By PURPLELEC | 14 March 2024 | 0 Comments
Identification of roles of both sides of USB-C/TYPE-C interface
The identification of roles on both sides of the TYPE-C interface is actually detected and set through the two CC lines in the TYPE-C interface. As shown below:
The cable device here means that the cable with the eMark chip will use Vconn for power supply. When one CC confirms the direction, the other CC at the Source end will switch to Vconn to power the Emark. The cable with the Emark chip can communicate with the device through the CC Communicating and feeding back the cable's temperature and current-carrying energy information is of great help to the safety of high-power charging.
1. Interface 1 serves as the power supply, and a pull-up resistor (Rp) is added to the two CC lines of the interface;
2. Interface 2 is a power consumer, and a pull-down resistor (Rd) is added to the two CC lines of the interface.
3. When two interfaces are connected and interface 1 recognizes the other party's Rd pull-down, it is considered that the connection is successful and the other party's role is detected as a power consumer;
4. When interface 2 recognizes the other party's Rp pull-up, it is considered that the connection is successful and the other party's role is detected as the power supply party. If two interfaces that are both power suppliers or power consumers are connected, then neither party can recognize the desired Rd pull-down or Rp pull-up, and neither party can work.
For dual role (DRP) interfaces, the two CCs will continuously switch between the Rp pull-up state and the Rd pull-down state.
When connected to a non-dual role device, if the other party is Rp pull-up, the interface will stop in the Rd pull-down state. At this time, the power supply role of the interface is the power consumer:
If the other party is Rd pull-down, the interface will stop in the Rp pull-up state. At this time, the power supply role of the interface is the power supply side. When connected to a dual-role device, both parties will randomly stop in the Rp pull-up state or Rd pull-down state. When The connection is established when one party stops in the Rp pull-up state and the other party stops in the Rd pull-down state. The side that stops in the pull-up state of Rp is the power supply side, and the side that stops in the pull-down state of Rd is the power consumer.
Regardless of whether it is a power supply role or a communication function role, the initial role determined when connecting is not always unchanged. It can be switched through the power supply protocol. The specific details will be introduced later. A product is designed as a pure power supply party and its communication function is UFP. Because the product's power supply role can only be a power supply party when connected, the communication function is DFP when connected. After connection, the product needs to switch the communication function to UFP through the power supply protocol.
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