Serial port communication circuit and electronic equipment

Abstract

The utility model relates to a serial port communication circuit and electronic equipment. The circuit comprises a first controller, a second controller, a first switch unit, a second switch unit, a third switch unit and a fourth switch unit, the first end of the first switch unit is connected with the signal input end of the first controller, the second end of the first switch unit is connected with the first end of the third switch unit, and the second end of the third switch unit is connected with the signal output end of the second controller; the first end of the second switch unit is connected with the signal output end of the first controller, the second end of the second switch unit is connected with the first end of the fourth switch unit, and the second end of the fourth switch unit is connected with the signal input end of the second controller; the control end of the first switch unit and the control end of the second switch unit are connected with the control level output end of the first controller; the control end of the third switch unit and the control end of the fourth switch unit are connected with the control level output end of the second controller. Through the circuit, voltage backward flowing of the communication circuit can be avoided, and the reliability of the whole circuit is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of communication circuits, and more specifically, to a serial port communication circuit and electronic equipment. Background Art

[0002] In actual serial communication circuits, when a device begins operation, the startup processes of two or more MCU circuits involved in communication may vary in time, and simultaneous startup is often not guaranteed. If one MCU circuit starts operating before the other, the serial port voltage of the first MCU circuit will flow through the IO port of the other MCU circuit, causing voltage backflow and malfunctioning of the entire circuit. Utility Model Content

[0003] The technical problem to be solved by the present invention is to provide a serial communication circuit and electronic equipment in view of the above-mentioned defect of the prior art that there is a risk of voltage backflow.

[0004] The technical solution adopted by the utility model to solve the technical problem is: constructing a serial communication circuit, including: a first controller, a second controller, a first switch unit, a second switch unit, a third switch unit and a fourth switch unit;

[0005] A first end of the first switch unit is connected to a signal input end of the first controller, a second end of the first switch unit is connected to a first end of the third switch unit, and a second end of the third switch unit is connected to a signal output end of the second controller;

[0006] A first end of the second switch unit is connected to a signal output end of the first controller, a second end of the second switch unit is connected to a first end of the fourth switch unit, and a second end of the fourth switch unit is connected to a signal input end of the second controller;

[0007] The control end of the first switch unit and the control end of the second switch unit are connected to the control level output end of the first controller;

[0008] The control end of the third switch unit and the control end of the fourth switch unit are connected to the control level output end of the second controller.

[0009] Preferably, in the serial communication circuit described in the present utility model,

[0010] The first switch unit includes a first MOS transistor and a first resistor; the source of the first MOS transistor is connected to the first end of the first resistor and constitutes the first end of the first switch unit, the gate of the first MOS transistor is connected to the second end of the first resistor and constitutes the control end of the first switch unit, and the drain of the first MOS transistor constitutes the second end of the first switch unit; and / or

[0011] The second switch unit includes a second MOS transistor and a second resistor; the source of the second MOS transistor is connected to the first end of the second resistor and constitutes the first end of the second switch unit, the gate of the second MOS transistor is connected to the second end of the second resistor and constitutes the control end of the second switch unit, and the drain of the second MOS transistor constitutes the second end of the second switch unit.

[0012] Preferably, in the serial communication circuit described in the present utility model,

[0013] The third switch unit includes a third MOS transistor and a third resistor; the drain of the third MOS transistor constitutes the first end of the third switch unit, the source of the third MOS transistor is connected to the first end of the third resistor and constitutes the second end of the third switch unit, and the gate of the third MOS transistor is connected to the second end of the third resistor and constitutes the control end of the third switch unit; and / or

[0014] The fourth switch unit includes a fourth MOS transistor and a fourth resistor; the drain of the fourth MOS transistor constitutes the first end of the fourth switch unit, the source of the fourth MOS transistor is connected to the first end of the fourth resistor and constitutes the second end of the fourth switch unit, and the gate of the fourth MOS transistor is connected to the second end of the fourth resistor and constitutes the control end of the fourth switch unit.

