Communication terminal resistance matching circuit and control method for air conditioning system

Abstract

The present invention provides a resistance matching circuit and control method for a communication terminal in an air conditioning system, comprising: an air conditioning controller, an analog electronic switch, a digital potentiometer, a first resistor, and a short-circuit current-limiting protection circuit. The analog electronic switch includes a first switch and a second switch, wherein the normally closed end of the first switch and the normally closed end of the second switch are respectively connected to the first output end and the second output end of a communication interface, the common end of the first switch and the common end of the second switch are respectively connected to the ends of an adjustable resistor of the digital potentiometer, the normally open end of the first switch is grounded via the first resistor, and the normally open end of the second switch is connected to a sampling circuit power supply; the sampling port of the air conditioning controller is connected between the first resistor and the digital potentiometer. The present invention has a simple and efficient circuit, requires few components, is low cost, occupies a small space, and has a reasonable and efficient automatic matching process.

Description

Technical Field

[0001] The present invention relates to the field of air-conditioning communication, in particular to a communication terminal resistance matching circuit of an air-conditioning system, and to a control method for the communication terminal resistance matching circuit of the air-conditioning system. Background Art

[0002] During the communication debugging process of precision air conditioners, improper terminal resistance matching can cause data frame loss or errors. Connecting appropriate terminal resistance is an effective way to solve the problem of obstacles encountered during the transmission of electronic information.

[0003] Precision air conditioners generally undergo on-site debugging to determine whether the terminal resistance value matches the circuit. If it does not match, on-site manual debugging and matching are required. However, the implementation plan for terminal resistance matching is relatively complex and the debugging efficiency is low.

[0004] Currently, communication terminal resistance circuits in the industry are mainly divided into two categories: the first category is achieved through series connection through jumpers and 120Ω resistors. The output of the communication chip is connected in parallel with the jumpers and 120Ω resistors. Once this method is used to connect multiple devices, there is a risk of communication failure due to complex on-site connection conditions. It may be necessary to determine the terminal resistance value for circuit matching after on-site debugging. The corresponding terminal resistance matching implementation solution is relatively complex and the debugging efficiency is low.

[0005] The second type is a resistor automatic matching circuit including a resistor network unit, a resistor control unit, and a resistance measurement unit terminal. The resistor network unit is composed of M resistors connected in series; the resistor control unit is composed of M relays, and the M relays are respectively arranged in parallel with the M resistors; the corresponding resistors are connected / short-circuited by controlling the relays to open / close; the resistance measurement circuit includes a test power interface and an ADC conversion circuit. The test power interface and the resistor network unit form a series loop as a whole. The ADC conversion circuit is connected in parallel with one of the M resistors and is used to measure the voltage divided on the resistor when the test power is connected to calculate whether the terminal resistor connection resistance value is correct. The disadvantages of this method are: the circuits of the resistor network unit and the resistor control unit are complex, there are many devices, it takes up a lot of space and the cost is high. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an air-conditioning system communication terminal resistance matching circuit with a simple circuit structure and the ability to improve debugging efficiency. On this basis, a control method for the air-conditioning system communication terminal resistance matching circuit is further provided to solve the technical problems of many components, large space occupation and high cost, and to achieve efficient automatic matching of the air-conditioning system communication terminal resistance.

[0007] In this regard, the present invention provides a communication terminal resistance matching circuit for an air-conditioning system, comprising: an air-conditioning controller, an analog electronic switch, a digital potentiometer, a first resistor, and an anti-short-circuit current limiting protection circuit, wherein the analog electronic switch comprises a first switch and a second switch, wherein the normally closed end of the first switch and the normally closed end of the second switch are respectively connected to the first output end and the second output end of the communication interface, the common end of the first switch and the common end of the second switch are respectively connected to the two ends of the adjustable resistor of the digital potentiometer, the normally open end of the first switch is grounded through the first resistor, and the normally open end of the second switch is connected to a sampling circuit power supply; the sampling port of the air-conditioning controller is connected between the first resistor and the digital potentiometer, and after the normally open end of the first switch and the normally open end of the second switch are closed, the sampling port of the air-conditioning controller measures the voltage value of the connection midpoint between the first resistor and the digital potentiometer, and the air-conditioning controller calculates and confirms the adjustable resistance value of the digital potentiometer; the first switch and the second switch are respectively connected to the anti-short-circuit current limiting protection circuit.

