The hot plug detection of the type-c interface is achieved by detecting the status of CC1 and CC2. As shown in Figure 1, interface 1 is the power supplier, and there is an Rp pull-up on CC1 and CC2 of the interface. Interface 2 is the power consumer, and there is Rd pull-down on CC1 and CC2 of the interface. The CC1 pins at both ends of a normal type-c cable are connected and connected, while CC2 is disconnected (CC2 is used to achieve Vconn power supply function).

The detection principle of hot swapping for type-c interface: When interface 1 and interface 2 are connected through type-c cables, due to the presence of forward and reverse plugging, interface 1 will detect that CC1 or CC2 has a pull-down resistance, indicating that the device has been inserted. Similarly, when interface 2 detects that there is a Pull-up resistor on CC1 or CC2, it is considered that the device is inserted. Subsequently, Interface 1 will switch the state machine. When the states of CC1 and CC2 are stable and meet the requirements for state machine time (please refer to the type-c interface specification document for state machines), Interface 1 will provide 5V to VBus and consider the connection successful. Similarly, after the state machine of interface 2 detects that CC1 and CC2 are stable and Vbus is powered on, it is considered a successful connection. When the connection between type-c interface 1 and interface 2 is disconnected, interface 1 will detect the removal of the pull-down resistance of CC1 or CC2, indicating that the connection is disconnected. Similarly, when interface 2 detects that the Vbus is not powered or the Pull-up resistor of CC1/CC2 is removed, the connection is considered disconnected.

The type-c interface and connector are symmetrical on both sides, and this symmetrical design can support forward and backward insertion, making USB more convenient and efficient in practical use. The detection of forward and backward insertion is also based on two pins, CC1 and CC2. When the devices connected to each other are all interfaces and connected through a type-c cable with connectors at both ends, the situation is more complex, with a total of four types of type-c cable connections. When the type-c cable is inserted into interface 1, the CC1 of the cable is connected to the CC1 of interface 1. If interface 1 can detect a pull-down on CC1, it is considered to be inserted directly; On the contrary, if CC1 of the cable is connected to CC2 of interface 1, so that interface 1 can detect a pull-down on CC2, it is considered a reverse insertion. The same applies to type-c interface 2. If a pull up is detected on CC1, it is considered positive insertion, and if a pull up is detected on CC2, it is considered reverse insertion.

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