[0015] Preferably, in the serial communication circuit of the present utility model, the serial communication circuit further comprises a first driving level generating unit;

[0016] An input end of the first driving level generating unit is connected to a power supply, an output end of the first driving level generating unit is connected to a control end of the first switching unit and a control end of the second switching unit, and a control end of the first driving level generating unit is connected to a control level output end of the first controller.

[0017] Preferably, in the serial communication circuit of the present invention, the first driving level generating unit includes a fifth MOS transistor, a sixth MOS transistor, a fifth resistor, a sixth resistor, a seventh resistor and a first capacitor;

[0018] The source of the fifth MOS transistor is connected to the first end of the fifth resistor and constitutes the input end of the first drive level generating unit, the drain of the fifth MOS transistor is connected to the first end of the first capacitor and constitutes the output end of the first drive level generating unit, and the gate of the fifth MOS transistor is connected to the second end of the fifth resistor and the drain of the sixth MOS transistor;

[0019] The gate of the sixth MOS transistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the seventh resistor and constitutes the control end of the first drive level generating unit, and the source of the sixth MOS transistor, the second end of the seventh resistor, and the second end of the first capacitor are grounded.

[0020] Preferably, in the serial communication circuit of the present utility model, the serial communication circuit further comprises a second driving level generating unit;

[0021] An input end of the second driving level generating unit is connected to a power supply, an output end of the second driving level generating unit is connected to a control end of the third switching unit and a control end of the fourth switching unit, and a control end of the second driving level generating unit is connected to a control level output end of the second controller.

[0022] Preferably, in the serial communication circuit of the present invention, the second driving level generating unit includes a seventh MOS transistor, an eighth MOS transistor, an eighth resistor, a ninth resistor, a tenth resistor and a second capacitor;

[0023] The source of the seventh MOS transistor is connected to the first end of the eighth resistor and constitutes the input end of the second drive level generating unit, the drain of the seventh MOS transistor is connected to the first end of the second capacitor and constitutes the output end of the second drive level generating unit, and the gate of the seventh MOS transistor is connected to the second end of the eighth resistor and the drain of the eighth MOS transistor;

[0024] The gate of the eighth MOS transistor is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to the first end of the tenth resistor and constitutes the control end of the second drive level generating unit, and the source of the eighth MOS transistor, the second end of the tenth resistor, and the second end of the second capacitor are grounded.

[0025] Preferably, in the serial communication circuit of the present invention, the serial communication circuit further includes a power supply circuit;

[0026] The input end of the power supply circuit is used to connect to an external power input, and the output end of the power supply circuit is connected to the power supply end of the first controller and the power supply end of the second controller respectively.

[0027] Preferably, in the serial communication circuit of the present invention, the power supply circuit includes a power connection port and a power conversion circuit;

[0028] The power connection port is used to connect an external power input, and the power conversion circuit is connected to the power connection port and the power supply end of the first controller and the power supply end of the second controller, and is used to convert the external power input and input it to the power supply end of the first controller and the power supply end of the second controller.

[0029] The utility model also provides an electronic device, comprising the serial port communication circuit as described above.

[0030] A serial communication circuit and electronic device implementing the present invention have the following beneficial effects: the communication link can be turned on only when all related MCU circuits start working, thereby avoiding voltage backflow in the communication circuit and improving the reliability of the entire circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0032] Figure 1 This is a logic block diagram of an embodiment of a serial communication circuit of the present utility model;

[0033] Figure 2 This is a partial circuit schematic diagram of an embodiment of a serial communication circuit of the present utility model;

[0034] Figure 3 This is a logic block diagram of another embodiment of a serial communication circuit of the present utility model;

[0035] Figure 4 This is a partial circuit schematic diagram of another embodiment of a serial communication circuit of the present utility model;

[0036] Figure 5 This is a partial circuit principle diagram of another embodiment of a serial communication circuit of the utility model. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described in detail with reference to the accompanying drawings.

