Isolation serial port circuit and data acquisition board

Abstract

The utility model provides an isolation serial port circuit and a data acquisition board, and belongs to the technical field of data acquisition equipment, the isolation serial port circuit comprises a power supply module, a voltage reduction and current stabilization module, a first optocoupler module, a second optocoupler module, a first data transmission port and a second data transmission port, the first data transmission port is connected with the input end of the power supply module, the output end of the power supply module is connected with the voltage reduction and current stabilization module, and the voltage reduction and current stabilization module is connected with the first optical coupler module, the second optical coupler module and the second data transmission port. The first optical coupler module and the second optical coupler module are respectively connected between the first data transmission port and the second data transmission port. By adopting the first optocoupler module and the second optocoupler module, isolation of serial port signals can be achieved, and therefore the purpose of high-low voltage isolation is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of data acquisition equipment, in particular to an isolation serial port circuit and a data acquisition board. Background Art

[0002] Data acquisition boards are key components for data acquisition and control in computer-based measurement and control systems. They are often integrated into applications such as industrial automation, laboratory test equipment, and environmental monitoring systems. They acquire data from various sensors and instruments and transmit this data to a computer for processing and analysis. Existing data acquisition boards typically consist of a main control microcontroller (MCU), peripheral communication circuits, and sensors. The main MCU is responsible for processing the sensor data and communicating with the peripheral circuits.

[0003] In related technologies, some new embedded AFE chips differ structurally from traditional MCU solutions. They integrate some traditional MCU functions and effectively reduce the development cost of data acquisition boards by eliminating the main MCU and peripheral communication circuits. However, since embedded AFE chips omit low-voltage circuitry, they do not require high- and low-voltage isolation. This means that serial port connections can only be processed with power off. When the battery is powered, data cannot be viewed on the host computer through the serial port connection. This not only affects system continuity but also increases operational complexity. Utility Model Content

[0004] In view of the above problems, in the first aspect, an embodiment of the present invention provides an isolated serial port circuit, which includes: a power supply module, a step-down and current stabilization module, a first optocoupler module, a second optocoupler module, a first data transmission port and a second data transmission port, wherein the first data transmission port is connected to the input end of the power supply module, the output end of the power supply module is connected to the step-down and current stabilization module, the step-down and current stabilization module is respectively connected to the first optocoupler module, the second optocoupler module and the second data transmission port, and the first optocoupler module and the second optocoupler module are respectively connected between the first data transmission port and the second data transmission port.

[0005] In one embodiment, the power module includes a power chip U2 , an input end of the power chip U2 is connected in parallel with a filter capacitor CE1 , and an output end of the power chip U2 is connected in parallel with capacitors C2 , C3 and CE2 .

[0006] In one embodiment, the step-down and current stabilization module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C5, a transistor M1 and a Zener diode ZD1, wherein the resistor R1, the resistor R2 and the resistor R3 are connected in series, the starting end of the series combination of the resistor R1, the resistor R2 and the resistor R3 is connected in parallel to the collector of the transistor M1, and the base of the transistor M1 is respectively connected to the end of the series combination of the resistor R1, the resistor R2 and the resistor R3, the first end of the resistor R4 and the The first end of the resistor R5 is connected in parallel, the second end of the resistor R4 is connected to the anode of the Zener diode ZD1, the second end of the resistor R5 is connected to the cathode of the Zener diode ZD1, the first ends of the resistor R6 and the resistor R7 are connected in parallel with the first end of the capacitor C5, the second end of the capacitor C5 is connected between the resistor R5 and the cathode of the Zener diode ZD1, the second end of the resistor R6 is connected to the emitter of the transistor M1, and the second end of the resistor R7 is connected to the anode of the Zener diode ZD1.

[0007] In one embodiment, the step-down and current stabilization module further includes a capacitor C1 and a capacitor C4, the capacitor C1 and the capacitor C4 are connected in parallel, a first end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the emitter of the transistor M1, and a second end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the positive electrode of the Zener diode ZD1.

