USB-C

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USB-C
LeTV X600 USB Type C port.jpg
USB-C port on a smartphone.
Type Digital audio/video/data connector/power
Designer USB Implementers Forum
Designed August 2014 (published)

USB Type-C, commonly known as simply USB-C, is a 24-pin USB connector system allowing transport of data and energy. It is distinguished by its horizontally symmetrical "reversible" connector.[1]

The USB Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014.[2] It was developed at roughly the same time as the USB 3.1 specification.

A device that implements USB-C does not necessarily support USB 3.1, USB Power Delivery, or Alternate Mode.[3][4]

Details[edit]

USB type C USB-C type c

The USB-C connectors connect to both hosts and devices, replacing various USB-B and USB-A connectors and cables with a standard meant to be future-proof.[5][6] The 24-pin double-sided connector is slightly larger than the micro-B connector, with a USB-C port measuring 8.4 millimetres (0.33 in) by 2.6 millimetres (0.10 in). The connector provides four power/ground pairs, two differential pairs for non-SuperSpeed data (though only one pair is populated in a USB-C cable), four pairs for SuperSpeed data bus (only two pairs are used in USB 3.1 mode), two "sideband use" pins, VCONN +5 V power for active cables, and a configuration pin used for cable orientation detection and dedicated biphase mark code (BMC) configuration data channel.[7][8][9]

Connecting an older device to a host with a USB-C receptacle requires a cable or adapter with a USB-A or USB-B plug or receptacle on one end and a USB-C plug on the other end. Legacy adapters with a USB-C receptacle are "not defined or allowed" by the specification because they can create "many invalid and potentially unsafe" cable combinations.[10]

Devices[edit]

Devices may be hosts or peripherals. 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). When two such devices are connected, the roles are randomly assigned but a swap can be commanded from either end. Furthermore, dual-role devices that support 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 Type-C device acts as a USB data host while acting as a power consumer rather than a source.[4]

USB-C devices may optionally support 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 support the full USB Power Delivery specification using both BMC-coded configuration line and legacy BFSK-coded VBUS line.[4][11]

Cables[edit]

USB-C 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 Gen2.[12] Electronic ID chip provides information about product/vendor, cable connectors, USB signalling protocol (2.0, Gen1, Gen 2), passive/active construction, use of VCONN power, supported VBUS current, latency, RX/TX directionality, SOP controller mode, and hardware/firmware version .[4]

USB-C 2.0 cables do not have shielded SuperSpeed pairs, sideband use pins, or additional wires for power lines. Increased cable lengths up to 4 m are supported.

All USB-C cables must support a minimum of 3 A current (up to 60 W @20V) but can also support high-power 5 A current (up to 100 W). All USB-C to USB-C cables must contain e-marker chips programmed to identify the cable and its current capabilities. USB Charging ports should also be clearly marked with supported power wattage.[11]

Full-featured USB-C cables that support USB 3.1 Gen 2 can handle up to 10 Gbit/s data rate at full duplex. They are marked with a SuperSpeed+ (SuperSpeed 10 Gbit/s) logo. There are also cables which support only USB 2.0 with up to 480 Mbit/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.[13]

Modes[edit]

Audio Adapter Accessory Mode[edit]

USB-C plug supports analog headsets through an audio adapter accessory with a 3.5 mm socket providing four standard analog audio signals (Left, Right, Mic, and GND). The audio adapter may optionally include a USB-C pass-through plug to allow 500 mA device charging. The engineering specification states that a 3.5 mm analog headset jack should not replace a USB-C plug.[14]

Analog signals use the USB 2.0 positive differential pair (Dp) and the two side-band use pairs. The presence of the audio accessory is signalled through the configuration channel and VCONN.

Alternate Mode[edit]

An Alternate Mode dedicates some of the physical wires in a USB-C 3.1 cable for direct device-to-host transmission of alternate data protocols. The four high-speed lanes, two side-band pins, and (for dock, detachable device and permanent cable applications only) two non-SuperSpeed data pins and one configuration pin can be used for alternate mode transmission. The modes are configured using vendor-defined messages (VDM) through the configuration channel.