[0008] A further improvement of the present invention is that the control pin of the first switch and the control pin of the second switch are electrically connected to the control pin of the air-conditioning controller, and the air-conditioning controller sends a control signal to control the synchronous on and off of the first switch and the second switch.

[0009] A further improvement of the present invention is that, in a default state, the common end and the normally closed end of the first switch are in a closed state, and the common end and the normally closed end of the second switch are in a closed state; if it is necessary to detect the resistance value of the terminal resistor, the air-conditioning controller sends a control signal to the control pin of the first switch and the control pin of the second switch to control the common end and the normally open end of the first switch to be converted to a closed state, and controls the common end and the normally open end of the second switch to be converted to a closed state. After the state conversion, the voltage value of the connection midpoint between the first resistor and the digital potentiometer is detected through the sampling port of the air-conditioning controller.

[0010] A further improvement of the present invention is that the common end of the first switch and the common end of the second switch are respectively connected to the L end and the W end of the adjustable resistor of the digital potentiometer.

[0011] A further improvement of the present invention is that the digital potentiometer is connected to the 2 The C serial bus is connected to the communication pin of the air-conditioning controller to adjust the resistance value of the adjustable resistor of the digital potentiometer.

[0012] A further improvement of the present invention is that the anti-short circuit current limiting protection circuit includes a second resistor, a third resistor, a first suppression diode, a second suppression diode and a third suppression diode, one end of the second resistor is connected to the common end of the second switch, the other end of the second resistor is respectively connected to one end of the first suppression diode, one end of the second suppression diode and the second output end of the communication interface, the other end of the first suppression diode is grounded, one end of the third resistor is connected to the common end of the first switch, the other end of the third resistor is respectively connected to the other end of the second suppression diode, one end of the third suppression diode and the first output end of the communication interface, and the other end of the third suppression diode is grounded.

[0013] The present invention also provides a control method for a communication terminal resistance matching circuit of an air conditioning system, which is used to control the communication terminal resistance matching circuit of the air conditioning system as described above, and includes the following steps:

[0014] Step S1, setting the operating mode of the air conditioning system communication terminal resistance matching circuit through the touch screen. If it is set to manual matching mode, jump to step S2; if it is set to automatic matching mode, jump to step S3;

[0015] Step S2, setting the resistance value of the digital potentiometer by detecting the input signal of the touch screen;

[0016] Step S3, automatically detecting the terminal resistance value after networking, and adjusting the digital potentiometer according to the preset terminal resistance setting value to achieve setting and adjustment of the terminal resistance value.

[0017] A further improvement of the present invention is that in step S2, after detecting and confirming that the corresponding terminal resistance value is set, the terminal resistance setting value on the touch screen is sent to the air conditioning controller, and the communication pin of the air conditioning controller is connected via I 2 The C serial bus sends the terminal resistance setting value to the serial bus pin of the digital potentiometer, and adjusts the adjustable resistor L end and W end of the digital potentiometer to the terminal resistance setting value.

[0018] A further improvement of the present invention is that step S3 includes the following sub-steps:

[0019] Step S301, setting and confirming the corresponding automatically matched terminal resistance setting value through the touch screen;

[0020] Step S302: Before communication begins, the adjustable resistors L and W of the digital potentiometer are first adjusted to the set terminal resistance values. Then, the equivalent resistance value of the terminal resistance in the actual circuit after networking is detected and calculated. The air conditioner controller then compares the terminal resistance set value with the equivalent resistance value in the actual circuit and adjusts the adjustable resistance of the digital potentiometer until the error between the terminal resistance set value and the equivalent resistance value is within an allowable range. This determines that the match is successful, and communication preparation begins. The first and second switches of the analog electronic switch are switched from normally open to normally closed to initiate data communication.

