Device for self-checking data line by using charger

Abstract

The utility model discloses a device for self-checking a data line by using a charger. The device comprises a power supply unit, a power supply conversion unit, a bidirectional conversion unit, a first interface and a second interface, the power unit is connected with the power conversion unit; the power conversion unit is connected with the first interface; the power supply unit is connected with the bidirectional conversion unit; the bidirectional conversion unit is connected with the second interface; two ends of the data line are respectively connected with the first interface and the second interface; the power conversion unit is connected with the bidirectional conversion unit. By implementing the device provided by the utility model, self-inspection can be carried out on the wire harness in charging connection.

Description

Technical Field

[0001] This utility model relates to the field of data cable technology, and in particular to a device for self-testing data cables using a charger. Background Technology

[0002] Most chargers and adapters on the market today, regardless of whether they have USB 1A, USB 2C, or other types of USB ports, primarily function only to provide power output to mobile phones and other devices. The USB 1A or USB 2C ports on these devices typically only have output capabilities and lack input detection. This means they cannot assess the status of the connected data cable, such as internal resistance and voltage drop, leading to a series of problems. For example, due to the wide variation in the quality of data cables on the market—prices can differ by hundreds of times from low-quality to high-quality—users often find it difficult to determine whether the data cable they are using is suitable for high-power charging. When high-power chargers (35W to 300W) are used with low-quality data cables, not only will charging efficiency be low, but there is also a risk of fire due to overheating. In some cases, a faulty data cable may even prevent the charging process or damage the device being charged, such as a smartphone, tablet, or laptop.

[0003] Therefore, it is necessary to design a new device to perform self-testing on the wiring harness of the charging connection. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a device that utilizes a charger self-test data cable.

[0005] To solve the above-mentioned technical problems, the purpose of this utility model is achieved through the following technical solution: A device utilizing a charger self-test data cable is provided, comprising: a power supply unit, a power conversion unit, a bidirectional conversion unit, a first interface, and a second interface; the power supply unit is connected to the power conversion unit; the power conversion unit is connected to the first interface; the power supply unit is connected to the bidirectional conversion unit; the bidirectional conversion unit is connected to the second interface; both ends of the data cable are respectively connected to the first interface and the second interface; the power conversion unit is connected to the bidirectional conversion unit.

[0006] The further technical solution is as follows: the power supply unit includes an AD-DC charger.

[0007] The further technical solution is as follows: the power conversion unit includes a first BUCK chip with a fast charging protocol integrated within it.

[0008] The further technical solution is as follows: the bidirectional protocol control unit includes a second BUCK chip with integrated PD bidirectional protocol and a switching device, the second BUCK chip is connected to the switching device, the first BUCK chip and the second interface respectively; the switching device is connected to the first BUCK chip and the second interface respectively.

[0009] The further technical solution is as follows: the first interface includes a TYPE-C interface.

[0010] The further technical solution is as follows: the second interface includes a TYPE-C interface.

[0011] The further technical solution includes: a control unit and a display module; the control unit is connected to the power conversion unit and the display module respectively.

[0012] The further technical solution is as follows: the switching device includes a MOSFET.

[0013] The further technical solution is as follows: the display module includes a display screen.

[0014] The further technical solution is as follows: the first BUCK chip is connected to the first interface through a resistor.

[0015] The advantages of this invention compared to existing technologies are as follows: This invention integrates a power supply unit, a power conversion unit, a bidirectional conversion unit, a control unit, a display module, a first interface, and a second interface. When the user inserts both ends of the data cable into the first and second interfaces respectively, the power supply unit supplies power to the system and adjusts the voltage through the power conversion unit to ensure compatibility with connected devices. Simultaneously, the bidirectional conversion unit coordinates the fast charging protocol to achieve optimal power transmission. The control unit monitors the entire process and assesses the data cable quality by detecting the voltage difference between input and output. The results are presented intuitively to the user through the display module, enabling self-testing of the charging connection harness.