[0008] In one embodiment, the first optocoupler module includes an optocoupler U1 and a transistor Q1, the AN pin of the optocoupler U1 is connected to the first power supply, the CAT pin of the optocoupler U1 is connected to the collector of the transistor Q1, the collector of the transistor Q1 is connected to the primary TXD signal terminal, the VCC pin of the optocoupler U1 is connected to the second power supply, the GND pin of the optocoupler U1 is grounded, and the VOUT pin of the optocoupler U1 is used to output the secondary TXD signal.

[0009] In one embodiment, the first optocoupler module further includes resistors R8, R9, R10, and R11. The AN pin of the optocoupler U1 is connected to the first power supply through the resistor R11, the resistor R8 is connected to the base and collector of the transistor Q1, the collector of the transistor Q1 is connected to the primary TXD signal terminal through the resistor R10, and the resistor R9 is arranged between the VOUT pin of the optocoupler U1 and the second power supply.

[0010] In one embodiment, the second optocoupler module includes an optocoupler U3 and a transistor Q2, the AN pin of the optocoupler U1 is connected to a third power supply, the CAT pin of the optocoupler U3 is connected to the collector of the transistor Q2, the collector of the transistor Q2 is connected to the primary side RXD signal terminal, the VCC pin of the optocoupler U3 is connected to a fourth power supply, the GND pin of the optocoupler U3 is grounded, and the VOUT pin of the optocoupler U3 is used to output the secondary side RXD signal.

[0011] In one embodiment, the second optocoupler module further includes a resistor R12, a resistor R13, a resistor R14 and a resistor R15, the AN pin of the optocoupler U3 is connected to the third power supply through the resistor R15, the resistor R14 is connected to the base and collector of the transistor Q2, the collector of the transistor Q2 is connected to the primary RXD signal terminal through the resistor R13, and the resistor R12 is arranged between the VOUT pin of the optocoupler U3 and the fourth power supply.

[0012] In a second aspect, an embodiment of the present invention further provides a data acquisition board, which includes an isolated serial port circuit as described in the above aspect.

[0013] The above one or more technical solutions in the embodiments of the present application have at least one or more of the following technical effects:

[0014] An isolated serial port electrical and data acquisition board provided in an embodiment of the present invention includes: a power supply module, a voltage-step-down and current-stabilizing module, a first optical coupler module, a second optical coupler module, a first data transmission port, and a second data transmission port. The power supply module is responsible for boosting the input power supply to the required voltage level to supply power to the subsequent circuit module. The voltage-step-down and current-stabilizing module is used to step down the high-voltage direct current output by the power supply module to a voltage level suitable for the operation of the subsequent circuit and provide a stable current output. The first optical coupler module is responsible for isolating the TXD signal on the primary side from the TXD signal on the secondary side, ensuring that the signals remain in phase during transmission. The optical coupler transmits information through optical signals, thereby achieving electrical isolation. The second optical coupler module is responsible for isolating the RXD signal on the primary side from the RXD signal on the secondary side, also ensuring that the signals are transmitted in phase. Similar to the first optical coupler module, the second optical coupler module transmits information through optical signals to achieve electrical isolation. The first data transmission port and the second data transmission port serve as data input and output bridges, realizing the transmission of serial port data. This isolated serial port circuit effectively solves the problems of security and stability in data transmission between high-voltage and low-voltage environments. By adopting the first optocoupler module and the second optocoupler module, the serial port signal can be isolated, thereby achieving the purpose of high and low voltage isolation. When the data acquisition board is battery-powered, the user can read and burn data in real time on the host computer by connecting the serial port, which greatly enhances the continuity of the system and reduces the complexity of operation.

[0015] The above description 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, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the circuit module of the isolated serial port circuit in the embodiment of the present utility model;

[0018] Figure 2 This is a schematic diagram of the circuit principles of the power module and the voltage-step-down and current-stabilizing module in an embodiment of the present utility model;

[0019] Figure 3 Schematic diagram of a circuit of a first optical coupling module in an embodiment of the present utility model;

[0020] Figure 4 Schematic diagram of the circuit of the second optical coupling module in an embodiment of the present invention.

