0.3V) of the serial port interface, it will cause a logic level recognition error.

[0030] Based on this, this exemplary embodiment adds a level compatibility module 140 between the main control module 110 and the RS-485 transceiver module 130. The level compatibility module 140 includes at least one resistor, so that when the main control module 110 outputs a low level, the receiving voltage of the serial port screen interface module 120 is less than 0.3V, thereby ensuring the normal operation of the serial port screen, that is, ensuring that the serial port screen and the 485 screen can be driven by the same circuit system and communicate normally.

[0031] It should be understood that Figure 1 As an example only, this embodiment does not impose a specific limit on the number of resistors inside the level compatibility module 140. This exemplary embodiment ensures that a low-level voltage value conforming to the UART serial port screen input specification is generated at the target node (the input terminal of the serial port screen interface module 120) by introducing the level compatibility module 140, thereby ensuring continuous communication.

[0032] This application proposes a serial port screen and RS-485 screen compatible circuit and charging system. By adding a level compatibility module 140 between the main control module 110 and the RS-485 transceiver module 130, when the main control module 110 outputs a low-level command signal, the level compatibility module 140 effectively reduces the voltage at the input terminal (first node N1) of the serial port screen interface module 120 by increasing the equivalent impedance of the RS-485 branch. This solves the communication conflict problem in the prior art caused by the direct parallel connection of the RS-485 transceiver module 130 and the serial port screen interface module 120, resulting in excessively high low-level voltage and inability to be correctly identified. This achieves hardware compatibility and reliable communication between the serial port screen and the RS-485 screen on the same circuit board. The working principle and results of the serial port screen and 485 screen compatible circuit provided in this application will be further explained below with reference to the accompanying drawings.

[0033] In an exemplary embodiment, please refer to Figure 2 , Figure 2 This is a schematic diagram of a second structure of a serial port screen and RS-485 screen compatible circuit provided in an embodiment of this application. The serial port screen and RS-485 screen compatible circuit includes: a main control module 110, a serial port screen interface module 120, an RS-485 transceiver module 130, a level compatibility module 140, a terminal matching module 150, and a current limiting resistor R22.

[0034] The terminal matching module 150 is connected in parallel with the RS-485 transceiver module 130. One end of the terminal matching module 150 is connected to an external power supply, and the other end is connected between the level compatibility module 140 and the RS-485 transceiver module 130. The terminal matching module 150 includes a second resistor R2. The resistance value of the second resistor R2 is matched with the characteristic impedance of the RS-485 bus in the RS-485 transceiver module 130 to suppress the reflection of the signal on the RS-485 bus at the end. One end of the current limiting resistor R22 is connected to the serial port screen interface module 120, and the other end is connected to the first node N1. The current limiting resistor R22 is used to protect the chip pins of the main control module 110.

[0035] For example, the level compatibility module 140 includes a voltage divider resistor R10, which is used to ensure that the voltage of the first node N1 is less than 0.3V when the main control module 110 outputs a low level; the main control module 110 includes a control chip; the control chip is used to generate command signals, and the control chip internally integrates a third pull-up resistor R3; the serial port screen interface module 120 includes a fourth resistor R4, which is used to form the equivalent load impedance of the serial port screen interface; the RS-485 transceiver module 130 includes a first pull-up resistor R1, one end of which is connected to an external power supply, and the other end is connected to the level compatibility module 140, which is used to provide a bias voltage for the RS-485 bus in the RS-485 transceiver module.

[0036] It should be noted that the current-limiting resistor R22 can limit the peak current flowing into the control chip pins of the main control module 110 under abnormal conditions (such as hot-plugging or port short circuit), providing electrical protection. The resistance of the second resistor R2 is equal to the characteristic impedance of the RS-485 bus (120Ω for inflow), which can be used to achieve impedance matching, absorb signal energy to eliminate signal reflection caused by impedance discontinuity at the end of the bus, and ensure the quality of long-distance communication.