Specifications[edit]

USB Type-C Specification 1.0[edit]

Connector pinouts[edit]

Type-C plug and receptacle pinouts
Pin Name Description Pin Name Description
A1 GND Ground return B12 GND Ground return
A2 SSTXp1 SuperSpeed differential pair #1, TX, positive B11 SSRXp1 SuperSpeed differential pair #2, RX, positive
A3 SSTXn1 SuperSpeed differential pair #1, TX, negative B10 SSRXn1 SuperSpeed differential pair #2, RX, negative
A4 VBUS Bus power B9 VBUS Bus power
A5 CC1 Configuration channel B8 SBU2 Sideband use (SBU)
A6 Dp1 Non-SuperSpeed differential pair, position 1, positive B7 Dn2 Non-SuperSpeed differential pair, position 2, negative[a]
A7 Dn1 Non-SuperSpeed differential pair, position 1, negative B6 Dp2 Non-SuperSpeed differential pair, position 2, positive[a]
A8 SBU1 Sideband use (SBU) B5 CC2 Configuration channel
A9 VBUS Bus power B4 VBUS Bus power
A10 SSRXn2 SuperSpeed differential pair #4, RX, negative B3 SSTXn2 SuperSpeed differential pair #3, TX, negative
A11 SSRXp2 SuperSpeed differential pair #4, RX, positive B2 SSTXp2 SuperSpeed differential pair #3, TX, positive
A12 GND Ground return B1 GND Ground return
  1. ^ a b There is only a single Non-SuperSpeed differential pair in the cable. This pin is not connected in the plug/cable.
USB Type-C receptacle pinout end-on view
USB Type-C plug pinout end-on view

Cable wiring[edit]

Full-featured USB 3.1 and 2.0 Type-C cable wiring
Plug 1, USB Type-C USB Type-C cable Plug 2, USB Type-C
Pin Name Wire colour No Name Description 2.0[a] Pin Name
Shell Shield Braid Braid Shield Cable external braid Shell Shield
A1, B12,
B1, A12
GND Tin-plated 1 GND_PWRrt1 Ground for power return A1, B12,
B1, A12
GND
16 GND_PWRrt2
A4, B9,
B4, A9
VBUS Red 2 PWR_VBUS1 VBUS power A4, B9,
B4, A9
VBUS
17 PWR_VBUS2
B5 VCONN Yellow
18 PWR_VCONN VCONN power, for active cables[b] B5 VCONN
A5 CC Blue 3 CC Configuration channel A5 CC
A6 Dp1 White 4 UTP_Dp[c] Unshielded twisted pair, positive A6 Dp1
A7 Dn1 Green 5 UTP_Dn[c] Unshielded twisted pair, negative A7 Dn1
A8 SBU1 Red 14 SBU_A Sideband use A B8 SBU2
B8 SBU2 Black 15 SBU_B Sideband use B A8 SBU1
A2 SSTXp1 Yellow[d] 6 SDPp1 Shielded differential pair #1, positive B11 SSRXp1
A3 SSTXn1 Brown[d] 7 SDPn1 Shielded differential pair #1, negative B10 SSRXn1
B11 SSRXp1 Green[d] 8 SDPp2 Shielded differential pair #2, positive A2 SSTXp1
B10 SSRXn1 Orange[d] 9 SDPn2 Shielded differential pair #2, negative A3 SSTXn1
B2 SSTXp2 White[d] 10 SDPp3 Shielded differential pair #3, positive A11 SSRXp2
B3 SSTXn2 Black[d] 11 SDPn3 Shielded differential pair #3, negative A10 SSRXn2
A11 SSRXp2 Red[d] 12 SDPp4 Shielded differential pair #4, positive B2 SSTXp2
A10 SSRXn2 Blue[d] 13 SDPn4 Shielded differential pair #4, negative B3 SSTXn2
  1. ^ USB 2.0 Type-C cables do not include wires for SuperSpeed or Sideband use.
  2. ^ VCONN must not traverse end-to-end through the cable. Some isolation method must be used.
  3. ^ a b There is only a single differential pair for non-SuperSpeed data in the cable, which is connected to A6 and A7. Contacts B6 and B7 should not be present in the plug.
  4. ^ a b c d e f g h Wire colours for differential pairs are not mandated.

Related USB-IF specifications[edit]

As outlined by the USB Type-C Cable and Connector Language Usage Guidelines,[15] if a product implements USB Type-C, it does not necessarily implement USB 3.1 or USB Power Delivery.