[0021] Explanation of reference numerals: 100, power supply module; 200, step-down and current stabilization module; 300, first optocoupler module; 400, second optocoupler module; 500, first data transmission port; 600, second data transmission port. DETAILED DESCRIPTION

[0022] The overall idea of ​​the technical solution provided by this utility model is as follows:

[0023] See also Figure 1The isolated serial port circuit includes: a power module 100, a step-down and current stabilizing module 200, a first optical coupler module 300, a second optical coupler module 400, a first data transmission port 500 and a second data transmission port 600, wherein the first data transmission port 500 is connected to the input end of the power module 100, the output end of the power module 100 is connected to the step-down and current stabilizing module 200, the step-down and current stabilizing module 200 is respectively connected to the first optical coupler module 300, the second optical coupler module 400 and the second data transmission port 600, and the first optical coupler module 300 and the second optical coupler module 400 are respectively connected between the first data transmission port 500 and the second data transmission port 600.

[0024] Specifically, the power module 100 is responsible for boosting the input power to a required voltage level to supply power to subsequent circuit modules. The power module 100 may be a secondary battery with a reverse connection protection function.

[0025] The step-down and current stabilizing module 200 is used to step down the high-voltage direct current output by the power module 100 to a voltage level suitable for the operation of subsequent circuits and provide a stable current output. Furthermore, the core function of the step-down and current stabilizing module 200 is to step down the voltage and act as a load to prevent the actual power of the power module 100 load from being less than 10% of the rated output power, thereby causing voltage instability.

[0026] The first optical coupler module 300 is responsible for isolating the TXD signal on the primary side from the TXD signal on the secondary side, ensuring that the signals remain in phase during transmission. The optical coupler transmits information through optical signals, thereby achieving electrical isolation.

[0027] The second optical coupler module 400 is responsible for isolating the RXD signal on the primary side from the RXD signal on the secondary side, also ensuring that the signals are transmitted in phase. Similar to the first optical coupler module 300, the second optical coupler module 400 transmits information through optical signals to achieve electrical isolation.

[0028] The first data transmission port 500 and the second data transmission port 600 serve as data input and output bridges, realizing the transmission of serial port data.

[0029] In actual use, for example, when data is being sent from the first data transmission port 500 (transmitter), the TXD signal is transmitted to the second data transmission port 600 (receiver) via the first optical coupler module 300. Due to the isolation characteristics of the optical coupler, there is no direct electrical connection between the transmitting and receiving ends, effectively isolating the electrical environments of the two ports. Similarly, when data is being sent from the second data transmission port 600 (receiver), the RXD signal is transmitted to the first data transmission port 500 (transmitter) via the second optical coupler module 400, also achieving isolated signal transmission.

[0030] Through the above design, the isolated serial port circuit effectively solves the security and stability issues of data transmission between high-voltage and low-voltage environments. By using the first and second optocoupler modules 300 and 400, serial port signals can be isolated, thereby achieving high-voltage and low-voltage isolation. This allows the user to read and program data in real time on a host computer by connecting to the serial port when the data acquisition board is battery-powered, greatly enhancing system continuity and reducing operational complexity.

[0031] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] As you can understand, Data Acquisition Boards (DABs) are essential components in systems such as computer measurement and control systems (CMS) and battery management systems (BMS). They are widely used in various fields, including industrial automation, laboratory testing, environmental monitoring, energy management, etc.

[0033] See also Figure 2 , the power module 100 includes a power chip U2, the input end of the power chip U2 is connected in parallel with a filter capacitor CE1, and the output end of the power chip U2 is connected in parallel with a capacitor C2, a capacitor C3 and a capacitor CE2. Specifically, the power chip U2 is responsible for converting the input voltage into a stable output voltage. The filter capacitor CE1 connected in parallel to the input end of the power chip U2 is used to reduce the noise and ripple of the input power supply, providing a smoother voltage input to the power chip U2. When the input voltage fluctuates, CE1 can temporarily store or release charge, thereby reducing the instantaneous change of voltage, which helps to stabilize the working environment of the power chip and improve its performance and life. The capacitor C2, capacitor C3 and capacitor CE2 connected in parallel at the output end of the power chip U2 can absorb the instantaneous current fluctuations caused by load changes, provide a more stable voltage output to the load, further reduce the voltage ripple output by the power chip, and ensure the stability and purity of the output voltage.

