CN204576500U - A kind of usb communication circuit of compatible I2C communication and system - Google Patents

Abstract

The utility model discloses a USB communication circuit and system compatible with I2C communication. The circuit comprises: a USB interface, wherein the USB interface includes a USB interface plug and a USB interface main board; the first identification pin of the USB interface plug and the first resistance pin The first end is connected, and also connected with the slave serial clock end of the slave device; the first ground pin of the USB interface plug is connected with the first end of the second resistor, and also connected with the slave serial data end of the slave device ; The second end of the first resistor and the second end of the second resistor are grounded; the second identification pin of the USB interface motherboard is connected with the general input/output end of the host device, and also connected with the main serial clock of the I2C interface of the host device The second ground pin of the USB interface motherboard is connected with the general input/output terminal of the host device, and is also connected with the main serial data terminal of the I2C interface of the host device. The utility model is simultaneously compatible with USB communication and I2C communication.

Description

A USB communication circuit and system compatible with I2C communication

technical field

The utility model relates to the communication field, in particular to a USB communication circuit and system compatible with I2C communication.

Background technique

Universal Serial Bus (Universal Serial Bus, USB) is an external bus standard used to standardize the connection and communication between computers and external devices. Plug-and-play and hot-swappable functions for external devices.

Referring to Fig. 1 (a), it is a schematic diagram of a USB interface mainboard side provided by the prior art, as shown in the figure, the identification (Identity, ID) pin of the USB interface mainboard side is directly connected to a central processing unit (Central Processing Unit, CPU ) general purpose input/output (General Purpose Input Output, GPIO) connection, used for data exchange between external devices and the host where the CPU is located (On-The-Go, OTG identification), its ground pin (GND-3) directly Ground, other ground pins (GND-1, GND-5, GND-6, GND-7, GND-2, GND-4) are directly grounded. Here, the USB interface motherboard also includes a positive voltage data terminal (DataPositive, D+), a negative voltage data terminal (Data Negative, D-), and a power supply terminal VUSB. Among them, the D+ terminal is connected to a wire to transmit high-speed positive data to the host. For voltage data (High Speed Data Positive, HS_DP), the D-terminal is connected to a wire to transmit high-speed negative voltage data (High Speed Data Negative, HS_DN) with the host, and the power supply terminal VUSB is connected to the power supply USB_VCHR. Referring to Figure 1(b), a schematic diagram of a USB interface connector provided in the prior art, as shown in the figure, the identification pin (ID) and the ground pin (GND-3) of the USB interface connector are grounded respectively . It can be seen that the existing USB interface can only be used for USB communication, charging and OTG identification, and its function is single. Here, the USB interface connector also includes a positive voltage data terminal (Data Positive, D+), a negative voltage data terminal (Data Negative, D-), and a power supply terminal VUSB. Among them, the D+ terminal is connected to a line for transmission with the slave. High-speed positive voltage data (High SpeedData Positive, HS_DP), D-terminal is connected to a line, and high-speed negative voltage data (High Speed Data Negative, HS_DN) is transmitted between the slave, and the power supply terminal VUSB is connected to the power supply USB_VCHR.

The built-in integrated circuit (Inter-Integrated Circuit, I2C) bus is a two-wire serial bus, which is used to connect the host and its peripherals, and facilitates the communication between the host and peripherals. It is a bus standard widely used in the field of microelectronics communication control .

The existing I2C interface realizes the reliable communication between the host computer and the peripheral equipment through the I2C bus, or realizes the reliable communication between the host computer and the peripheral equipment through the USB to I2C adapter, and the cost is high and the wiring is complicated.

Utility model content

The utility model provides a USB communication circuit and system compatible with I2C communication to increase the function of the USB interface and reduce the cost of I2C bus communication.

In the first aspect, the utility model provides a USB communication circuit compatible with I2C communication, comprising: a USB interface, wherein the USB interface includes a USB interface plug and a USB interface main board;

The first identification pin of the USB interface plug is connected with the first end of the first resistor, and is also connected with the slave serial clock end of the slave device; the first ground pin of the USB interface plug is connected with the second resistor connected to the first end of the slave device, and also connected to the slave serial data end of the slave device; the second end of the first resistor and the second end of the second resistor are grounded;

The second identification pin of the USB interface main board is connected with the universal input/output end of the host device, and is also connected with the main serial clock end of the I2C interface of the host device; the second ground lead of the USB interface main board The pin is connected with the general-purpose input/output end of the host device, and is also connected with the main serial data end of the I2C interface of the host device.