[0021] Step S303, during the communication circuit transceiver conversion process of the communication interface, repeat step S302 to automatically match the terminal resistance, and after the matching is completed, return to the communication mode by switching the analog electronic switch.

[0022] A further improvement of the present invention is that, in step S302, the process of detecting and calculating the equivalent resistance value of the terminal resistor in the actual circuit after networking is as follows: the first switch and the second switch of the analog electronic switch are converted from normally closed to normally open, the connection state between the sampling circuit power supply and the adjustable resistor W end of the digital potentiometer is converted from disconnected to connected, and the connection state between the ground end and the first resistor is converted from disconnected to connected, the adjustable resistor W end and L end of the digital potentiometer are connected to the sampling circuit power supply and the first resistor to form a linear voltage divider circuit, and the sampling port obtains R ADC = (R1 / (R1+R))*VCC voltage value, and then the equivalent resistance R of the terminal resistor in the actual circuit is obtained by conversion, where R1 represents the resistance of the first resistor, R ADC Indicates the voltage value of the sampling port, VCC is the power supply of the sampling circuit.

[0023] Compared with the prior art, the beneficial effects of the present invention are: optimizing the circuit design, making the circuit simple and efficient, using fewer devices, low cost, and small space occupation; the circuit design is reasonable and has strong compatibility, and can be well applied to 485 communication circuits and CAN communication circuits, etc.; on this basis, the corresponding control method is also optimized, and a manual matching mode or an automatic matching mode can be selected according to actual needs. The matching control process is reasonable and does not affect the data transmission and reception of the communication circuit. On the basis of saving labor costs, it also effectively improves work efficiency, which is beneficial to the debugging and maintenance of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the circuit principle of an embodiment of the present invention;

[0025] Figure 2 It is a circuit structure diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, this embodiment provides a communication terminal resistance matching circuit for an air-conditioning system, including: an air-conditioning controller MCU, an analog electronic switch U1, a digital potentiometer U2, a first resistor R1, and an anti-short-circuit current limiting protection circuit. The analog electronic switch U1 includes a first switch and a second switch. The normally closed end NC1 of the first switch and the normally closed end NC2 of the second switch are respectively connected to the first output end B / L and the second output end A / H of the communication interface J1. The common end COM1 of the first switch and the common end COM2 of the second switch are respectively connected to the two ends of the adjustable resistor of the digital potentiometer U2. The normally open end NO1 of the first switch is connected to the first resistor R1 through the first resistor. R1 is grounded GND, and the normally open end NO2 of the second switch is connected to the sampling circuit power supply VCC; the sampling port MCU_ADC of the air-conditioning controller MCU is connected between the first resistor R1 and the digital potentiometer U2. After the normally open end NO1 of the first switch of the analog electronic switch U1 and the normally open end NO2 of the second switch are closed, the sampling port MCU_ADC of the air-conditioning controller MCU measures the voltage value of the connection midpoint between the first resistor R1 and the digital potentiometer U2, and calculates and confirms the adjustable resistance value of the digital potentiometer U2 through the air-conditioning controller MCU; the first switch and the second switch are respectively connected to the anti-short-circuit current limiting protection circuit.

[0028] The communication interface J1 of this embodiment refers to a communication interface for connecting to a communication circuit, such as a 485 communication circuit and a CAN communication circuit. The analog electronic switch U1 of this embodiment includes two switches, namely a first switch and a second switch. Figure 1 As shown in U1_1 and U1_2, the first switch includes a normally open terminal NO1, a common terminal COM1, and a normally closed terminal NC1, and the second switch includes a normally open terminal NO2, a common terminal COM2, and a normally closed terminal NC2. In this embodiment, the first switch and the second switch need to realize simultaneous on / off control, that is, realize the normally open or normally closed state conversion at the same time.

