What are the different kinds of USB C-to-C cables?
Now that everyone has more and more #USB #TypeC
phones, tablets, and laptops and we’re getting more and more USB Type-C hubs and chargers, let’s talk a little bit about C-to-C cables. Not Legacy. :)
The USB Type-C Specification (available here : http://www.usb.org/developers/docs/usb_31_032516.zip
) defines 2 different kinds of C-to-C cables. I've listed the parts of the spec for convenience in reading.
What are the major differences between these two kinds of cables?Section 3.4.1
: USB Full-Featured Type-C Cable Assembly -
This type supports USB 3.1 functionality up to 10gbps. This kind of cable requires between 15 and 18 wires in total.
As an additional requirement, these cables are now required in the Type-C spec to have e-marker identifier chips, increasing the complexity and cost of this kind of cable.Section 3.4.2
: USB 2.0 Type-C Cable Assembly -
This type of cable only supports USB 2.0 High Speed operation.
It has a total of 5 or 6 wires. Most typical is 5 wires, Gnd, Vbus, CC, and Dp, Dn.
This kind of cable's e-marker is optional.
The USB 3.1 Full Featured cables have 10 more wires than the USB 2.0 variant. With those extra wires, the cable is capable of faster USB 3.1 data rates with supported hosts and clients, meaning support for SuperSpeed 5gbps and SuperSpeed+ 10gbps. See the pictures I’ve attached below of two tables from the Type-C spec that illustrate this stark difference in the number of wires.
In addition, these extra wires make Alternate Modes
such as VESA DisplayPort possible. Type-C alternate modes allow for some or all of the SuperSpeed data wires and other wires in the full-featured cable to be switched over to a different purpose other than USB data. In the case of VESA DP alternate mode, these are switched over to allow DisplayPort video traffic. This means that the Full-Featured Type-C cable above isn’t just a replacement for your USB 3.1 A-to-B cable, but it also represents a complete replacement of DisplayPort cables or HDMI cables as well!
USB 2.0 cables cannot support this functionality, but they are simpler and far cheaper for the manufacturer. They also have several very important advantage over Full Featured cables : 1) It’s WAY easier to get much longer cables when they are USB 2.0. The 8 superspeed wires must meet USB 3.1 signal integrity requirements, which get harder as the cable length grows. USB 2.0 cables don’t have that problem and easily get to 2M or 3M.
2) Since there are fewer wires, USB 2.0 cables will be thinner and more flexible than their USB 3.1 Full-Featured cable variants.Differentiation
How are we as consumers going to tell these two kinds of cables apart? Unlike in previous generations of USB connectors, where the connectors are all different based on the capabilities of the cable, both of these types of cables may look identical based on the plugs on each end. The USB-IF’s solution to the possible confusion to these different cables is careful labeling with new logos. If a C-to-C cable is labeled clearly with the SuperSpeed USB trident logo (with a “SS”), then that cable should be guaranteed to be a Full-Featured cable. Otherwise, expect the cable to be USB 2.0 only.
I’ve posted pictures of two different USB Type-C cables from each class of cable above. The first is Google’s 1.8M USB 2.0 C-to-C cable. The second is Black Squid’s Full-Featured USB 3.1 C-to-C cable.#USBC