USB 2.0 Billboard Device Class specification[edit]

USB 2.0 Billboard Device Class is defined to communicate the details of supported Alternate Modes to the computer host OS. It provides user readable strings with product description and user support information. Billboard messages can be used to identify incompatible connections made by users. They are not required to negotiate Alternate Modes and only appear when negotiation fails between the host (source) and device (sink).

USB Audio Device Class 3.0 specification[edit]

USB Audio Device Class 3.0 defines powered digital audio headsets with a USB-C plug.[4]

Alternate Mode partner specifications[edit]

As of 2016 four system-defined Alternate Mode partner specifications exist. Additionally, vendors may support proprietary modes for use in dock solutions.

List of Alternate Mode partner specifications
Name Date Protocol
DisplayPort Alternate Mode published in September 2014 DisplayPort 1.3[16][17]
MHL Alternate Mode announced in November 2014[18] MHL 1.0, 2.0, 3.0 and superMHL 1.0[8][19][20][21]
Thunderbolt Alternate Mode announced in June 2015[22] Thunderbolt 3 (includes DisplayPort 1.2 Alternate Mode)[22][23][24][25]
HDMI Alternate Mode announced in September 2016[26] HDMI 1.4b[27][28][29][30]

Other serial protocols like PCI Express and Base-T Ethernet[31] are possible.[citation needed]

Alternate Modes are optional USB Type-C features and devices are not required to support any specific Alternate Mode. The USB Implementers Forum is working with its Alternate Mode partners to make sure that ports are properly labelled with respective logos.[32]

Alternate Mode hosts and sinks can be connected with either regular full-featured USB-C cables, or converter cables/adapters:

USB 3.1 Type-C to Type-C full-featured cable
DisplayPort, MHL, HDMI and Thunderbolt (20 Gbit/s) Alternate Mode USB-C ports can be interconnected with standard passive full-featured USB Type-C cables. These cables are only marked with standard "trident" SuperSpeed USB logo (for Gen 1 cables) or the SuperSpeed USB 10 Gbit/s logo (for Gen 2 cables) on both ends.[33] Cable length should be 2.0 m or less for Gen 1 and 1.0 m or less for Gen 2.
USB 3.1 Type-C to Type-C active cable
Thunderbolt 3 (40 Gbit/s) Alternate Mode requires active USB Type-C cables that are certified and electronically marked for high-speed ThunderBolt 3 transmission, similarly to high-power 5 A cables.[22][25] These cables are marked with standard "trident" SuperSpeed 10 Gbit/s logo and a Thunderbolt logo on both ends.[33]
USB 3.1 Type-C adapter cable (plug) or adapter (socket)
These cables/adapters contain a valid DisplayPort, HDMI, or MHL plug/socket marked with the logo of the required Alternate Mode, and a Type-C plug with a "trident" SuperSpeed 10 Gbit/s logo on the other end. Cable length should be 0.15 m or less.

Active cables/adapters contain powered ICs to amplify/equalise the signal for extended length cables, or to perform active protocol conversion. The adapters for video Alt Modes may allow conversion from native video stream to other video interface standards (e.g., DisplayPort, HDMI, VGA or DVI).

Using full-featured USB-C cables for Alternate Mode connections provides some benefits. Alternate Mode does not employ USB 2.0 lanes and the configuration channel lane, so USB 2.0 and USB Power Delivery protocols are always available. In addition, DisplayPort and MHL Alternate Modes can transmit on one, two, or four SuperSpeed lanes, so two of the remaining lanes may be used to simultaneously transmit USB 3.1 data.[34]

Alternate Mode protocol support matrix for USB 3.1 Type-C cables, adapter cables and adapters
Mode Type-C cable[nb 1] Adapter Construction
USB[nb 2] DisplayPort Thunderbolt superMHL HDMI HDMI DVI-D Component video
3.1 1.2 1.3 20 Gbit/s 40 Gbit/s 1.4b 1.4b 2.0b single-link dual-link (YCbCr, VGA/DVI-A)
DisplayPort Yes Yes Does not appear No Passive
Optional Optional Yes Yes Yes Active
Thunderbolt Yes Yes Does not appear Yes Yes[nb 3] Does not appear No Passive
Optional Optional Optional Yes Yes Yes Yes Active
MHL Yes Does not appear Yes Does not appear Yes No Yes No No Passive
Optional Optional Does not appear Yes Does not appear Yes Active
HDMI Does not appear Yes Yes No Yes No No Passive
Optional Does not appear Yes Active
  1. ^ USB 2.0 and USB Power Delivery are available at all times in a Type-C cable
  2. ^ USB 3.1 can be transmitted simultaneously when the video signal bandwidth requires two or fewer lanes
  3. ^ Thunderbolt 3 40 Gbit/s Passive cables are only possible <0.5m due to limitations of current cable technology.