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic block diagram of a device utilizing a charger self-test data cable provided for an embodiment of this utility model;

[0019] Figure 2 A detailed circuit diagram of a device utilizing a charger self-test data cable is provided for an embodiment of this utility model.

[0020] Figure 3 A schematic diagram of the principle of a device utilizing a charger self-test data cable provided in an embodiment of this utility model;

[0021] Explanation of the markings in the image:

[0022] 10. Power supply unit; 20. Power conversion unit; 30. Bidirectional conversion unit; 40. Control unit; 50. Display module; 60. First interface; 70. Second interface. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0024] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0025] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0027] Most chargers and adapters currently lack input detection functionality for the connected data cable, making it impossible to assess the cable's quality and electrical performance. Due to the inconsistent quality of data cables on the market, users struggle to determine their suitability for high-power charging, potentially leading to inefficient charging or device damage. Using a low-quality data cable with a high-power charger can cause overheating or even fire hazards. Devices lacking input detection functionality cannot effectively avoid these safety risks, impacting the reliability and safety of the charging process.

[0028] To address this, this utility model provides a data cable self-testing device that performs self-testing on the charging connection harness, ensuring a comprehensive high-performance charging experience that enhances safety, optimizes charging efficiency, and prevents overheating and fire accidents, thus achieving fast and stable safe charging.

[0029] Specifically, the device provides a stable power supply through the power supply unit 10 and the power conversion unit 20, providing a voltage signal for the detection process. The bidirectional conversion unit 30 coordinates the current flow and ensures circuit closure through a switching element, initiating the self-test process to detect the connection performance of the data cable. The power conversion unit 20 evaluates the charging capability and performance of the data cable based on the voltage difference in the closed loop and in accordance with known standards. The performance data is transmitted to the display module 50 through the control unit 40, providing real-time feedback and displaying the health status and charging efficiency of the data cable. This self-test process ensures stable charging connection, optimizes charging efficiency, reduces overheating and fire hazards, and improves charging safety and reliability.

[0030] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0031] Please see Figure 1 , Figure 1 This is a schematic block diagram of a device for self-testing a data cable using a charger, which can be used in a charger to perform self-testing on the charging connection harness, ensuring a comprehensive high-performance charging experience that enhances safety, optimizes charging efficiency, and prevents overheating and fire accidents, thus achieving fast and stable safe charging.

[0032] The aforementioned device utilizing a charger self-test data cable includes: a power supply unit 10, a power conversion unit 20, a bidirectional conversion unit 30, a control unit 40, a display module 50, a first interface 60, and a second interface 70; the power supply unit 10 is connected to the power conversion unit 20; the power conversion unit 20 is connected to the first interface 60; the power supply unit 10 is connected to the bidirectional conversion unit 30; the bidirectional conversion unit 30 is connected to the second interface 70; the control unit 40 is connected to both the power conversion unit 20 and the display module 50; the two ends of the data cable are connected to the first interface 60 and the second interface 70, respectively; the power conversion unit 20 is connected to the bidirectional conversion unit 30.

[0033] In this embodiment, the data cable has two main forms:

[0034] This is a dual-ended Type-C data cable, suitable for connecting two devices that support the Type-C interface.

[0035] This data cable has a TYPE-A interface on one end and a TYPE-C interface on the other, making it suitable for connecting traditional USB devices with newer TYPE-C devices.

[0036] The device in this embodiment is based on the following principle:

[0037] During charging, the protocol chip is responsible for monitoring and managing voltage and current. For dual-ended Type-C interface data cables, when both ends are connected, the protocol chip can provide a specific voltage (such as 5V or 9V) and monitor the loop status transmitted through the cable to the other end and back to the protocol chip. This process involves the following steps:

[0038] First, such as Figure 3 As shown, the protocol chip detects whether a complete loop is formed between terminals A and B. The self-test program will only be initiated once the loop is confirmed to be established.

[0039] Once the circuit is established, the system will select a fixed current value (e.g., within the range of 0.5 to 3A) for testing and apply the corresponding voltage (e.g., 5V).