[0034] See also Figure 2The step-down and current stabilizing module 200 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C5, a transistor M1, and a Zener diode ZD1. The resistor R1, the resistor R2, and the resistor R3 are connected in series, the starting end of the series combination of the resistor R1, the resistor R2, and the resistor R3 is connected in parallel to the collector of the transistor M1, and the base of the transistor M1 is connected to the end of the series combination of the resistor R1, the resistor R2, and the resistor R3, the first end of the resistor R4, and the collector of the transistor M1. The first end of R5 is connected in parallel, the second end of the resistor R4 is connected to the anode of the Zener diode ZD1, the second end of the resistor R5 is connected to the cathode of the Zener diode ZD1, the first ends of the resistor R6 and the resistor R7 are connected in parallel with the first end of the capacitor C5, the second end of the capacitor C5 is connected between the resistor R5 and the cathode of the Zener diode ZD1, the second end of the resistor R6 is connected to the emitter of the transistor M1, and the second end of the resistor R7 is connected to the anode of the Zener diode ZD1.

[0035] Specifically, resistors R1, R2, and R3 are connected in series to form a voltage divider network, which controls the voltage at the base of transistor M1. The on and off states of transistor M1 determine the output voltage. Resistors R4 and R5 are connected in parallel with the base of transistor M1 to limit the current between the base of transistor M1 and Zener diode ZD1. Zener diode ZD1 is used to maintain a stable reference voltage. Resistors R6 and R7 are connected in parallel with capacitor C5 to form a feedback network. Capacitor C5 stabilizes the feedback loop and reduces output voltage fluctuations. When the output voltage is less than a threshold, the voltage across resistor R7 is less than the reference voltage of Zener diode ZD1, turning off Zener diode ZD1 and turning on transistor M1, thereby increasing the output voltage. When the output voltage is greater than the threshold, the voltage across resistor R7 is greater than the reference voltage of Zener diode ZD1, turning on Zener diode ZD1 and turning off transistor M1, thereby reducing the output voltage. In this way, by dynamically adjusting the on-state of transistor M1, the circuit can maintain the output voltage around the threshold.

[0036] See also Figure 2 The step-down and current stabilization module 200 further includes a capacitor C1 and a capacitor C4, which are connected in parallel. A first end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the emitter of the transistor M1, and a second end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the positive electrode of the Zener diode ZD1. The function of the capacitor C1 and the capacitor C4 is to suppress low-frequency ripple in the output voltage to stabilize the DC output.

[0037] See also Figure 3, the first optocoupler module 300 includes an optocoupler U1 and a transistor Q1, the AN pin of the optocoupler U1 is connected to the first power supply, the CAT pin of the optocoupler U1 is connected to the collector of the transistor Q1, the collector of the transistor Q1 is connected to the primary TXD signal end, the VCC pin of the optocoupler U1 is connected to the second power supply, the GND pin of the optocoupler U1 is grounded, and the VOUT pin of the optocoupler U1 is used to output the secondary TXD signal. Specifically, when the primary TXD signal is at a high level, the transistor Q1 is turned on, the primary LED of the optocoupler U1 is illuminated, causing the secondary photosensitive element to be turned on. At this time, the VOUT pin of the optocoupler U1 outputs a low-level signal, realizing the in-phase transmission of the primary signal to the secondary signal. When the primary TXD signal is at a low level, the transistor Q1 is turned off, the primary LED of the optocoupler U1 is turned off, and the secondary photosensitive element is turned off. At this time, the VOUT pin of the optocoupler U1 outputs a high-level signal. Since the optocoupler uses optical signals to transmit electrical signals, electrical isolation is achieved between the primary and secondary sides. The first optocoupler module 300 achieves in-phase isolated transmission of the primary TXD signal and the secondary TXD signal through the combination of the optocoupler U1 and the transistor Q1.