[0029] In this embodiment, the control pin IN1 of the first switch and the control pin IN2 of the second switch are electrically connected to the control pin MCU_DO of the air-conditioning controller MCU. The air-conditioning controller MCU sends a control signal to control the synchronous on and off of the first switch and the second switch, so as to facilitate the synchronous control of state transition through the air-conditioning controller MCU. The synchronous on and off is synchronous conduction or synchronous shutdown.

[0030] In the default state, the common terminal COM1 of the first switch and the normally closed terminal NC1 of the present embodiment are in a closed state, and the common terminal COM2 of the second switch and the normally closed terminal NC2 are in a closed state; if the terminal resistance value needs to be detected, the air-conditioning controller MCU sends a control signal to the control pin IN1 of the first switch and the control pin IN2 of the second switch to control the common terminal COM1 of the first switch and the normally open terminal N01 to be converted into a closed state, and controls the common terminal COM2 of the second switch and the normally open terminal N02 to be converted into a closed state. After the state conversion, the voltage value of the connection midpoint between the first resistor R1 and the digital potentiometer U2 is detected through the sampling port MCU_ADC of the air-conditioning controller MCU.

[0031] like Figure 1 and Figure 2 As shown, the common terminal COM1 of the first switch and the common terminal COM2 of the second switch in this embodiment are respectively connected to the L end and the W end of the adjustable resistor of the digital potentiometer U2, so that the W end and the L end of the adjustable resistor of the digital potentiometer U2 and the first resistor R1 are connected to the power supply to form a linear voltage divider circuit, and then the equivalent resistance value in the communication circuit can be obtained by conversion.

[0032] The digital potentiometer U2 of this embodiment is connected to the communication pins MCU_SDA and MCU_SCL of the air-conditioning controller MCU through the I2C serial bus to realize the adjustment of the adjustable resistance value of the digital potentiometer U2, thereby providing a good basis for setting the terminal resistance matching mode through the touch screen, and realizing automatic matching of the terminal resistance through the air-conditioning controller MCU, which facilitates the debugging and maintenance of the circuit.

[0033] like Figure 1 and Figure 2 As shown, the short-circuit current-limiting protection circuit of this embodiment includes a second resistor R2, a third resistor R3, a first suppressor diode D1, a second suppressor diode D2, and a third suppressor diode D3. One end of the second resistor R2 is connected to the common terminal COM2 of the second switch, and the other end of the second resistor R2 is respectively connected to one end of the first suppressor diode D1, one end of the second suppressor diode D2, and the second output terminal A / H of the communication interface J1. The other end of the first suppressor diode D1 is grounded. One end of the third resistor R3 is connected to the common terminal COM1 of the first switch, and the other end of the third resistor R3 is respectively connected to the other end of the second suppressor diode D2, one end of the third suppressor diode D3, and the first output terminal B / L of the communication interface. The other end of the third suppressor diode D3 is grounded. Among them, the second resistor R2 and the third resistor R3 are short-circuit current-limiting resistors, and the first suppressor diode D1, the second suppressor diode D2, and the third suppressor diode D3 are used to implement protection for the communication circuit, such as overcurrent protection, surge suppression, and electrostatic protection.

[0034] This embodiment further provides a method for controlling a communication terminal resistance matching circuit of an air-conditioning system, which is used to control the communication terminal resistance matching circuit of the air-conditioning system as described above, and includes the following steps:

[0035] Step S1, setting the operating mode of the air conditioning system communication terminal resistance matching circuit through the touch screen. If it is set to manual matching mode, jump to step S2; if it is set to automatic matching mode, jump to step S3;

[0036] Step S2, setting the resistance value of the digital potentiometer U2 by detecting the input signal of the touch screen;

[0037] Step S3, automatically detecting the terminal resistance value after networking, and adjusting the digital potentiometer U2 according to the preset terminal resistance setting value to achieve the setting and adjustment of the terminal resistance value. The terminal resistance value after networking refers to the actual terminal resistance value detected after networking.