[0040] Since a fixed current value is chosen, according to Ohm's law (U=I*R), the resistance of the wire harness can be calculated by measuring the voltage difference between terminals A and B. Different wire harness qualities will result in different resistance values, thus affecting the final voltage at terminal B.

[0041] By comparing the voltage difference between terminals A and B or by directly measuring the resistance, the protocol IC can assess the condition of the harness and determine whether it is suitable for the current charging requirements.

[0042] Specifically, the quality of a wire harness is judged based on its maximum operating current capacity and corresponding internal resistance, typically expressed using the AWG (American Wire Gauge) standard. The following are specific evaluation methods for different grades of wire harnesses:

[0043] Using an AWG17 specification wire harness, the designed operating current exceeds 4.1A, and the internal resistance is 16.3Ω / Km. For a one-meter-long wire harness, under ideal conditions of 5V / 3A, the voltage measured at terminal B should be close to 4.951V or higher. This indicates that the wire harness has low resistance characteristics and is the optimal choice.

[0044] For AWG18 specification wire harnesses, the operating current range is above 3.2A, and the internal resistance is 21.4Ω / Km. Under the same conditions, if the voltage measured at terminal B is between 4.938V and 4.950V, the wire harness is considered to be of ordinary grade.

[0045] The AWG19 specification wire harness is suitable for applications with a working current of 2.6A or higher, and has an internal resistance of 26.9Ω / Km. If the voltage at terminal B is lower than 4.919V or between 4.919V and 4.937V, it indicates that the wire harness is of poor quality and may not be suitable for high-efficiency charging requirements.

[0046] In summary, the device in this embodiment achieves effective self-testing of the charging harness through precise voltage and current control and impedance measurement technology, ensuring a safe and efficient charging experience. Furthermore, with clear evaluation criteria, users can easily identify the quality level of the charging harness and select the most suitable charging accessory for their device.

[0047] Specifically, the power supply unit 10 receives AC 96V to 240V input and converts it into DC power suitable for subsequent circuits. The power supply unit 10 is directly connected to the power conversion unit 20, providing it with a stable DC power supply.

[0048] The power conversion unit 20 is responsible for converting the DC voltage provided by the power unit 10 into different levels of output voltage to meet the requirements of different fast charging protocols (such as PD, QC, AFCS, FCP, SCP, PPS, etc.). It also implements a handshake protocol with external devices to determine the optimal charging parameters.

[0049] The power conversion unit 20 is connected to the power unit 10 and also to the first interface 60 (i.e., TYPE-C1) to receive control signals and feedback information from external devices.

[0050] The bidirectional conversion unit 30 allows bidirectional flow of data and power at both ends of the data line, supporting the use of the second interface 70 as an input or output. This unit is connected to the power supply unit 10 on one side and to the second interface 70 (i.e., TYPE-C2) on the other, enabling bidirectional transmission of power and data.

[0051] The control unit 40 is connected to the power conversion unit 20 and the display module 50 respectively, so as to acquire status information and display the results to the user.

[0052] The display module 50 is used to intuitively present the system's working status or test results to the user, such as using LEDs to indicate the quality of the data cable. The display module 50 is connected to the control unit 40, receives status updates from the control unit 40, and adjusts the display content accordingly.

[0053] The first interface 60 serves as one of the interfaces between the system and external devices, primarily for receiving power requests and handshake protocols from external devices. It is connected to the power conversion unit 20 to transmit signals related to the handshake protocol.

[0054] In addition to serving as an output port, the second interface 70 also has bidirectional operation capability and can act as an input port under certain conditions. Connected to the bidirectional conversion unit 30, it enables bidirectional flow of power and data.

[0055] The data cable physically connects the first interface 60 and the second interface 70, carrying power transmission and the signal exchange required for the handshake protocol. One end is connected to the first interface 60, and the other end is connected to the second interface 70, forming a complete power and data channel.