Further, the wiring connected to the general-purpose input/output terminal of the second identification pin is shared with the wiring connected to the main serial clock terminal.

Further, the wiring of the second ground pin connected to the general-purpose input/output terminal is shared with the wiring connected to the main serial data terminal.

Further, the shell of the USB interface is grounded.

In the second aspect, the utility model provides a USB communication system compatible with I2C communication, comprising: the USB communication circuit as described in the first aspect, a host device and a slave device;

The host device is connected to the USB interface main board, and the slave device is connected to the USB interface plug.

Further, the host device at least includes an I2C interface and a general-purpose input/output terminal;

The general-purpose input/output terminal is connected to the second identification pin of the USB interface motherboard, and is also connected to the second ground pin of the USB interface motherboard;

The main serial clock terminal of the I2C interface is connected to the second identification pin, and the main serial data terminal of the I2C interface is connected to the second ground pin.

Further, the slave device includes at least a slave serial clock terminal and a slave serial data terminal;

The slave serial clock terminal is connected to the first identification pin of the USB interface plug; the slave serial data terminal is connected to the first ground pin of the USB interface plug.

Further, the slave device has an I2C interface; or, the slave device has a USB interface.

The utility model provides a USB communication circuit and system compatible with I2C communication. The first identification pin of the USB interface plug is respectively connected with the first end of the first resistor and the slave serial clock end of the slave device. The ground wire pins are respectively connected to the first end of the second resistor and the slave serial data end of the slave device, and the second end of the first resistor and the second end of the second resistor are grounded, so as to realize the connection with I2C through the USB interface. Access identification of the slave device of the interface. The second identification pin of the USB interface motherboard is respectively connected to the general input/output end of the host device and the main serial clock end of the I2C interface of the host device, and the second ground pin is respectively connected to the general input/output end of the host device, the host The main serial data end of the device I2C interface is connected to realize the I2C bus communication between the slave device with the I2C interface and the host device through the USB interface. The utility model is compatible with USB communication and I2C communication at the same time, increases the function of the USB interface, and reduces the cost of I2C bus communication.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description The drawings show some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creative work.

Fig. 1 (a) is the schematic diagram of a kind of USB interface motherboard end that prior art provides;

Fig. 1 (b) is the schematic diagram of a kind of USB interface joint end provided by prior art;

Fig. 2 (a) is a schematic diagram of a USB interface plug of a USB communication circuit compatible with I2C communication provided by Embodiment 1 of the present invention;

Fig. 2 (b) is a schematic diagram of a USB interface motherboard of a USB communication circuit compatible with I2C communication provided by Embodiment 1 of the present invention;

Fig. 3 (a) is a schematic diagram of a USB communication system compatible with I2C communication provided by Embodiment 2 of the present invention;

Fig. 3(b) is a flow chart of a USB communication method compatible with I2C communication provided by Embodiment 2 of the present invention.

detailed description

In order to make the purpose, technical solutions and advantages of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described through implementation modes with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments It is a part of embodiments of the present utility model, but not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Embodiment one

The technical solution of the first embodiment is applicable to the case of multiplexing the USB interface as the I2C interface for I2C communication and USB communication.

The utility model provides a USB communication circuit compatible with I2C communication, comprising: a USB interface, wherein the USB interface includes a USB interface plug and a USB interface main board.

Referring to FIG. 2( a ), it is a schematic diagram of a USB interface plug of a USB communication circuit compatible with I2C communication provided by Embodiment 1 of the present invention. Wherein, the USB interface plug in this embodiment is used for the host device to detect whether there is a slave device with an I2C interface connected to the USB communication circuit. If there is no slave device with an I2C interface connected to the USB communication circuit, the USB communication circuit is only used as a traditional USB interface for the slave device and the host device to perform USB communication, charging, OTG identification, etc. through the USB interface. If a slave device with an I2C interface is connected to the USB communication circuit, the USB communication circuit can be reused as an I2C interface for I2C communication between the slave device and the host device through the I2C interface.

The first identification pin ID of the USB interface plug is connected to the first end of the first resistor R1, and also connected to the slave serial clock terminal (Serial Clock, SCL) of the slave device. Specifically, the first identification pin is connected to the first resistor through a wiring, and the first identification pin is also connected to the slave serial clock terminal of the slave device through another wiring SCL/ID, so connecting the slave serial The wiring SCL/ID of the clock terminal and the first identification pin can be used as a clock line for I2C interface communication, and is used to transmit a clock signal between the slave device and the master device.