[0038] See also Figure 3 The first optocoupler module 300 also includes resistors R8, R9, R10, and R11. The AN pin of the optocoupler U1 is connected to the first power supply via the resistor R11. The resistor R8 is connected to the base and collector of the transistor Q1. The collector of the transistor Q1 is connected to the primary TXD signal terminal via the resistor R10. The resistor R9 is located between the VOUT pin of the optocoupler U1 and the second power supply. Resistor R11 is used to limit the current flowing through the primary LED of the optocoupler U1, ensuring that it operates within an appropriate current range. Resistor R10 and resistor R8 form a feedback loop that helps to quickly respond to changes in the primary TXD signal and achieve rapid signal switching. Resistor R9 is on the secondary side of the optocoupler U1 and is connected to the second power supply. When the secondary photosensor is cut off, resistor R9 pulls the VOUT pin up to the level of the second power supply. As a pull-up resistor, resistor R9 ensures that the VOUT pin of the optocoupler U1 remains high when there is no signal input. In summary, resistor R11 limits the current in the primary LED, preventing overcurrent and protecting the LED and optocoupler U1. Resistors R8 and R10 ensure that transistor Q1 can quickly respond to changes in the primary signal, ensuring stable signal transmission. Resistor R9 acts as a pull-up resistor, ensuring that the VOUT pin remains high when no signal is input, contributing to circuit stability and reliability.

[0039] See also Figure 4, the second optocoupler module 400 includes an optocoupler U3 and a transistor Q2, the AN pin of the optocoupler U3 is connected to the third power supply, the CAT pin of the optocoupler U3 is connected to the collector of the transistor Q2, the collector of the transistor Q2 is connected to the primary RXD signal terminal, the VCC pin of the optocoupler U3 is connected to the fourth power supply, the GND pin of the optocoupler U3 is grounded, and the VOUT pin of the optocoupler U3 is used to output the secondary RXD signal. Similarly, when the primary RXD signal is high, the transistor Q2 is turned on, the primary LED of the optocoupler U3 is illuminated, causing the secondary photosensitive element to be turned on. At this time, the VOUT pin of the optocoupler U3 outputs a low-level signal, realizing the in-phase transmission of the primary signal to the secondary signal. When the primary RXD signal is low, the transistor Q2 is turned off, the primary LED of the optocoupler U3 is turned off, and the secondary photosensitive element is turned off. At this time, the VOUT pin of the optocoupler U3 outputs a high-level signal. Since the optocoupler uses light to transmit electrical signals, electrical isolation is achieved between the primary and secondary sides. The first optocoupler module 300 achieves in-phase isolated transmission of the primary RXD signal and the secondary RXD signal through the combination of the optocoupler U3 and the transistor Q2.

[0040] See also Figure 4 The second optocoupler module 400 also includes resistors R12, R13, R14, and R15. The AN pin of the optocoupler U3 is connected to the third power supply via resistor R15. Resistor R14 is connected to the base and collector of transistor Q2. The collector of transistor Q2 is connected to the primary RXD signal terminal via resistor R13. Resistor R12 is located between the VOUT pin of the optocoupler U3 and the fourth power supply. Resistor R15 is used to limit the current flowing through the primary LED of the optocoupler U3, ensuring that it operates within an appropriate current range. Resistor R13 and resistor R14 form a feedback loop that helps to quickly respond to changes in the primary TXD signal and achieve rapid signal switching. Resistor R12 is on the secondary side of the optocoupler U3 and is connected to the fourth power supply. When the secondary photosensor is turned off, resistor R12 pulls the VOUT pin up to the level of the fourth power supply, acting as a pull-up resistor. Resistor R12 ensures that the VOUT pin of the optocoupler U3 remains high when no signal is input. In summary, resistor R15 limits the current in the primary LED, preventing overcurrent and protecting the LED and optocoupler U3. Resistors R14 and R13 ensure that transistor Q2 can quickly respond to changes in the primary signal, ensuring stable signal transmission. Resistor R12 acts as a pull-up resistor, ensuring that the VOUT pin remains high when no signal is input, contributing to circuit stability and reliability.

[0041] An embodiment of the present invention further provides a data acquisition board, including an isolated serial port circuit as in the aforementioned embodiment. The various variations and specific embodiments in the aforementioned embodiment are also applicable to the data acquisition board of this embodiment. Through the aforementioned detailed description of a semiconductor sensor circuit, those skilled in the art can clearly understand the implementation method of the data acquisition board in this embodiment. For the sake of brevity of the specification, it will not be described in detail here.