[0056] In one embodiment, the power supply unit 10 described above includes an AC-DC charger. In this embodiment, the power supply unit 10 primarily consists of an AC-DC charger designed to accept a wide range of AC input voltages, i.e., AC 96V to 240V. This broad input voltage range makes the charger suitable for different power standards worldwide. The main function of the AC-DC charger is to convert AC power to DC power, providing the necessary power support for the entire self-test device.

[0057] AC-DC chargers pass through Figure 2 The connection point marked VIN is connected to the entire device. This connection point is the energy entry point for the entire circuit, ensuring that power from the external power grid can be safely and stably transmitted to subsequent modules. To achieve efficient energy conversion, the AC-DC charger employs advanced power conversion technologies, such as using a high-frequency switching mode power supply to improve efficiency and reduce size.

[0058] In one embodiment, please refer to Figure 2The aforementioned power conversion unit 20 includes a first BUCK chip with integrated fast charging protocols. This first BUCK chip not only performs buck (i.e., reduces the output voltage from a higher input voltage) function, but also has built-in support for various fast charging protocols, such as PD (Power Delivery), QC (Quick Charge), AFCS (Adaptive Fast Charging System), FCP (Fast Charging Protocol), SCP (Super Charge Pump), and PPS (Programmable Power Supply). This means that when the TYPE-C1 or TYPE-C2 port is connected to a device that supports these protocols, it can automatically identify the supported protocols and negotiate the most suitable charging parameters, such as voltage and current levels.

[0059] Specifically, when an external power source is connected to VIN, it is converted into a DC voltage suitable for system operation by an AC-DC charger. This DC voltage is then passed to the first BUCK chip in the power conversion unit 20. Based on the requirements of the actual application scenario, the first BUCK chip adjusts its output voltage to an appropriate value to meet the requirements of the downstream load. If the connected device supports a fast charging protocol, the first BUCK chip will communicate with it via a TYPE-C interface to set the optimal charging conditions according to a mutually agreed-upon protocol.

[0060] During the self-test process, the first BUCK chip also participates in building the test circuit to help measure the resistance of the data line and thus evaluate its quality.

[0061] In one embodiment, please refer to Figure 2 The aforementioned bidirectional protocol control unit 30 includes a second BUCK chip with integrated PD bidirectional protocol and a switching element. The second BUCK chip is connected to the switching element, the first BUCK chip, and the second interface 70, respectively. The switching element is connected to the first BUCK chip and the second interface 70, respectively.

[0062] In this embodiment, the second BUCK chip has built-in support for multiple PD bidirectional protocols, enabling it to handshake with different external devices and determine optimal charging parameters. It also features voltage conversion capabilities, adjusting the output voltage based on the handshake result to meet the needs of different devices. This achieves bidirectional power transmission, meaning it can not only act as a power output terminal to supply power to other devices but also receive power from external devices when needed.

[0063] The second BUCK chip is connected to the switching device, and determines the direction and path of power flow by controlling the state of the switching device.

[0064] The second BUCK chip is connected to the first BUCK chip to facilitate information exchange and coordination between the two, ensuring the stable operation of the entire system.

[0065] The second BUCK chip is directly connected to the second interface 70 (type-c2), allowing it to directly manage the power supply to or obtain power from external devices.

[0066] The second BUCK chip controls the switching of states to selectively connect or disconnect various parts of the circuit, thereby achieving directional control of power flow. It supports a bidirectional operating mode, allowing for flexible adjustment of power flow direction according to actual needs.

[0067] The second BUCK chip is connected to both the first BUCK chip and the second interface 70, forming a complete power path from input to output or in reverse. Signal cascading exists between the second BUCK chip and the first BUCK chip, ensuring the accuracy and timeliness of the switching action.