Software support[edit]

  • Linux has supported USB 3.0 since kernel version 2.6.31 and USB version 3.1 since kernel version 4.6.
  • Windows 10 and Windows 10 Mobile support USB 3.1, USB-C, alternate modes, billboard device class, power delivery, audio accessory, and USB Dual-Role support.[35]
  • Windows 8.1 added USB-C and billboard support in an update.[36]
  • OS X Yosemite supports USB 3.1, USB-C, alternate modes, and power delivery.[37]
  • Android Marshmallow works with USB 3.1 and USB-C.[38]
  • Chrome OS supports USB 3.1 and USB-C starting with the Chromebook Pixel 2015 and supports alternate modes, power delivery, and USB Dual-Role support.[39]

Hardware support[edit]

An increasing number of motherboards, notebooks, tablet computers, smartphones, hard disk drives, USB hubs and other devices released from 2014 onwards feature USB-C receptacles.

Currently, DisplayPort is the most widely implemented alternate mode, and is used to provide video output on devices such as MacBook, Chromebook Pixel, HTC U11, Samsung Galaxy S8, Samsung Galaxy TabPro S, Microsoft Lumia 950, and the Nintendo Switch. A USB-C multiport adapter converts the device's native video stream to DisplayPort/HDMI/VGA, allowing it to be displayed on an external display, such as a television set or computer monitor.

Examples of devices that support high-power charging according to the USB Power Delivery specification include MacBook, Chromebook Pixel, Dell Venue 10 Pro, Lenovo ThinkPad X1, Nintendo Switch, Nexus 5X, Nexus 6P, Google Pixel, Samsung Galaxy TabPro S, Samsung Galaxy S8, LG G6, and Moto Z.

Power issues with non-compliant accessories[edit]

Some non-compliant cables with a USB-C connector on one end and a legacy USB-A plug or Micro-B receptacle on the other end incorrectly terminate the Configuration Channel (CC) with a 10kΩ pullup to VBUS instead of the specification mandated 56kΩ pullup[40], causing a device connected to the cable to incorrectly determine the amount of power it is permitted to draw from the cable. Cables with this issue may not work properly with certain products, including Apple and Google products, and may even damage power sources such as chargers, hubs, or PC USB ports.[41][42]

References[edit]