The first ground pin GND-3 of the USB interface plug is connected to the first end of the second resistor R2, and is also connected to the slave serial data terminal (Serial Data, SDA) of the slave device. Specifically, the first ground pin is connected to the second resistor through a wiring, and the first ground pin is also connected to the slave serial data terminal of the slave device through another wiring SDA/ID, so the connection of the slave The wiring SDA/ID of the serial data terminal and the first ground pin can be used as a data line for I2C interface communication, and is used to transmit data signals between the slave device and the master device.

The second end of the first resistor and the second end of the second resistor are also directly grounded. Here, large resistors are selected as the first resistor and the second resistor. When the second terminal of the first resistor and the second terminal of the second resistor are directly grounded, the first resistor and the second resistor are used as pull-down resistors in the In the USB communication circuit, the first end of the first resistor will pull down the voltage of the first identification pin of the USB interface plug, and clamp the voltage of the first identification pin to a lower voltage value. Similarly, the second The first end of the resistor will pull down the voltage on the first ground pin, clamping its voltage at a lower voltage value. In this way, the USB interface plug is used for access identification of the slave device with the I2C interface. Optionally, the resistance value of the first resistor is equal to the resistance value of the second resistor, the resistance value of the first resistor is 200KΩ, and the resistance value of the second resistor is 200KΩ.

As mentioned above, the USB interface plug is connected with a large resistor to pull down the pin voltage. Therefore, when the USB communication circuit communicates as an I2C interface, the communication method of the USB communication circuit can only use the push-pull communication (Push Pull) method.

As mentioned above, the USB interface plug can identify the slave device with the I2C interface, so the slave device connected to the plug part of the USB interface can be a slave device with a USB interface or a slave device with an I2C interface. machine parts.

It is known that the first identification pin and the first ground pin of the USB interface plug are respectively connected to the SCL/ID wiring and the SDA/ID wiring. Here, the USB interface plug also includes other pins, specifically positive voltage data Terminal D+, negative voltage data terminal D-, power supply terminal VUSB, ground terminal (GND-1, GND-5, GND-6, GND-7, GND-2, GND-4), where D+ is connected to a wire, HS_DP is transmitted between the slave device, D- is connected to a trace, HS_DN is transmitted between the slave device, VUSB is connected to the power supply USB_VCHR, and the ground terminal is grounded respectively.

After the pull-down resistor is connected to the USB interface plug of the USB communication circuit, in order to make the USB communication circuit have a function compatible with I2C interface communication, the connection relationship of the interface motherboard part of the USB communication circuit is also changed.

Referring to FIG. 2( b ), it is a schematic diagram of a USB interface motherboard of a USB communication circuit compatible with I2C communication provided by Embodiment 1 of the present invention. Wherein, the USB interface motherboard in this embodiment is used for the host device to identify the access of the connected slave device. When the host device recognizes that the connected slave device is a slave device with an I2C interface, the host device passes The USB interface performs I2C communication with a slave device with an I2C interface. When the host device recognizes that the connected slave device is a slave device without an I2C interface, the host device performs USB communication with the slave device through the USB interface. Then the USB communication circuit is compatible with the I2C interface and the USB interface.

The second identification pin ID of the USB interface motherboard is connected to the general input/output terminal GPIO of the host device, and also connected to the main serial clock terminal SCL of the I2C interface of the host device. Specifically, the second identification pin is connected to a routing, and the routing GPIO1 is connected to the general-purpose input/output terminal of the host device as an input/output line, and the routing is used as the access of the host device to the slave device The transmission of the identification signal; the second identification pin is also connected to a line, and the line SCL/ID is connected to the main serial clock terminal of the I2C interface of the host device as a clock line, and the line is used as a slave device Transmission of clock signals to and from the host device.

The second ground pin GND-3 of the USB interface motherboard is connected to the general input/output terminal GPIO of the host device, and is also connected to the main serial data terminal SDA of the I2C interface of the host device. Specifically, the second ground pin is connected to a wiring, and the wiring GPIO2 is connected to the general-purpose input/output terminal of the host device as an input/output line, and the wiring is used as a connection between the host device and the slave device. The transmission of the input identification signal; the second ground pin is also connected with a trace, and the trace SDA/ID is connected to the main serial data terminal of the I2C interface of the host device as a data line, and the trace is used as a slave The transmission of data signals between the machine device and the host device.