[0038] In step S1 of this embodiment, the operating mode of the terminal resistance matching circuit can be directly set through the touch screen, including manual matching mode and automatic matching mode. When the manual matching mode is selected, the resistance value of the digital potentiometer U2 is set. When the automatic matching mode is selected, after setting the terminal resistance value, the communication terminal resistance adjustment mode is entered, and the terminal resistance value of the networked circuit is automatically detected. The digital potentiometer U2 is adjusted according to the pre-set terminal resistance setting value to automatically match the terminal resistance value of the network and adjust it to the terminal resistance setting value. The terminal resistance setting value refers to the pre-set terminal resistance value, which can be customized and adjusted according to actual conditions and needs.

[0039] In step S2 of this embodiment, the communication terminal resistance adjustment page is first entered, and the terminal resistance matching mode is set to manual matching mode through the touch screen, and the corresponding terminal resistance value is set. After detecting and confirming the setting of the corresponding terminal resistance value, the terminal resistance setting value on the touch screen is sent to the air conditioning controller MCU, and the communication pins MCU_SDA and MCU_SCL of the air conditioning controller MCU are connected through I 2 The C serial bus sends the terminal resistance setting value to the serial bus pins (including SDA and SCL) of the digital potentiometer U2, and adjusts the adjustable resistors L and W of the digital potentiometer U2 to the terminal resistance setting value.

[0040] Step S3 of this embodiment includes the following sub-steps:

[0041] Step S301: First, enter the communication terminal resistance adjustment page, set the terminal resistance matching mode to automatic matching mode through the touch screen, and after confirmation, set the corresponding automatic matching terminal resistance setting value;

[0042] Step S302: Before the communication starts, the L and W ends of the adjustable resistors of the digital potentiometer U2 are first adjusted to the set terminal resistance setting value, and then the equivalent resistance value of the terminal resistance in the actual circuit after networking is detected and calculated. The terminal resistance setting value and the equivalent resistance value in the actual circuit are compared by the air-conditioning controller MCU, and the adjustable resistance of the digital potentiometer U2 is adjusted until the error between the terminal resistance setting value and the equivalent resistance value is within the allowable range. It is then determined that the match is successful, and preparation for communication begins. The first switch and the second switch of the analog electronic switch U1 are converted from normally open to normally closed to perform data communication. The allowable range refers to the error threshold between the terminal resistance setting value and the equivalent resistance value, which can be customized and adjusted according to actual conditions and accuracy requirements. The adjustable resistance of the digital potentiometer U2 is preferably adjusted with the difference between the terminal resistance setting value and the equivalent resistance value as a reference. Each adjustment uses the difference between the current terminal resistance setting value and the equivalent resistance value as the adjustment step, thereby enabling rapid and efficient automatic matching.

[0043] Step S303 , during the communication circuit transceiver conversion process of the communication interface J1 , step S302 is repeated to automatically match the terminal resistance, and after the matching is completed, the communication mode is returned to by simulating the switching of the electronic switch U1 .

[0044] It is worth noting that when the communication circuit switches between the transmitting and receiving states, a certain switching time is required to enable the communication to transition to a stable state. Therefore, when the present embodiment detects that the communication circuit of the communication interface J1 enters the transceiver conversion state, the air conditioner controller MCU controls the terminal resistance matching circuit to enter the automatic matching mode, that is, during the transceiver conversion process of the communication circuit, step S302 is automatically repeated to perform automatic matching of the terminal resistance. Because the transceiver state conversion time of the communication circuit can reach tens of milliseconds or longer, which is much longer than the automatic matching time required by the terminal resistance matching circuit of the present embodiment, that is, during the conversion time of the transceiver conversion process of the communication circuit, the electronic analog switch of the analog electronic switch U1 of the present embodiment completes the conversion between the normally open end and the normally closed end. The speed of the electronic analog switch U1 is generally in the nanosecond level, and the sampling speed of the analog voltage of the air conditioner controller MCU is generally in the microsecond level. Therefore, the automatic matching of the terminal resistance matching circuit of the present embodiment during the transceiver conversion process of the communication circuit does not affect the data transmission and reception of the communication circuit, and can also reasonably utilize the conversion time of the communication circuit to complete the automatic matching process of the terminal resistance in real time and efficiently. The design is reasonable and efficient, does not affect the normal operation of the communication mode, and does not require additional time for debugging and matching. This is particularly important for the production and debugging process of the equipment.