[0038] like Figure 1As shown, in a first embodiment of a serial communication circuit of the present invention, the circuit includes: a first controller 110, a second controller 130, a first switch unit 121, a second switch unit 122, a third switch unit 123 and a fourth switch unit 124; a first end of the first switch unit 121 is connected to a signal input end of the first controller 110, a second end of the first switch unit 121 is connected to a first end of the third switch unit 123, and a second end of the third switch unit 123 is connected to a signal output end of the second controller 130; a first end of the second switch unit 122 is connected to a signal output end of the first controller 110, a second end of the second switch unit 122 is connected to a first end of the fourth switch unit 124, and a second end of the fourth switch unit 124 is connected to a signal input end of the second controller 130; a control end of the first switch unit 121 and a control end of the second switch unit 122 are connected to a control level output end of the first controller 110; a control end of the third switch unit 123 and a control end of the fourth switch unit 124 are connected to a control level output end of the second controller 130.

[0039] Specifically, the serial communication circuit of this embodiment implements data transmission between the first controller 110 and the second controller 130. In one embodiment, Figure 2 and Figure 4As shown, the first controller 110 and the second controller 130 may include an MCU chip. For example, the first controller 110 includes an MCU chip MCU1, and the second controller 130 includes an MCU chip MCU2. In other embodiments, the first controller 110 and the second controller 130 may also be other chips that can be obtained by those skilled in the art to implement the functions of the MCU chip. It can be understood that the input and output of the first switch unit 121 and the third switch unit 123 are connected in series. That is, only when the first switch unit 121 and the third switch unit 123 are both in the on state, can the signal receiving end of the first controller 110 receive the communication signal or communication data output by the signal output end of the second controller 130 through the first switch unit 121 and the third switch unit 123. The state of the first switch unit 121 is specifically controlled by the control level outputted by the control level output terminal of the first controller 110. Specifically, the first switch unit 121 is set to an off state by default. After the first controller 110 enters the operating state, or after a series of initialization or confirmation actions, the control level or control voltage is outputted via the control level output terminal. This control level or control voltage is used to control the state of the first switch unit 121 to an on state. Similarly, the state of the third switch unit 123 is specifically controlled by the control level outputted by the control level output terminal of the second controller 130. Specifically, the third switch unit 123 is set to an off state by default. After the second controller 130 enters the operating state, or after a series of initialization or confirmation actions, the control level or control voltage is outputted via the control level output terminal. This control level or control voltage is used to control the state of the third switch unit 123 to an on state. This ensures that the corresponding communication link between the first controller 110 and the second controller 130 is only established when both the first controller 110 and the second controller 130 enter the normal operating state. Based on the same understanding, the inputs and outputs of the second switch unit 122 and the fourth switch unit 124 are connected in series. That is, only when the second switch unit 122 and the fourth switch unit 124 are both in the on state can the communication signal or communication data output from the signal output terminal of the first controller 110 be transmitted through the second switch unit 122 and the fourth switch unit 124 to the signal receiving terminal of the second controller 130. The state of the second switch unit 122 is specifically controlled by the control level output from the control level output terminal of the first controller 110. That is, the second switch unit 122 is set to the off state by default. After the first controller 110 enters the operating state, or after a series of initialization or confirmation actions, the control level or control voltage is output through the control level output terminal, and the state of the second switch unit 122 is controlled to the on state by this control level or control voltage.Similarly, the state of the fourth switch unit 124 is specifically controlled by the control level outputted by the control level output terminal of the second controller 130. That is, the fourth switch unit 124 is set to the off state by default. After the second controller 130 enters the working state, or after a series of initialization or confirmation actions, the control level output terminal may output a control level or a control voltage, and the state of the fourth switch unit 124 may be controlled to the on state by the control level or control voltage. This ensures that the corresponding communication link between the first controller 110 and the second controller 130 is only connected when both the first controller 110 and the second controller 130 enter the normal working state.