As mentioned above, due to the wiring used for access identification signal transmission connected to the general-purpose input/output terminal of the host device, and the wiring used for clock signal transmission connected to the main serial clock terminal of the I2C interface of the host device , are all connected to the second identification pin of the USB interface motherboard. Therefore, optionally, the wiring that the second identification pin is connected to the general-purpose input/output terminal can share with the wiring that is connected to the main serial clock terminal, and both use the SCL/ID wiring to transmit signals.

As mentioned above, due to the wiring used for access identification signal transmission connected to the general-purpose input/output terminal of the host device, and the wiring used for data signal transmission connected to the main serial data terminal of the I2C interface of the host device , are connected to the second ground pin of the USB interface motherboard. Therefore, optionally, the wiring that the second ground pin is connected to the general-purpose input/output terminal can share with the wiring that is connected to the main serial data terminal, and both use the SDA/ID wiring to transmit signals.

It is known that the second identification pin and the second ground pin of the USB interface motherboard are respectively connected to the SCL/ID wiring and the SDA/ID wiring. Here, the USB interface plug also includes other pins, specifically positive voltage data Terminal D+, negative voltage data terminal D-, power supply terminal VUSB, ground terminal (GND-1, GND-5, GND-6, GND-7, GND-2, GND-4), where D+ is connected to a wire, HS_DP is transmitted with the host device, D- is connected to a trace, HS_DN is transmitted with the host device, VUSB is connected to the power supply USB_VCHR, and the ground terminals are grounded respectively.

As mentioned above, in this embodiment, the first identification pin and the first ground pin of the interface plug part of the USB interface are not grounded, but are connected with a pull-down resistor and a wiring for communicating with the slave device, and The second identification pin and the second ground pin of the interface motherboard part of the USB interface are not grounded, but are connected with the wiring for communication and transmission with the host device, so the USB interface is not grounded as a whole. Here, the USB The shell of the interface is grounded instead of the direct grounding of the traditional USB interface ground pin.

The above describes the structure of a USB communication circuit compatible with I2C communication. Here, when a slave device with an I2C interface or a USB interface is connected to the USB communication circuit, the transmission process of the USB communication circuit is as follows.

The slave device is connected to the plug part of the USB interface, and the host device is connected to the motherboard part of the USB interface. The general-purpose input/output terminal of the host device is connected to the identification pin and the ground pin of the USB interface motherboard, and the host device recognizes the access of the slave device through the general-purpose input/output terminal, and identifies whether the slave device has an I2C interface.

If the host device recognizes that the slave device is a slave device with an I2C interface, the USB communication circuit communicates as an I2C interface, and the slave device is connected to the first identification pin of the plug part of the USB interface. And the host device is connected to the second identification pin of the USB interface main board, and the host device and the slave device perform I2C communication to transmit the clock signal, that is, the slave device transmits the clock to the host device through the identification pin The signal or master device transmits a clock signal to the slave device through the identification pin. The slave device is also connected to the first ground pin of the USB interface plug part, and the host device is also connected to the second ground pin of the USB interface motherboard part, the host device and the slave I2C communication between the components to transmit data signals, that is, the slave device transmits data signals to the master device through the ground pin or the master device transmits data signals to the slave device through the ground pin. All I2C communication between the slave device and the host device is performed through the USB communication circuit.

If it is not recognized that the slave device has an I2C interface, the USB communication circuit is used as a traditional USB interface, and the slave device is connected to the host device through the USB communication circuit, and USB communication, charging and charging are performed between the slave device and the host device. USB communication such as OTG identification.

The utility model provides a USB communication circuit compatible with I2C communication. The first identification pin of the USB interface plug is respectively connected to the first end of the first resistor and the slave serial clock end of the slave device. The first ground wire The pins are respectively connected to the first end of the second resistor and the slave serial data end of the slave device, and the second end of the first resistor and the second end of the second resistor are grounded to realize the I2C interface through the USB interface. Access identification of slave devices. The second identification pin of the USB interface motherboard is respectively connected to the general input/output end of the host device and the main serial clock end of the I2C interface of the host device, and the second ground pin is respectively connected to the general input/output end of the host device, the host The main serial data end of the device I2C interface is connected to realize the I2C bus communication between the slave device with the I2C interface and the host device through the USB interface. The utility model is compatible with USB communication and I2C communication at the same time, increases the function of the USB interface, does not need to transfer the I2C interface adapter through the USB interface, directly uses the USB communication circuit to perform I2C interface communication, and reduces the cost of I2C bus communication.