[0045] In step S302 of this embodiment, the process of detecting and calculating the equivalent resistance value of the terminal resistor in the actual circuit after networking is as follows: the first switch and the second switch of the analog electronic switch U1 are switched from normally closed to normally open, the connection state between the sampling circuit power supply VCC and the adjustable resistor W end of the digital potentiometer U2 is switched from disconnected to connected, and the connection state between the ground end and the first resistor R1 is switched from disconnected to connected, the adjustable resistor W end and L end of the digital potentiometer U2 are connected to the first resistor R1 to form a linear voltage divider circuit after being connected to the sampling circuit power supply VCC, and the sampling port MCU_ADC obtains R ADC = (R1 / (R1+R))*VCC voltage value, and then the equivalent resistance R of the terminal resistance in the actual circuit is obtained by conversion, where R1 represents the resistance value of the first resistor R1, R ADC Indicates the voltage value of the sampling port MCU_ADC.

[0046] In summary, this embodiment optimizes the design of the circuit, making the circuit simple and efficient, using fewer devices, low cost, and small space. The circuit design is reasonable and compatible, and can be well applied to 485 communication circuits and CAN communication circuits, etc. On this basis, the corresponding control method is also optimized, and manual matching mode or automatic matching mode can be selected according to actual needs. The matching control process is reasonable and does not affect the data transmission and reception of the communication circuit. On the basis of saving labor costs, it also effectively improves work efficiency, which is beneficial to the debugging and maintenance of the circuit.

[0047] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A communication terminal resistance matching circuit for an air conditioning system, characterized in that: include: An air conditioning controller, an analog electronic switch, a digital potentiometer, a first resistor, and an anti-short-circuit current-limiting protection circuit. The analog electronic switch includes a first switch and a second switch. The normally closed end of the first switch and the normally closed end of the second switch are respectively connected to the first output end and the second output end of the communication interface. The common end of the first switch and the common end of the second switch are respectively connected to the two ends of the adjustable resistor of the digital potentiometer. The normally open end of the first switch is grounded through the first resistor, and the normally open end of the second switch is connected to a sampling circuit power supply. The sampling port of the air conditioning controller is connected between the first resistor and the digital potentiometer. After the normally open end of the first switch and the normally open end of the second switch are closed, the sampling port of the air conditioning controller measures the voltage value at the connection midpoint between the first resistor and the digital potentiometer, and the air conditioning controller calculates and confirms the adjustable resistance value of the digital potentiometer. The first switch and the second switch are respectively connected to the anti-short-circuit current-limiting protection circuit.

2. The air conditioning system communication terminal resistance matching circuit according to claim 1, characterized in that: The control pin of the first switch and the control pin of the second switch are electrically connected to the control pin of the air-conditioning controller, and the air-conditioning controller sends a control signal to control the first switch and the second switch to be turned on and off synchronously.

3. The air conditioning system communication terminal resistance matching circuit according to claim 2, characterized in that: In a default state, the common end and the normally closed end of the first switch are in a closed state, and the common end and the normally closed end of the second switch are in a closed state; if it is necessary to detect the resistance value of the terminal resistor, the air-conditioning controller sends a control signal to the control pin of the first switch and the control pin of the second switch to control the common end and the normally open end of the first switch to be converted to a closed state, and controls the common end and the normally open end of the second switch to be converted to a closed state. After the state conversion, the voltage value of the connection midpoint between the first resistor and the digital potentiometer is detected through the sampling port of the air-conditioning controller.

4. The air conditioning system communication terminal resistance matching circuit according to claim 1, characterized in that: The common end of the first switch and the common end of the second switch are respectively connected to the L end and the W end of the adjustable resistor of the digital potentiometer.