[0037] For ease of understanding, the following sections will describe the impact of removing and adding the level compatibility module 140 on the display of the serial port screen and the 485 screen, respectively.

[0038] It should be noted that when the level compatibility module 140 is removed in this embodiment, the parallel resistance value of the first pull-up resistor R1, the second resistor R2, and the third pull-up resistor R3 is: R 并 = (R1 / / R2 / / R3), when the main control module 110 outputs a low level, the input voltage of the serial port screen interface module 120 can be calculated according to the following formula (1): (1) Wherein, the first pull-up resistor R1 is the internal pull-up resistor of the 485 screen, with a resistance value in the ohm range; the fourth resistor R4 is the grounding resistor of the serial port screen; and the current-limiting resistor R22 is the external matching resistor, with a resistance value in the ohm range. In this embodiment, the first pull-up resistor R1 is set to 40Ω, the second resistor R2 to 120Ω, the third pull-up resistor R3 to 10kΩ, the fourth resistor R4 to 10Ω, and the current-limiting resistor R22 to 10Ω.

[0039] When the serial port screen interface module 120 outputs "0", it requires... <0.3V, while =1.33V>0.3V, the serial port screen cannot recognize it as a low level, thus communication fails.

[0040] Understandably, this is to reduce the input voltage of the serial port screen interface module 120. This can increase R 并， The resistance values ​​of the fourth resistor R4 and the current-limiting resistor R22 can also be reduced, but the fourth resistor R4 and the current-limiting resistor R22 are already very small, both in the ohm range.

[0041] Based on this, in this embodiment, a voltage divider resistor R10 is added between the second resistor R2 and the third pull-up resistor R3 to increase R... 并 The resistance value is such that when the main control module 110 outputs a low level, the receiving voltage of the serial port screen interface module 120 is less than 0.3V.

[0042] When the level compatibility module 140 is added to this embodiment, the parallel resistance value of the first pull-up resistor R1, the second resistor R2, the voltage divider resistor R10, and the third pull-up resistor R3 is: =[(R1 / / R2)+R10] / / R3, when the main control module 110 outputs a low level, the input voltage of the serial port screen interface module 120 is... It can be calculated according to the following formula (2): (2) In order to make For voltages less than 0.3V, the voltage divider resistor R10 needs to be greater than 0.68kΩ. In this embodiment, the resistance of the voltage divider resistor R10 is set to 1kΩ. Of course, in other embodiments, the resistance of the voltage divider resistor R10 can also be set to other values. This resistance value is required to ensure that when the main control module 110 outputs a low level, the receiving voltage of the serial port screen interface module 120 is less than 0.3V.

[0043] It should be noted that the upper limit of the voltage divider resistor R10's value is determined by the RS-485 communication rate requirements. In this embodiment, 1kΩ is selected as the nominal value of the voltage divider resistor R10, which can meet the low-level noise margin and maintain the communication rate. In addition, this resistance value is a commonly used specification, which can reduce procurement costs.

[0044] Therefore, the hardware of this application embodiment satisfies the requirement that the MCU's UART_TX is simultaneously connected to the DI (data input) of the RS-485 transceiver in the RS-485 transceiver module 130 and the RX (shared TX line) of the UART serial port screen in the serial port screen interface module 120; the MCU's UART_RX is simultaneously connected to the RO (data output) of the RS-485 transceiver in the RS-485 transceiver module 130 and the TX (shared RX line) of the UART serial port screen in the serial port screen interface module 120, so that the serial port screen and the 485 screen are driven by the same circuit system without the need for hardware switching.

[0045] This embodiment achieves software-level compatibility between a serial port screen (using a UART serial port screen as an example) and an RS-485 screen through a time-sharing switching strategy.

[0046] Figure 3 and Figure 4 The following is a flowchart illustrating the time-sharing strategy provided in an embodiment of this application. Figure 3 and Figure 4 The time-sharing strategy provided in the embodiments of this application will be further explained.