[0068] When the system is in self-test mode, the second BUCK chip is responsible for setting appropriate test conditions and establishing the necessary test loops by controlling the switches. For example, during the data line quality test, the second BUCK chip instructs the switches to close specific circuit branches, forming a loop between VOUT1 and VOUT2. At this time, the quality of the data line can be evaluated by measuring the voltage difference between the two points. Afterwards, the first BUCK chip sends the processed results to the control unit 40, which is then presented to the user by the display module 50.

[0069] In one embodiment, please refer to Figure 2 The first interface 60 mentioned above includes a TYPE-C interface, specifically a type-c1 interface.

[0070] In one embodiment, please refer to Figure 2 The second interface 70 mentioned above includes a TYPE-C interface, specifically a type-c2 interface.

[0071] The first interface, 60, is a Type-C1 interface used to receive power input or data transfer from an external power source. This interface is compatible with the USB Power Delivery (PD) protocol and supports fast charging and other advanced features.

[0072] The second interface 70 is a Type-C2 interface, responsible for providing power output or exchanging data with external devices. Similarly, it conforms to the Type-C standard and is compatible with various types of terminal devices, ensuring a wide range of applications.

[0073] In one embodiment, please refer to Figure 2The aforementioned display module 50 includes a display screen.

[0074] In one embodiment, please refer to Figure 2 The aforementioned switching device includes MOSFET Q1. A MOSFET is a field-effect transistor that acts as a switch in a circuit, controlling the selection of the current path to achieve switching between different operating modes.

[0075] In one embodiment, please refer to Figure 2 The aforementioned display module 50 also includes LED lights.

[0076] In one embodiment, please refer to Figure 2 The aforementioned first BUCK chip is connected to the first interface 60 via a resistor.

[0077] The display screen visually presents system status, settings options, and other information to the user. This allows users to easily monitor and manage the device's operating parameters.

[0078] LED lights, as auxiliary indicator devices, can convey key status information, such as power connection status and charging progress, in a simple and direct way. This visual feedback is crucial for improving the user experience.

[0079] Specifically, please refer to Figure 2 The first BUCK chip is connected to the first interface 60 via resistor RCS1; the second BUCK chip is connected to the second interface 70 via resistor RCS2; and the MOSFET Q1 is connected to the second interface 70 via resistor RS.

[0080] The BUCK chip is connected to the first interface 60 (i.e., type-C1) via resistor RCS1. Resistor RCS1 serves as a current limiter here, protecting the circuit from overload damage while also helping to stabilize the input voltage and ensure the normal operation of the BUCK chip.

[0081] The BUCK-BOOST converter connects to the second interface 70 (i.e., type-C2) via resistor RCS2. Similarly, resistor RCS2 helps to adjust and stabilize the output voltage, ensuring the safety and reliability of power supply to external devices.

[0082] The MOSFET Q1 is connected to the second interface 70 via a resistor RS. Resistor RS not only helps control the operating state of the MOSFET but also provides necessary electrical isolation to prevent potential short circuits or other abnormal conditions from affecting the entire system.

[0083] Please see Figure 2 The microcontroller in the diagram refers to control unit 40. The workflow of the entire device is as follows:

[0084] The charger uses an AC96V~240V AC-DC power input, indicated by VIN. It connects to the Type-C1 interface via a first BUCK chip that integrates fast charging protocols (such as PD, QC, AFCS, FCP, SCP, PPS, etc.) to enable fast charging and power transfer management for connected devices. The Type-C2 interface connects to the first BUCK chip via specific pins and supports bidirectional power transfer.

[0085] When a user plugs the charging cable into a Type-C1 or Type-C2 port, the built-in protocol's first BUCK chip detects this action and initiates a protocol handshake with the connected device (such as a mobile phone or computer). During the handshake, the protocol chip negotiates optimal charging parameters based on the other party's support, thereby controlling the AC-DC converter to output appropriate voltage and current to the load device.

[0086] To verify the quality of the data cable, an automatic testing function was designed. When a data cable with both ends having TYPE-C interfaces is connected to both Type-C1 and Type-C2 simultaneously, the self-test process is initiated:

[0087] VOUT1 connects to pins 3, 4, 11, and 12 of type-c1 via data lines to pins 3, 4, 13, and 14 of type-c2, and finally to VOUT2.