5. The communication terminal resistance matching circuit of the air conditioning system according to any one of claims 1 to 4, characterized in that: The digital potentiometer is connected to the 2 The C serial bus is connected to the communication pin of the air-conditioning controller to adjust the resistance value of the adjustable resistor of the digital potentiometer.

6. The communication terminal resistance matching circuit for an air conditioning system according to any one of claims 1 to 4, characterized in that: The short-circuit current limiting protection circuit includes a second resistor, a third resistor, a first suppression diode, a second suppression diode and a third suppression diode. One end of the second resistor is connected to the common end of the second switch, and the other end of the second resistor is respectively connected to one end of the first suppression diode, one end of the second suppression diode and the second output end of the communication interface. The other end of the first suppression diode is grounded. One end of the third resistor is connected to the common end of the first switch, and the other end of the third resistor is respectively connected to the other end of the second suppression diode, one end of the third suppression diode and the first output end of the communication interface. The other end of the third suppression diode is grounded.

7. A control method for a communication terminal resistance matching circuit of an air conditioning system, characterized in that: Used to control the communication terminal resistance matching circuit of the air conditioning system according to any one of claims 1 to 6, and comprising the following steps: Step S1, setting the operating mode of the air conditioning system communication terminal resistance matching circuit through the touch screen. If it is set to manual matching mode, jump to step S2; if it is set to automatic matching mode, jump to step S3; Step S2, setting the resistance value of the digital potentiometer by detecting the input signal of the touch screen; Step S3, automatically detecting the terminal resistance value after networking, and adjusting the digital potentiometer according to the preset terminal resistance setting value to achieve setting and adjustment of the terminal resistance value.

8. The control method of the communication terminal resistance matching circuit of the air conditioning system according to claim 7, characterized in that: In the step S2, after the corresponding terminal resistance value is detected and confirmed, the terminal resistance setting value on the touch screen is sent to the air conditioning controller, and the communication pin of the air conditioning controller is connected via I 2 The C serial bus sends the terminal resistance setting value to the serial bus pin of the digital potentiometer, and adjusts the adjustable resistor L end and W end of the digital potentiometer to the terminal resistance setting value.

9. The control method of the communication terminal resistance matching circuit of the air conditioning system according to claim 7, characterized in that: The step S3 includes the following sub-steps: Step S301, setting and confirming the corresponding automatically matched terminal resistance setting value through the touch screen; Step S302: Before communication begins, the adjustable resistors L and W of the digital potentiometer are first adjusted to the set terminal resistance values. Then, the equivalent resistance value of the terminal resistance in the actual circuit after networking is detected and calculated. The air conditioner controller then compares the terminal resistance set value with the equivalent resistance value in the actual circuit and adjusts the adjustable resistance of the digital potentiometer until the error between the terminal resistance set value and the equivalent resistance value is within an allowable range. This determines that the match is successful, and communication preparation begins. The first and second switches of the analog electronic switch are switched from normally open to normally closed to initiate data communication. Step S303, during the communication circuit transceiver conversion process of the communication interface, repeat step S302 to automatically match the terminal resistance, and after the matching is completed, return to the communication mode by switching the analog electronic switch.

10. The control method of the communication terminal resistance matching circuit of the air conditioning system according to claim 9, characterized in that: In step S302, the process of detecting and calculating the equivalent resistance value of the terminal resistor in the actual circuit after networking is as follows: the first switch and the second switch of the analog electronic switch are switched from normally closed to normally open, the connection state between the sampling circuit power supply and the adjustable resistor W end of the digital potentiometer is switched from disconnected to connected, and the connection state between the ground end and the first resistor is switched from disconnected to connected, the adjustable resistor W end and L end of the digital potentiometer are connected to the sampling circuit power supply to form a linear voltage divider circuit, and the sampling port obtains R ADC = (R1 / (R1+R))*VCC voltage value, and then the equivalent resistance R of the terminal resistor in the actual circuit is obtained by conversion, where R1 represents the resistance of the first resistor, R ADC Indicates the voltage value of the sampling port, VCC is the power supply of the sampling circuit.

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