[0040] Through the above process, the bidirectional communication link between the first controller 110 and the second controller 130 is ultimately connected only when both the first controller 110 and the second controller 130 enter normal operating conditions. Specifically, the first switch unit 121 and the second switch unit 122 can be controlled by the same control level or control voltage output by the first controller 110, and the third switch unit 123 and the fourth switch unit 124 can be controlled by the same control level or control voltage output by the second controller 130. This process ensures that the bidirectional communication link between the first controller 110 and the second controller 130 is simultaneously connected when both the first controller 110 and the second controller 130 enter normal operating conditions.

[0041] Optional, such as Figure 2 and Figure 4 In the illustrated embodiment, the first switch unit 121 includes a first MOS transistor and a first resistor; the source of the first MOS transistor is connected to the first end of the first resistor and constitutes the first end of the first switch unit 121, the gate of the first MOS transistor is connected to the second end of the first resistor and constitutes the control end of the first switch unit 121, and the drain of the first MOS transistor constitutes the second end of the first switch unit 121. Specifically, the first switch unit 121 can be composed of a MOS transistor and its peripheral circuits. For example, the first switch unit 121 can include a MOS transistor Q1 (corresponding to the first MOS transistor) and a resistor R1 (corresponding to the first resistor). The control level or control voltage of the first controller 110 controls whether the MOS transistor Q1 is turned on or off.

[0042] Optional, such as Figure 2 and Figure 4In the illustrated embodiment, the second switch unit 122 includes a second MOS transistor and a second resistor; the source of the second MOS transistor is connected to the first end of the second resistor and constitutes the first end of the second switch unit 122, the gate of the second MOS transistor is connected to the second end of the second resistor and constitutes the control end of the second switch unit 122, and the drain of the second MOS transistor constitutes the second end of the second switch unit 122. Specifically, the second switch unit 122 can be composed of a MOS transistor and its peripheral circuits. For example, the second switch unit 122 can include a MOS transistor Q2 (corresponding to the second MOS transistor) and a resistor R2 (corresponding to the second resistor). The control level or control voltage of the first controller 110 controls whether the MOS transistor Q2 is turned on or off.

[0043] Optional, such as Figure 2 and Figure 4 In the illustrated embodiment, the third switch unit 123 includes a third MOS transistor and a third resistor. The drain of the third MOS transistor constitutes the first end of the third switch unit 123, the source of the third MOS transistor is connected to the first end of the third resistor and constitutes the second end of the third switch unit 123, and the gate of the third MOS transistor is connected to the second end of the third resistor and constitutes the control end of the third switch unit 123. Specifically, the third switch unit 123 may be composed of a MOS transistor and its peripheral circuits. For example, the third switch unit 123 may include a MOS transistor Q3 (corresponding to the third MOS transistor) and a resistor R3 (corresponding to the third resistor). The control level or control voltage of the second controller 130 controls whether the MOS transistor Q3 is turned on or off.

[0044] Optional, such as Figure 2 and Figure 4 In the illustrated embodiment, the fourth switch unit 124 includes a fourth MOS transistor and a fourth resistor. The drain of the fourth MOS transistor constitutes the first end of the fourth switch unit 124, the source of the fourth MOS transistor is connected to the first end of the fourth resistor and constitutes the second end of the fourth switch unit 124, and the gate of the fourth MOS transistor is connected to the second end of the fourth resistor and constitutes the control end of the fourth switch unit 124. Specifically, the fourth switch unit 124 can be composed of a MOS transistor and its peripheral circuits. For example, the fourth switch unit 124 can include a MOS transistor Q4 (corresponding to the fourth MOS transistor) and a resistor R4 (corresponding to the fourth resistor). The control level or control voltage of the second controller 130 controls whether the MOS transistor Q4 is turned on or off.

