Interface circuit, interface circuit protection method, and terminal device

A terminal device, wherein the terminal device comprises an interface circuit;

• wherein the interface circuit comprises a switching unit, a power input end, a first function pin, a second function pin, a control signal input end, a detection port, a grounding output end, a first resistor, a second resistor, a third resistor, a fourth resistor, and an on-off apparatus;
• the switching unit comprises a wire grounding GND end, a circuit power supply Vcc end, a first switch circuit, and a second switch circuit, wherein the first switch circuit comprises a first input end, a second input end, a first control end, and a first output end, and the second switch circuit comprises a third input end, a fourth input end, a second control end, and a second output end;
• the first output end is connected to the first function pin, and the second output end is connected to the second function pin;
• the first resistor is connected in series between the circuit power supply Vcc end and the power input end;
• one end of the second resistor is connected to the wire grounding GND end, and the other end of the second resistor is grounded;
• one end of the third resistor is connected to the control signal input end, and the other end of the third resistor is connected to the first control end and the second control end;
• one end of the fourth resistor is connected to the detection port, and the other end of the fourth resistor is connected to the first input end and the third input end;
• the on-off apparatus comprises an input pin, a first on-off pin, and a second on-off pin;
• the input pin is connected to the power input end;
• the first on-off pin is separately connected to the second input end and the fourth input end;
• the second on-off pin is grounded and connected to the grounding output end;
• when the input pin inputs a low level, the first on-off pin is disconnected from the second on-off pin;
• when the input pin inputs a high level, the first on-off pin is connected from the second on-off pin;
• and
• the switching unit is configured to switch, in response to a control signal that is input through the control signal input end, functions corresponding to the first function pin and the second function pin.