[0047] In the specific implementation process, UART initialization is performed first, that is, the communication baud rate is set to a fixed value (e.g., 115200); secondly, the communication mode corresponding to the screen to be displayed is dynamically switched according to the screen currently being displayed.

[0048] In this embodiment, the main control module 110 needs to be configured with two independent instruction sets or data frames, namely the communication modes and instruction functions of the UART serial port screen and the RS-485 screen. The main control module 110 can call the corresponding instruction function to process according to the currently active communication mode, thereby realizing flexible switching of instruction sets.

[0049] Specifically, please first refer to Figure 3 , Figure 3 This is one of the flowcharts for the time-sharing strategy provided in the embodiments of this application. In this embodiment, after UART initialization, the screen is set to be a serial port screen by default, and a detection signal is sent to detect the current screen type. If the screen is detected as a UART serial port screen, the communication protocol of the UART serial port screen is called; if the screen is detected as an RS-485 screen, the communication protocol of the RS-485 screen is called.

[0050] UART is an asynchronous serial communication protocol that can specify the data frame format and transmission rate. It should be noted that the UART initialization in this embodiment can establish a unified rate basis for communication between the two screens.

[0051] Further, please refer to Figure 4 , Figure 3 The second flowchart of the time-sharing strategy provided in this application embodiment shows that the control chip in the main control module 110 first performs integrity verification on the data sent by the UART serial port screen or RS-485 screen. If the data is complete, it determines whether the current communication mode is UART mode or RS-485 mode. If it is UART mode, i.e., communication with the UART serial port screen is required, it is necessary to ensure that the RS-485 transceiver is in a disabled high-impedance state (receive mode) to prevent it from affecting the communication bus. Then, the communication protocol (UART screen communication protocol) corresponding to the communication mode is parsed and data frames conforming to the serial port screen's private protocol are sent. If it is RS-485 mode, i.e., communication with the RS-485 screen is required, the RS-485 transceiver needs to be enabled through the GPIO pin to enter the transmit mode. Then, the communication protocol (Modbus communication protocol) is parsed and data frames conforming to the Modbus standard protocol are sent. After the data transmission is completed, the RS-485 transceiver is immediately switched back to receive mode to receive the RS-485 screen's response. It should be noted that if the data is incomplete, it continues to wait to receive data.

[0052] In addition, to ensure that the hardware in the circuit tends to stabilize after mode switching and to prevent mutual interference between data frames, this embodiment can also insert a delay of a preset time length after switching the RS-485 transceiver enable state to ensure system stability.

[0053] It should be noted that if both screens can actively send or receive data, the control chip needs to know which communication mode is currently in order to parse the received data using the corresponding communication protocol. For example, it can distinguish between them using data frames containing addresses or feature words, or it can determine the mode based on the previous communication mode. In this embodiment, when communication with a particular screen is required, it switches to the corresponding "communication mode" and adopts the protocol and timing of that mode.

[0054] Another embodiment of this application also provides a charging system; please refer to [link / reference needed]. Figure 5 , Figure 5 This is a schematic diagram of the charging system provided in the embodiment of this application. The charging system includes at least two charging modules 410, a controller 430, a power distribution device 440, at least one charging interface 420, and a display module 450.

[0055] The display module 450 is connected to the controller 430. The display module 450 includes a serial port screen and 485 screen compatible circuit, a serial port screen and an RS-485 screen. The serial port screen is connected to the serial port screen interface module and is used for display based on the drive signals of the serial port screen interface module. The RS-485 screen is connected to the RS-485 transceiver module and is used for display based on the drive signals of the RS-485 transceiver module. The power distribution device 440 is connected to the controller 430, each charging module 410 and each charging interface 420 respectively; The charging module 410 is used to convert AC power from the power grid into DC power and supply it to the charging interface; The controller 430 is used to obtain the power demand of each charging interface 420 and generate scheduling instructions according to the connection relationship of the controllable switches in the power distribution device 440 and the power demand; the controller 430 is also used to perform heat dissipation control on the charging system based on the above control method. The power distribution device 440 is used to control the opening or closing of the controllable switch according to the scheduling command, so as to distribute the output power of each charging module to each charging interface 420.