Embodiment two

Referring to FIG. 3( a ), it is a schematic diagram of a USB communication system compatible with I2C communication provided by Embodiment 2 of the present invention. The technical solution of this embodiment uses the situation that the I2C interface is multiplexed with the USB interface.

The utility model provides a universal serial bus communication system compatible with built-in integrated circuit bus communication, comprising: a USB communication circuit 11 as in Embodiment 1, a host device 12 and a slave device 13; the host device 12 and the USB interface main board 14 To connect, the slave device 13 is connected to the USB interface plug 15.

Optionally, the host device 12 includes at least an I2C interface and a general-purpose input/output terminal GPIO; the general-purpose input/output terminal is connected to the second identification pin of the USB interface motherboard 14, and is also connected to the second ground pin of the USB interface motherboard 14 connection; the main serial clock terminal of the I2C interface is connected to the second identification pin, and the main serial data terminal of the I2C interface is connected to the second ground pin.

Optionally, the slave device 13 at least includes a serial clock terminal and a serial data terminal; the serial clock terminal is connected to the first identification pin of the USB interface plug 15; the serial data terminal is connected to the USB interface plug 15 The first ground pin connection.

Optionally, the slave device 13 has an I2C interface; or, the slave device 13 has a USB interface.

As mentioned above, when the slave device and the host device 12 are respectively connected to the USB communication circuit 11, the host device 12 must first perform access identification on the slave device 13, and only after the access identification can the USB communication circuit 11 follow the USB Interface or I2C interface for communication, the host device 12 controls or uses the external slave device 13 . If the slave device 13 is a slave device 13 with an I2C interface, the USB communication circuit 11 is used as an I2C interface, and if the slave device 13 is a slave device 13 without an I2C interface, the USB communication circuit 11 is used as a USB interface application. Therefore, the principle of the above-mentioned USB communication circuit 11 compatible with I2C communication is as follows:

The ID pin of the known USB interface main board 14 is connected with the GPIO of the host device 12, the GND-3 pin is connected with the GPIO of the host device 12, and the ID pin of the USB interface plug 15 is connected with the slave serial port clock end of the slave device 13 , the GND-3 pin is connected to the slave serial data end of the slave device 13, and the ID pin and the GND-3 pin of the USB interface plug 15 are clamped at a low potential by grounding resistors R1 and R2, so the host device 12 passes through The GPIO and the pull-down resistors R1 and R2 identify the access of the slave device 13 .

Referring to FIG. 3( b ), it is a flowchart of a USB communication method compatible with I2C communication provided by Embodiment 2 of the present invention. The method can be implemented by USB communication compatible with I2C communication, and the system can be implemented in the form of hardware. The method includes the following steps:

Step 21, detecting whether the GPIO is pulled low. The host device 12 will first detect whether the level of the general-purpose input/output terminal connected to the second identification pin of the USB interface motherboard 14 is pulled down. The GPIO uses the internal pull-up of the host device 12 as a USB device access detection for the slave device 13 with the I2C interface.

If host device 12 does not detect that the level of its general-purpose input/output terminal is pulled low, then host device 12 returns and restarts to detect whether the level of the general-purpose input/output terminal connected with the second identification pin of USB interface motherboard 14 is pulled down. pull down. The USB communication circuit 11 serves as a USB interface, and the host device 12 and the slave device 13 perform USB communication, charging or OTG identification through the USB communication circuit 11 .

Step 22, the master device 12 performs I2C communication, and detects whether the slave device 13 responds. If the host device 12 detects that the level of its general-purpose input/output terminal is pulled low, the host device 12 performs I2C communication through the USB communication circuit 11, that is, the host device 12 passes through the ID and the GND-3 pin of the USB interface motherboard 14, and through The ID and GND-2 pins of the USB interface plug 15 communicate with the slave device 13 , that is, initiate a response to the slave device 13 , and detect whether there is a feedback from the slave device 13 .

Step 23, transfer to the OTG process. If the host device 12 initiates a response to the slave device 13, and when no feedback response from the slave device 13 is detected, the USB communication circuit 11 changes over to the OTG identification process, and the host device 12 communicates with the slave device through the USB communication circuit 11. 13 Perform OTG identification.

