Tech 101: USB Type-C - An Introduction

By Jamshed Avari | Updated: 31 March 2015 13:17 IST

USB Type-C, the supposedly magical new standard that promises to solve all our connectivity problems, is finally real and ready for mainstream use. Type-C has been in development for a while - we first heard about it over a year ago and first saw it in action at CES in January. Now, with the high-profile launch of Apple's new ultra-minimalist MacBook, Type-C has gone public in a big way.

Type-C is meant to be able to work with all kinds of devices. More importantly, the same plug will be used on both sides of the cable and it is symmetrical so it can go in no matter which way is up. Users are often frustrated by USB plugs because they can't tell with a glance which way they should fit. Type-C was designed with exactly that in mind.

But there's a lot more going on under the hood, and there are going to be new problems. For starters, laptops can be charged using Type-C just like phones and tablets use USB today, but not all hosts will be able to deliver that much power. Type-C will replace dedicated HDMI, DisplayPort and VGA video outputs on many devices, but that doesn't mean all devices with Type-C can be plugged into screens or projectors.

If you're wondering what exactly this new standard means for you, we have all the answers.

The new USB Type-C connector in all its glory.

The background
USB 1.0 and 1.1 ports first started appearing on PCs in the late 1990s and it didn't take very long for the new standard catch on. USB provided an alternative to the mess of serial, parallel, PS/2 and MIDI ports a PC user typically had to deal with, but its most attractive feature was the ability to hot-plug devices. This meant that users did not have to shut down their PCs before making hardware changes, as had been the norm. Data transfer speed topped out at 12Mbps, which was enough for things like input devices and printers.

USB 2.0, which debuted in the early 2000s, raised the speed to 480Mbps, ushering in a whole new generation of storage devices and peripherals. This is when USB emerged as a viable standard for transferring data to and from devices such as portable media players and mobile phones. Battery charging was a natural extension, and so the standard evolved to improve power delivery. Experiments were made towards a wireless USB standard, but did not really go anywhere due to power requirements and limited flexibility.

USB 3.0 came out in 2008 in response to standards such as FireWire and eSATA that were better at high-speed bi-directional data transfers. Peak theoretical speed was raised to 5Gbps and for the first time, new cables and sockets were required. USB 3.0 ports and plugs were designed to be backwards compatible with older devices, which increased their size and cost to implement. However, there was no major disruption and users were not confused.

USB 3.0 Type-A plug (top-left), USB 3.0 Type-B plug (top-right), USB 3.0 micro-B plug (bottom-left), and USB Type-C and Type-A ports (bottom-right).

Less than five years later, USB 3.1 was released to double the peak speed to 10Gbps, using the same plugs and ports as USB 3.0. At this point the standard changed again, but not the connectors.

To make things a little more interesting, the label "USB 3.1" now applies retrospectively to 5Gbps USB 3.0 connections as well. The terms "USB 3.1 Gen 1" and "USB 3.1 Gen 2" are being used to refer to 5Gbps and 10Gbps implementations respectively. Apple, for instance, describes the 5Gbps Type-C port on its new Macbook as USB 3.1 which is technically correct but also somewhat disingenuous.

It's impossible to imagine a world without USB - we would still have to depend on special-purpose plugs and ports for each kind of device. Charging devices, syncing data and transporting anything would be a nightmare of incompatibilities. In the age of USB, we have largely done away with installing drivers and rebooting each time we plugged a new device in to our PC - and if you can't remember an age when this was the norm, consider yourself very lucky indeed.

Introducing USB Type-C
First of all, Type-C is not a new version of USB and does not replace USB 3.0 or 2.0. Type-C refers to the plug itself, and it is just a new possible interface for USB 3.1 (which now encompasses USB 3.0 as well). USB 3.1 will also be implemented with traditionally shaped USB ports and cables. Type-C will very commonly be associated with USB 3.1 but it is by no means guaranteed that a device supporting USB 3.1 speeds will use the Type-C connector, and vice versa.

Type-C will supplant the Type-A and Type-B connector types, which have until now been used to define the roles of USB host and target devices respectively. Standard USB cables were designed to have different connectors on either end to prevent people from doing things such as plugging one printer into another and expecting them to work without anyone sending print commands. Worse, people might have plugged two power sources into each other. It's for this exact reason that power cables have always had different plugs on each end - and so such problems have rarely arisen, if ever.

Over the years, Mini-B and then Micro-B emerged to cater to increasingly smaller devices (more commonly known as Mini-USB and Micro-USB respectively). However, at the same time, devices once intended to be targets began to take on aspects of host devices. We wanted to be able to plug pen drives into smartphones, print directly from storage devices, and use touchscreen tablets as control surfaces, amongst other things. USB On-the-Go (OTG) allowed devices to host other target devices through their Type-B ports. However, dongles were needed because of the different port shapes, which meant the potential of the technology was rarely realised.

Now, we'll be able to plug anything in to anything else. Theoretically, devices will sense each other and clearly establish what they expect of each other in terms of charging, control and data exchanges. Incompatible products just won't work - people will still get frustrated, but hopefully not too much. In this sense, Type-C trades one set of problems for another.

In Part 2, we get into Alternate Modes and enhanced power delivery, which are unique to Type-C, and take a look at some of the hardware that will soon be commonplace.

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