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Type-C testing process
- 2021-01-05-

Type-C testing process

Type-CThrough CC detection, the configuration steps between DFP and UFP are as follows: detect effective connection → establish power supply mode → configure alternate mode.During the connection process, first determine whether the connection is established by CC1 or CC2 to determine the direction of the positive and negative insertion, and use the USB-PDBMC code signal communication to control the internal switch of the device to normally configure the data transmission and signal correspondence to realize the load The function configuration. When one of the CC lines is used as the Type-C interface configuration signal, the other signal is used as the power supply for the cable E-Marker chip.

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Type-C detection principle:The two CC wires CC1 and CC2, most USB wires (cables without chips) have only one CC wire DFPIt can be judged whether the device has been inserted according to the voltage on the two CC wires. Judge the direction by judging which CC line has a pull-down resistor.If the CC1 pin detects a valid Rp/Rd connection (corresponding voltage), it is considered that the cable connection has not been reversed.If the CC2 pin detects a valid Rp/Rd connection (corresponding voltage), it is considered that the cable connection has been reversed.Note that SSTX/RX channels are exchanged during work, while D+/D-does not need to be exchanged because it is a low-speed signal.

The connection diagram of the CC line is as follows:

连接示意图.jpg

Note: The Pull-up terminal in the figure above can be replaced by a current source.

There are three resistors Rp, Rd, Ra in the above figure. The connection of these three different resistors on the CC line can be used to determine whether it is DFP, UFP, Power, Debug or Audio auxiliary equipment and the connection direction.

From DFP's perspective, the following table lists all possible connection states:

连接状态表.jpg