After the OTG process is completed, the host device 12 returns and restarts to detect whether the level of the general-purpose input/output terminal connected to the second identification pin of the USB interface motherboard 14 is pulled low. The USB communication circuit 11 serves as a USB interface, and the host device 12 and the slave device 13 perform USB communication, charging or OTG identification through the USB communication circuit 11 .

Step 24, perform I2C communication. When the host device 12 detects that there is a response feedback from the slave device 13, the host device 12 confirms that the slave device 13 with the I2C interface is connected to the USB communication circuit 11, and the current USB communication circuit 11 is used as the I2C interface, and the host device 12 passes The I2C interface realizes I2C communication with the slave device 13, and realizes other related functions of I2C communication. Here, the communication between the host device 12 and the slave device 13 is realized through the ID and GND-3 pins of the USB interface motherboard 14 and the ID and GND-3 pins of the USB interface plug 15 . The master device 12 controls the slave device 13 through the I2C interface.

As mentioned above, optionally, the slave device 13 is a slave device 13 with an I2C interface; or, the slave device 13 is a slave device 13 with a USB interface.

Embodiment 2 of the present invention provides a USB communication system compatible with I2C communication. The host device is connected to the USB interface main board, and the slave device is connected to the USB interface plug. The USB communication system can not only be used with an external slave with an I2C interface Machine devices, or cables with USB interfaces with I2C interfaces, can also be compatible with traditional USB interfaces to realize USB communication and I2C communication. The USB communication system can be compatible with OTG identification, USB communication, and can also drive USB with I2C interfaces. The interface is an external slave device or a USB interface cable.

Note that the above are only preferred embodiments of the present invention and the applied technical principles. Those skilled in the art will understand that the utility model is not limited to the specific embodiments described here, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the utility model. Therefore, although the utility model has been described in detail through the above embodiments, the utility model is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the utility model. The scope of the present invention is determined by the appended claims.

Claims (8)

1. A USB communication circuit compatible with I2C communication, characterized in that, comprising: a USB interface, wherein the USB interface comprises a USB interface plug and a USB interface main board; The first identification pin of the USB interface plug is connected with the first end of the first resistor, and is also connected with the slave serial clock end of the slave device; the first ground pin of the USB interface plug is connected with the second resistor connected to the first end of the slave device, and also connected to the slave serial data end of the slave device; the second end of the first resistor and the second end of the second resistor are grounded; The second identification pin of the USB interface main board is connected with the universal input/output end of the host device, and is also connected with the main serial clock end of the I2C interface of the host device; the second ground lead of the USB interface main board The pin is connected with the general-purpose input/output end of the host device, and is also connected with the main serial data end of the I2C interface of the host device. 2. The USB communication circuit compatible with I2C communication according to claim 1, wherein the second identification pin is connected to the wiring of the general-purpose input/output end, and is connected to the wiring of the main serial clock end. Wire sharing. 3. The USB communication circuit compatible with I2C communication according to claim 1, wherein the second ground pin is connected to the wiring of the general-purpose input/output terminal, and is connected to the main serial data line. The wiring at the end is shared. 4. The USB communication circuit compatible with I2C communication according to claim 1, characterized in that the shell of the USB interface is grounded. 5. A USB communication system compatible with I2C communication, characterized in that, comprising: the USB communication circuit according to any one of claims 1-4, a host device and a slave device; The host device is connected to the USB interface main board, and the slave device is connected to the USB interface plug. 6. The USB communication system compatible with I2C communication according to claim 5, wherein the host device at least includes an I2C interface and a general-purpose input/output terminal; The general-purpose input/output terminal is connected to the second identification pin of the USB interface motherboard, and is also connected to the second ground pin of the USB interface motherboard; The main serial clock terminal of the I2C interface is connected to the second identification pin, and the main serial data terminal of the I2C interface is connected to the second ground pin. 7. The USB communication system compatible with I2C communication according to claim 5, wherein the slave device at least includes a slave serial clock terminal and a slave serial data terminal; The slave serial clock terminal is connected to the first identification pin of the USB interface plug; the slave serial data terminal is connected to the first ground pin of the USB interface plug. 8. The USB communication system compatible with I2C communication according to claim 7, wherein the slave device has an I2C interface; or, the slave device has a USB interface.