  1. ^ Hruska, Joel (2015-03-13). "USB-C vs. USB 3.1: What's the difference?". ExtremeTech. Retrieved 2015-04-09. 
  2. ^ Howse, Brett (2014-08-12). "USB Type-C Connector Specifications Finalized". Retrieved 2014-12-28. 
  3. ^ "USB Type-C Cable and Connector : Language Usage Guidelines from USB-IF" (PDF). Usb.org. Retrieved 2015-06-18. 
  4. ^ a b c d e "USB Type-C Overview" (PDF). usb.org. USB-IF. 2016-10-20. 
  5. ^ Ngo, Dong. "USB Type-C: One cable to connect them all". CNET. Retrieved 2015-06-18. 
  6. ^ "USB Type-C Connector Specifications Finalized". AnandTech.com. Retrieved 2015-06-18. 
  7. ^ "Technical Introduction of the New USB Type-C Connector". Intel.ActiveEvents.com. Retrieved 2015-06-18. 
  8. ^ a b "MHL Alternate Mode reference design for superMHL over USB Type-C". AnandTech.com. 2016-03-15. Retrieved 2015-06-18. 
  9. ^ "Introduction to USB Type-C" (PDF). Microchip.com. Retrieved 2015-06-18. 
  10. ^ Universal Serial Bus Type-C Cable and Connector Specification Revision 1.1 (April 3, 2015), section 2.2, page 20
  11. ^ a b "USB Power Delivery" (PDF). usb.org. USB-IF. 2016-10-20. 
  12. ^ Universal Serial Bus Type-C Cable and Connector Specification Revision 1.2 (March 25, 2016), Table 3-1, page 27
  13. ^ "USB Compliance and Certification" (PDF). usb.org. USB-IF. 2016-10-20. 
  14. ^ Universal Serial Bus Type-C Cable and Connector Specification Revision 1.2 (March 25, 2016), section A.1, page 194
  15. ^ "USB Type-C Cable and Connector : Language Usage Guidelines from USB-IF" (PDF). Usb.org. Retrieved 2015-06-18. 
  16. ^ "VESA® Brings DisplayPort™ to New USB Type-C Connector". DisplayPort. 2014-09-22. Retrieved 2015-06-18. 
  17. ^ "DisplayPort Alternate Mode on USB-C - Technical Overview" (PDF). usb.org. USB-IF. 2016-10-20. 
  18. ^ "MHL® – Expand Your World". MHLTech.org. Retrieved 2015-06-18. 
  19. ^ "MHL Releases Alternate Mode for New USB Type-C Connector". MHLTech.org. MHLTech.org. 2014-11-17. Retrieved 2015-06-18. 
  20. ^ "MHL Alternate Mode over USB Type-C to support superMHL". www.mhltech.org. www.mhltech.org. 2015-01-06. Retrieved 2016-11-15. 
  21. ^ "MHL Alt Mode: Optimizing Consumer Video Transmission" (PDF). usb.org. MHL, LLC. 2015-11-18. Archived from the original on 14 September 2016. 
  22. ^ a b c "Thunderbolt 3 – The USB-C That Does It All | Thunderbolt Technology Community". Thunderbolttechnology.net. Retrieved 2015-06-18. 
  23. ^ One port to rule them all: Thunderbolt 3 and USB Type-C join forces, retrieved 2015-06-02 
  24. ^ Thunderbolt 3 is twice as fast and uses reversible USB-C, retrieved 2015-06-02 
  25. ^ a b Anthony, Sebastian (2015-06-02). "Thunderbolt 3 embraces USB Type-C connector, doubles bandwidth to 40Gbps". Ars Technica UK. 
  26. ^ "HDMI Press Release: HDMI Releases Alternate Mode for USB Type-C™ Connector". hdmi.org. 
  27. ^ "HDMI LLC - HDMI Over USB Type-C" (PDF). usb.org. HDMI LLC. 2016-10-20. 
  28. ^ "HDMI Alt Mode for USB Type-C Announced". anandtech.com. 
  29. ^ "A new standard will allow your USB-C devices to connect to HDMI". neowin.net. 
  30. ^ "HDMI Alt Mode for USB Type-C™ Connector". hdmi.org. 
  31. ^ "[802.3_DIALOG] USB-C Ethernet Alternate Mode". ieee. 2015-03-26. 
  32. ^ Cunningham, Andrew (2015-01-09). "USB 3.1 and Type-C: The only stuff at CES that everyone is going to use | Ars Technica UK". ArsTechnica.co.uk. Retrieved 2015-06-18. 
  33. ^ a b "USB Logo Usage Guidelines" (PDF). usb.org. USB-IF. 2016-03-11. 
  34. ^ "VESA® Brings DisplayPort™ to New USB Type-C Connector | VESA". www.vesa.org. Retrieved 2016-12-11. 
  35. ^ Microsoft. "Windows support for USB Type-C connectors". Microsoft MSDN. Retrieved 2015-09-30. 
  36. ^ Microsoft. "Update for USB Type-C billboard support and Kingston thumb drive is enumerated incorrectly in Windows". Retrieved 2015-12-08. 
  37. ^ "Using the USB-C port and adapters on your MacBook (Retina, 12-inch, Early 2015) - Apple Support". Support.Apple.com. 2015-05-28. Retrieved 2015-06-18. 
  38. ^ "Android – Marshmallow". Retrieved 2015-10-12. 
  39. ^ "Charge your Chromebook Pixel (2015)". Retrieved 2015-10-31. 
  40. ^ Universal Serial Bus Type-C Cable and Connector Specification Revision 1.1 (April 3, 2015), page 60, table 3-13, note 1
  41. ^ Kif Leswing (2015-11-05). "Google Engineer Reviews Defective USB Cables on Amazon - Fortune". Fortune. 
  42. ^ "In response to the Type-C cable discussions". 

External links[edit]

  • The Universal Serial Bus Type-C Cable and Connector Specification is included in a set of USB documents which can be downloaded from USB.org.