[0056] In one optional implementation, the charging system provided in this application is an integrated DC charging pile, with the charging interface 420 used to connect the charging gun, and the charging gun being hung on the host of the charging system via the gun holder on the main body of the charging system.

[0057] In one optional implementation, the charging system provided in this application embodiment is a split-type DC charging pile. The charging system also includes multiple charging terminals. The charging interface 420 is used to connect the charging terminals. The charging terminals are set separately from the main body of the charging system. The charging terminals are equipped with a single charging gun or dual charging guns for outputting power to electric vehicles.

[0058] It is understandable that the display module 450 is connected to the controller 430. The controller 430 can send control signals to the display module 450 according to the charging status of each charging terminal to select a serial port screen or an RS-485 screen for display.

[0059] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A serial port screen and 485 screen compatible circuit, characterized in that, include: Main control module, serial port screen interface module, RS-485 transceiver module and level compatibility module; The main control module is connected to an external power supply at one end and to the first node at the other end. The main control module is used to generate and output command signals, which are used to instruct the serial port screen or RS-485 screen to display. The serial port screen interface module has one end connected to the first node and the other end grounded. It is used to receive the instruction signal and drive the serial port screen to display when the instruction signal instructs the serial port screen to display. The RS-485 transceiver module is connected to an external power supply at one end and to the level compatibility module at the other end. It is used to receive the command signal and drive the RS-485 screen to display when the command signal instructs the RS-485 screen to display. A level-compatible module, with one end connected to the first node and the other end connected to the RS-485 transceiver module, is used to reduce the voltage of the first node so that the command signal can be correctly recognized by the serial port screen interface module and the RS-485 transceiver module.

2. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The level-compatible module includes: voltage divider resistors; The voltage divider resistor is used to ensure that the voltage of the first node is less than 0.3V when the main control module outputs a low level.

3. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The main control module includes: a control chip; The control chip is used to generate command signals, and the control chip integrates a third pull-up resistor.

4. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The serial port screen interface module includes: The fourth resistor has one end connected to the first node and the other end grounded. The fourth resistor is used to form the equivalent load impedance of the serial port screen interface.

5. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The RS-485 transceiver module includes: The first pull-up resistor has one end connected to an external power supply and the other end connected to a level compatibility module. The first pull-up resistor is used to provide a bias voltage for the RS-485 bus in the RS-485 transceiver module.

6. The serial port screen and 485 screen compatible circuit according to claim 5, characterized in that, The serial port screen and 485 screen compatible circuit also includes: The terminal matching module has one end connected to an external power supply and the other end connected between the level compatibility module and the RS-485 transceiver module. The terminal matching module includes a second resistor. The resistance value of the second resistor is matched with the characteristic impedance of the RS-485 bus to suppress signal reflection at the end of the RS-485 bus.

7. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The serial port screen and 485 screen compatible circuit also includes: A current-limiting resistor is connected at one end to the serial port screen interface module and at the other end to the first node. The current-limiting resistor is used to protect the chip pins of the main control module.

8. The serial port screen and 485 screen compatible circuit according to claim 1, characterized in that, The main control module is also used to receive data frames sent by the serial port screen interface module or the RS-485 transceiver module, and to perform integrity verification on the data frames.

9. The serial port screen and 485 screen compatible circuit according to claim 8, characterized in that, The main control module is also used to parse the corresponding communication protocol according to the feature words in the data frame, so as to communicate with the serial port screen interface module or the RS-485 transceiver module.

10. A charging system, characterized in that, include: The display module includes: a serial port screen and RS-485 screen compatible circuit, a serial port screen, and an RS-485 screen as described in any one of claims 1-9; The serial port screen is connected to the serial port screen interface module and is used to display based on the drive signals of the serial port screen interface module; the RS-485 screen is connected to the RS-485 transceiver module and is used to display based on the drive signals of the RS-485 transceiver module.

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