[0045] In one embodiment, if Figure 3As shown, the serial communication circuit further includes a first drive level generating unit 141; an input terminal of the first drive level generating unit 141 is connected to a power supply, an output terminal of the first drive level generating unit 141 is connected to a control terminal of the first switch unit 121 and a control terminal of the second switch unit 122, and the control terminal of the first drive level generating unit 141 is connected to a control level output terminal of the first controller 110. Specifically, the control level or control voltage at the control level output terminal of the first controller 110 is used to control the operation of the first drive level generating unit 141 to generate a drive level, which in turn drives the first switch unit 121 and the second switch unit 122 on or off.

[0046] Optional, such as Figure 4 In the illustrated embodiment, the first drive level generating unit 141 includes a fifth MOS transistor, a sixth MOS transistor, a fifth resistor, a sixth resistor, a seventh resistor, and a first capacitor. The source of the fifth MOS transistor is connected to the first end of the fifth resistor and constitutes the input end of the first drive level generating unit 141. The drain of the fifth MOS transistor is connected to the first end of the first capacitor and constitutes the output end of the first drive level generating unit 141. The gate of the fifth MOS transistor is connected to the second end of the fifth resistor and the drain of the sixth MOS transistor. The gate of the sixth MOS transistor is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the first end of the seventh resistor and constitutes the control end of the first drive level generating unit 141. The source of the sixth MOS transistor, the second end of the seventh resistor, and the second end of the first capacitor are grounded. Specifically, the first drive level generating unit 141 can be composed of MOS transistors and their corresponding peripheral circuits. In one specific embodiment, the first drive level generating unit 141 includes a MOS transistor Q5 (corresponding to the fifth MOS transistor), a MOS transistor Q6 (corresponding to the sixth MOS transistor), a resistor R20 (corresponding to the fifth resistor), a resistor R22 (corresponding to the sixth resistor), a resistor R21 (corresponding to the seventh resistor), and a capacitor C19 (corresponding to the first capacitor). The voltage level output from the control level output terminal of the first controller 110 is used to control the on / off state of the MOS transistor Q6 via the resistor R22. This in turn controls the on / off state of the MOS transistor Q5 based on the state of the MOS transistor Q6. When the MOS transistor Q5 is on, the output terminal of the first drive level generating unit 141 outputs a drive level based on the input voltage at the input terminal of the first drive level generating unit 141 to drive the first switch unit 121 and the second switch unit 122 to operate.

[0047] In one embodiment, if Figure 3As shown, the serial communication circuit further includes a second drive level generating unit 142; an input terminal of the second drive level generating unit 142 is connected to a power supply, an output terminal of the second drive level generating unit 142 is connected to a control terminal of the third switch unit 123 and a control terminal of the fourth switch unit 124, and the control terminal of the second drive level generating unit 142 is connected to a control level output terminal of the second controller 130. Specifically, the control level or control voltage at the control level output terminal of the second controller 130 is used to control the operation of the second drive level generating unit 142 to generate a drive level, which in turn drives the third switch unit 123 and the fourth switch unit 124 to turn on or off.

[0048] Optional, such as Figure 4 In the illustrated embodiment, the second drive level generating unit 142 includes a seventh MOS transistor, an eighth MOS transistor, an eighth resistor, a ninth resistor, a tenth resistor, and a second capacitor. The source of the seventh MOS transistor is connected to the first end of the eighth resistor and constitutes the input end of the second drive level generating unit 142. The drain of the seventh MOS transistor is connected to the first end of the second capacitor and constitutes the output end of the second drive level generating unit 142. The gate of the seventh MOS transistor is connected to the second end of the eighth resistor and the drain of the eighth MOS transistor. The gate of the eighth MOS transistor is connected to the first end of the ninth resistor, and the second end of the ninth resistor is connected to the first end of the tenth resistor and constitutes the control end of the second drive level generating unit 142. The source of the eighth MOS transistor, the second end of the tenth resistor, and the second end of the second capacitor are grounded. In a specific embodiment, the second drive level generating unit 142 includes a MOS transistor Q7 (corresponding to the seventh MOS transistor), a MOS transistor Q8 (corresponding to the eighth MOS transistor), a resistor R23 (corresponding to the eighth resistor), a resistor R25 (corresponding to the ninth resistor), a resistor R24 (corresponding to the tenth resistor), and a capacitor C18 (corresponding to the second capacitor). The voltage level outputted by the control level output terminal of the second controller 130 is passed through resistor R25 to control the on / off state of MOS transistor Q8. Consequently, MOS transistor Q7 is turned on or off according to the state of MOS transistor Q8. When MOS transistor Q7 is turned on, the output terminal of the second drive level generating unit 142 outputs a drive level based on the input voltage at the input terminal of the second drive level generating unit 142 to drive the third switch unit 123 and the fourth switch unit 124 to operate.