[0088] The first BUCK chip sends a level signal to activate MOSFET Q1, causing it to conduct and form a short-circuit path to ground.

[0089] At this point, current can flow back to the VOUT2 terminal of the first BUCK chip through the ground wire of VOUT2, while VOUT1 is connected to the other terminal of the first BUCK chip. This forms a complete closed circuit, allowing the system to measure the voltage difference between VOUT1 and VOUT2.

[0090] Using the measured voltage drop and known resistance value, the quality level of the data cable can be calculated, including best, average, or poor.

[0091] Finally, the judgment result is transmitted to the microcontroller through the I2C communication interface (SCL and SDA) on the first BUCK chip. The microcontroller then controls the corresponding I / O pin of the LED or display screen to intuitively display the quality status of the data line.

[0092] The device in this embodiment can not only effectively manage power transmission, but also automatically evaluate the quality of data lines without affecting normal use, providing convenience to users while ensuring the safety and reliability of the system.

[0093] In this embodiment, the first BUCK chip is of the type, but not limited to, SW3561; the microcontroller is of the type, but not limited to, MC9959; and the second BUCK chip is of the type, but not limited to, SW3561.

[0094] The aforementioned device utilizing a charger self-testing data cable integrates a power supply unit 10, a power conversion unit 20, a bidirectional conversion unit 30, a control unit 40, a display module 50, a first interface 60, and a second interface 70. When the user inserts both ends of the data cable into the first interface 60 and the second interface 70 respectively, the power supply unit 10 supplies power to the system, and the power conversion unit 20 adjusts the voltage to ensure compatibility with connected devices. Simultaneously, the bidirectional conversion unit 30 coordinates the fast charging protocol to achieve optimal power transmission. The control unit 40 monitors the entire process and evaluates the data cable quality by detecting the voltage difference between input and output. The results are presented intuitively to the user via the display module 50, enabling self-testing of the charging connection harness. This ensures a comprehensive high-performance charging experience, from enhanced safety and optimized charging efficiency to prevention of overheating and fire accidents, achieving fast and stable safe charging.

[0095] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A device utilizing a charger self-test data cable, characterized in that, include: The system includes a power supply unit, a power conversion unit, a bidirectional conversion unit, a first interface, and a second interface; the power supply unit is connected to the power conversion unit; the power conversion unit is connected to the first interface; the power supply unit is connected to the bidirectional conversion unit; the bidirectional conversion unit is connected to the second interface; both ends of a data cable are connected to the first interface and the second interface, respectively; the power conversion unit is connected to the bidirectional conversion unit.

2. The device using a charger self-test data cable according to claim 1, characterized in that, The power supply unit includes an AD-DC charger.

3. The device using a charger self-test data cable according to claim 1, characterized in that, The power conversion unit includes a first BUCK chip with a fast charging protocol integrated within it.

4. The device using a charger self-test data cable according to claim 3, characterized in that, The bidirectional conversion unit includes a second BUCK chip with integrated PD bidirectional protocol and a switching element. The second BUCK chip is connected to the switching element, the first BUCK chip, and the second interface, respectively. The switching element is connected to the first BUCK chip and the second interface, respectively.

5. The device using a charger self-test data cable according to claim 1, characterized in that, The first interface includes a TYPE-C interface.

6. The device using a charger self-test data cable according to claim 1, characterized in that, The second interface includes a TYPE-C interface.

7. The device using a charger self-test data cable according to claim 1, characterized in that, Also includes: The control unit and the display module are respectively connected to the power conversion unit and the display module.

8. The device using a charger self-test data cable according to claim 4, characterized in that, The switching device includes a MOSFET.

9. The device using a charger self-test data cable according to claim 7, characterized in that, The display module includes a display screen.

10. The device using a charger self-test data cable according to claim 3, characterized in that, The first BUCK chip is connected to the first interface via a resistor.

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