[0042] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0043] Obviously, those skilled in the art may make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. An isolated serial port circuit, characterized in that: include: A power supply module, a step-down and current stabilizing module, a first optocoupler module, a second optocoupler module, a first data transmission port, and a second data transmission port, wherein the first data transmission port is connected to the input end of the power supply module, the output end of the power supply module is connected to the step-down and current stabilizing module, the step-down and current stabilizing module is respectively connected to the first optocoupler module, the second optocoupler module, and the second data transmission port, and the first optocoupler module and the second optocoupler module are respectively connected between the first data transmission port and the second data transmission port.

2. The isolated serial port circuit according to claim 1, characterized in that: The power module includes a power chip U2 . A filter capacitor CE1 is connected in parallel to the input end of the power chip U2 . A capacitor C2 , a capacitor C3 , and a capacitor CE2 are connected in parallel to the output end of the power chip U2 .

3. The isolated serial port circuit according to claim 2, characterized in that: The step-down and current stabilization module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C5, a transistor M1 and a Zener diode ZD1, wherein the resistor R1, the resistor R2 and the resistor R3 are connected in series, the starting end of the series combination of the resistor R1, the resistor R2 and the resistor R3 is connected in parallel to the collector of the transistor M1, and the base of the transistor M1 is respectively connected to the end of the series combination of the resistor R1, the resistor R2 and the resistor R3, the first end of the resistor R4 and the resistor R5 The first end of the resistor R6 and the resistor R7 are connected in parallel with the first end of the capacitor C5, the second end of the resistor R6 is connected to the emitter of the transistor M1, and the second end of the resistor R7 is connected to the anode of the Zener diode ZD1.

4. The isolated serial port circuit according to claim 3, characterized in that: The step-down and current stabilization module further includes a capacitor C1 and a capacitor C4, which are connected in parallel. A first end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the emitter of the transistor M1, and a second end of the parallel combination of the capacitor C1 and the capacitor C4 is connected to the positive electrode of the Zener diode ZD1.

5. The isolated serial port circuit according to claim 1, characterized in that: The first optocoupler module includes an optocoupler U1 and a transistor Q1, the AN pin of the optocoupler U1 is connected to the first power supply, the CAT pin of the optocoupler U1 is connected to the collector of the transistor Q1, the collector of the transistor Q1 is connected to the primary TXD signal terminal, the VCC pin of the optocoupler U1 is connected to the second power supply, the GND pin of the optocoupler U1 is grounded, and the VOUT pin of the optocoupler U1 is used to output the secondary TXD signal.

6. The isolated serial port circuit according to claim 5, characterized in that: The first optocoupler module also includes resistors R8, R9, R10 and R11. The AN pin of the optocoupler U1 is connected to the first power supply through the resistor R11, the resistor R8 is connected to the base and collector of the transistor Q1, and the collector of the transistor Q1 is connected to the primary TXD signal terminal through the resistor R10. The resistor R9 is arranged between the VOUT pin of the optocoupler U1 and the second power supply.

7. The isolated serial port circuit according to claim 1, characterized in that: The second optocoupler module includes an optocoupler U3 and a transistor Q2, the AN pin of the optocoupler U1 is connected to the third power supply, the CAT pin of the optocoupler U3 is connected to the collector of the transistor Q2, the collector of the transistor Q2 is connected to the primary side RXD signal end, the VCC pin of the optocoupler U3 is connected to the fourth power supply, the GND pin of the optocoupler U3 is grounded, and the VOUT pin of the optocoupler U3 is used to output the secondary side RXD signal.

8. The isolated serial port circuit according to claim 7, characterized in that: The second optocoupler module also includes resistors R12, R13, R14 and R15. The AN pin of the optocoupler U3 is connected to the third power supply through the resistor R15. The resistor R14 is connected to the base and collector of the transistor Q2. The collector of the transistor Q2 is connected to the primary RXD signal terminal through the resistor R13. The resistor R12 is arranged between the VOUT pin of the optocoupler U3 and the fourth power supply.

9. A data acquisition board, characterized in that: The invention comprises an isolated serial port circuit as described in any one of claims 1 to 8.

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