[0049] Optionally, the serial communication circuit further includes a power supply circuit; the input end of the power supply circuit is used to connect to an external power input, and the output end of the power supply circuit is connected to the power supply end of the first controller 110 and the power supply end of the second controller 130 respectively. Figure 5As shown, in the serial communication circuit, the first controller 110 and the second controller 130 can also be powered by a power supply circuit capable of connecting to an external power input. In another embodiment, the power input to the input terminals of the first drive level generating unit 141 and the second drive level generating unit 142 can both be provided by the power supply circuit. For example, the power supply circuit can introduce an external power input, and the external power input can be used to directly or indirectly power the input terminals of the first drive level generating unit 141 and the second drive level generating unit 142.

[0050] Optionally, the power supply circuit includes a power connection port and a power conversion circuit. The power connection port is used to connect to an external power input. The power conversion circuit is connected to the power connection port and the power supply terminals of the first controller 110 and the second controller 130, and is used to convert the external power input and input it to the power supply terminals of the first controller 110 and the second controller 130. Specifically, in the power supply circuit, the power connection port may include a connector J1, and the power conversion circuit may include a power conversion circuit consisting of a power conversion chip U3 and its peripheral circuits. The external power input is input to the power conversion chip U3 via connector J1, and the power conversion chip U3 performs power conversion to obtain the supply voltage required by the first controller 110 and the second controller 130. Furthermore, the external power input can be connected to a 5V external input through the first pin of connector J1, and this 5V external input is used to power the input terminals of the first drive level generation unit 141 and the second drive level generation unit 142. The peripheral circuits of the power conversion chip U3 are determined by the model of the power conversion chip U3. That is, different power conversion chips U3 may have different corresponding peripheral circuits. By adjusting the peripheral circuits, the output voltage of the power conversion chip U3 can meet the power supply requirements of the first controller 110 and the second controller 130 .

[0051] In addition, an electronic device according to an embodiment of the present invention includes the above serial communication circuit, which is provided in the electronic device to implement signal transmission within the electronic device or between different modules of the electronic device.

[0052] It can be understood that the above embodiments only express the preferred implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A serial communication circuit, characterized in that: include: a first controller, a second controller, a first switch unit, a second switch unit, a third switch unit, and a fourth switch unit; A first end of the first switch unit is connected to a signal input end of the first controller, a second end of the first switch unit is connected to a first end of the third switch unit, and a second end of the third switch unit is connected to a signal output end of the second controller; A first end of the second switch unit is connected to a signal output end of the first controller, a second end of the second switch unit is connected to a first end of the fourth switch unit, and a second end of the fourth switch unit is connected to a signal input end of the second controller; The control end of the first switch unit and the control end of the second switch unit are connected to the control level output end of the first controller; The control end of the third switch unit and the control end of the fourth switch unit are connected to the control level output end of the second controller.

2. The serial communication circuit according to claim 1, wherein: The first switch unit includes a first MOS transistor and a first resistor; the source of the first MOS transistor is connected to the first end of the first resistor and constitutes the first end of the first switch unit, the gate of the first MOS transistor is connected to the second end of the first resistor and constitutes the control end of the first switch unit, and the drain of the first MOS transistor constitutes the second end of the first switch unit; and / or The second switch unit includes a second MOS transistor and a second resistor; the source of the second MOS transistor is connected to the first end of the second resistor and constitutes the first end of the second switch unit, the gate of the second MOS transistor is connected to the second end of the second resistor and constitutes the control end of the second switch unit, and the drain of the second MOS transistor constitutes the second end of the second switch unit.

