USB-C (formerly known as USB Type-C) is a 24-pin USB connector system with a rotationally symmetrical connector. The USB Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014. It was developed at roughly the same time as the USB 3.1 specification. In July 2016, it was adopted by the IEC as "IEC 62680-1-3". A device with a Type-C connector does not necessarily implement USB, USB Power Delivery, or any Alternate Mode: the Type-C connector is common to several technologies while mandating only a few of them.
USB 3.2, released in September 2017, replaces the USB 3.1 standard. It preserves existing USB 3.1 Super Speed and Super Speed+ data modes and introduces two new Super Speed+ transfer modes over the USB-C connector using two-lane operation, with data rates of 10 and 20 G bit/s (1 and ~2.4 GB/s).
USB4, released in 2019, is the first USB transfer protocol standard that is only available via USB-C.
The 24-pin double-sided connector is slightly larger than the micro-B connector, with a USB-C port measuring 8.4 millimeters (0.33 in) wide, 2.6 millimeters (0.10 in) high, and 6.65 millimeters (0.262 in) deep. Two kinds (genders) of connectors exist, female (receptacle) and male (plug).
Plugs are found on cables and adapters. Receptacles are found on devices and adapters.
USB 3.1 cables are considered full-featured USB-C cables. They are electronically marked cables that contain a chip with an ID function based on the configuration channel and vendor-defined messages (VDM) from the USB Power Delivery 2.0 specification. Cable length should be ≤2 m for Gen 1 or ≤1 m for Gen 2. The electronic ID chip provides information about product/vendor, cable connectors, USB signalling protocol (2.0, Gen 1, Gen 2), passive/active construction, use of V CONN power, available V BUS current, latency, RX/TX directionality, SOP controller mode, and hardware/firmware version. USB-C cables that do not have shielded Super Speed pairs, side band use pins, or additional wires for power lines can have increased cable length, up to 4 m. These USB-C cables only support 2.0 speeds and do not support alternate modes.
All USB-C cables must be able to carry a minimum of 3 A current (at 20 V, 60 W) but can also carry high-power 5 A current (at 20 V, 100 W). USB-C to USB-C cables supporting 5A current must contain e-marker chips (also marketed as E-Mark chips) programmed to identify the cable and its current capabilities. USB charging ports should also be clearly marked with capable power wattage. Full-featured USB-C cables that implement USB 3.1 Gen 2 can handle up to 10 G bit/s data rate at full duplex. They are marked with a Super Speed+ (Super Speed 10 G bit/s) logo. There are also cables which can carry only USB 2.0 with up to 480 M bit/s data rate. There are USB-IF certification programs available for USB-C products, and end users are recommended to use USB-IF certified cables.
Devices may be hosts (with a downstream-facing port, DFP) or peripherals (with an upstream-facing port, UFP). Some, such as mobile phones, can take either role depending on what kind is detected on the other end. These types of ports are called Dual-Role-Data (DRD) ports, which was known as USB On-The-Go in the previous specification. When two such devices are connected, the roles are randomly assigned, but a swap can be commanded from either end, although there are optional path and role detection methods that would allow devices to select a preference for a specific role. Furthermore, dual-role devices that implement USB Power Delivery may independently and dynamically swap data and power roles using the Data Role Swap or Power Role Swap processes. This allows for charge-through hub or docking station applications where the USB-C device acts as a USB data host while acting as a power consumer rather than a source.
USB-C devices may optionally provide or consume bus power currents of 1.5 A and 3.0 A (at 5 V) in addition to baseline bus power provision; power sources can either advertise increased USB current through the configuration channel, or they can implement the full USB Power Delivery specification using both BMC-coded configuration line and legacy BFSK -coded V BUS line.
Audio Adapter Accessory Mode
A device with a USB-C port may support analog headsets through an audio adapter with a 3.5 mm jack, providing four standard analog audio connections (Left, Right, Microphone, and Ground). The audio adapter may optionally include a USB-C charge-through port to allow 500 MA devices charging. The engineering specification states that an analog headset shall not use a USB-C plug instead of a 3.5 mm plug. In other words, headsets with a USB-C plug should always support digital audio (and optionally the accessory mode).
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