3. The serial communication circuit according to claim 1, wherein: The third switch unit includes a third MOS transistor and a third resistor; the drain of the third MOS transistor constitutes the first end of the third switch unit, the source of the third MOS transistor is connected to the first end of the third resistor and constitutes the second end of the third switch unit, and the gate of the third MOS transistor is connected to the second end of the third resistor and constitutes the control end of the third switch unit; and / or The fourth switch unit includes a fourth MOS transistor and a fourth resistor; the drain of the fourth MOS transistor constitutes the first end of the fourth switch unit, the source of the fourth MOS transistor is connected to the first end of the fourth resistor and constitutes the second end of the fourth switch unit, and the gate of the fourth MOS transistor is connected to the second end of the fourth resistor and constitutes the control end of the fourth switch unit.

4. The serial communication circuit according to claim 1, wherein: The serial communication circuit further includes a first driving level generating unit; An input end of the first driving level generating unit is connected to a power supply, an output end of the first driving level generating unit is connected to a control end of the first switching unit and a control end of the second switching unit, and a control end of the first driving level generating unit is connected to a control level output end of the first controller.

5. The serial communication circuit according to claim 4, wherein: The first driving level generating unit includes a fifth MOS transistor, a sixth MOS transistor, a fifth resistor, a sixth resistor, a seventh resistor and a first capacitor; The source of the fifth MOS transistor is connected to the first end of the fifth resistor and constitutes the input end of the first drive level generating unit, the drain of the fifth MOS transistor is connected to the first end of the first capacitor and constitutes the output end of the first drive level generating unit, and the gate of the fifth MOS transistor is connected to the second end of the fifth resistor and the drain of the sixth MOS transistor; The gate of the sixth MOS transistor is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the seventh resistor and constitutes the control end of the first drive level generating unit, and the source of the sixth MOS transistor, the second end of the seventh resistor, and the second end of the first capacitor are grounded.

6. The serial communication circuit according to claim 1, wherein: The serial communication circuit further includes a second driving level generating unit; An input end of the second driving level generating unit is connected to a power supply, an output end of the second driving level generating unit is connected to a control end of the third switching unit and a control end of the fourth switching unit, and a control end of the second driving level generating unit is connected to a control level output end of the second controller.

7. The serial communication circuit according to claim 6, wherein: The second driving level generating unit includes a seventh MOS transistor, an eighth MOS transistor, an eighth resistor, a ninth resistor, a tenth resistor and a second capacitor; The source of the seventh MOS transistor is connected to the first end of the eighth resistor and constitutes the input end of the second drive level generating unit, the drain of the seventh MOS transistor is connected to the first end of the second capacitor and constitutes the output end of the second drive level generating unit, and the gate of the seventh MOS transistor is connected to the second end of the eighth resistor and the drain of the eighth MOS transistor; The gate of the eighth MOS transistor is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to the first end of the tenth resistor and constitutes the control end of the second drive level generating unit, and the source of the eighth MOS transistor, the second end of the tenth resistor, and the second end of the second capacitor are grounded.

8. The serial communication circuit according to claim 1, wherein: The serial communication circuit also includes a power supply circuit; The input end of the power supply circuit is used to connect to an external power input, and the output end of the power supply circuit is connected to the power supply end of the first controller and the power supply end of the second controller respectively.

9. The serial communication circuit according to claim 8, wherein: The power supply circuit includes a power connection port and a power conversion circuit; The power connection port is used to connect an external power input, and the power conversion circuit is connected to the power connection port and the power supply end of the first controller and the power supply end of the second controller, and is used to convert the external power input and input it to the power supply end of the first controller and the power supply end of the second controller.

10. An electronic device, characterized in that: The serial communication circuit comprises the serial communication circuit according to any one of claims 1 to 9.

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