USB-C: the one connector to rule them all. The compact design makes it compatible with even the slimmest mobile devices, while the dense pin-out (24 pins compared to USB Type A’s four) opens data and power transmission possibilities for extremely high-demand applications.
A USB-C port can theoretically replace ports for USB-A, USB-B, HDMI, DisplayPort, 3.5 mm audio, Ethernet, power, or all of the above, with total backward compatibility and up to 5V/240W of bi-directional power. Devices can be daisy-chained using multiple USB-C cables, massively simplifying cable management. And, of course, the Type-C connector is symmetrical, so there is no more rotating and mashing the USB connector into the port to get it inserted right-side-up. The era of true, plug-and-play connectivity has arrived!
Yeah… How’s that working out for you?
If you’ve struggled to get any benefit out of USB-C in your AV solutions, well, you’re not alone. It’s “a glorious mess,” and “as complex as any technology [IT professionals] deal with.” Running through that deceptively simple connector, there is an alphabet soup of confusingly named protocols and optional features.
A USB-C port might use any transfer mode ranging from USB 2.0, with its measly 4.5W of power and 48 Mbps of data, to USB4 Gen 4 (seriously, these names), with up to 240W of power and 80 Gbps. Intel’s Thunderbolt transport protocol uses the USB-C connector as well, but not all USB-C cables are Thunderbolt-compatible. Some USB-C ports are capable of multiple transfer modes, and many host devices have multiple USB-C ports, each with different capabilities: often you don’t even know what kind of signal you’re going to get until you hook up a couple of devices and watch what happens.
In the early days of USB-C, many tech professionals were burned by the inconsistent implementation of USB standards. The latest USB transport protocols can stand up to – and streamline – the most demanding AV applications, from 4K videoconferencing in home offices, to high-performance gaming and live streaming, to sophisticated media rooms. Despite the ease-of-use of the connector itself, though, it still takes a lot of research and QA to select the right components. Let’s examine what makes this “universal” connector more of a multiverse of madness.
USB-C Growing Pains
When USB-C was introduced in 2014, many device manufacturers leapt to adopt these powerful, streamlined ports. However, most adopters only enabled a limited set of USB features. In the early days, the vast majority of USB-C ports were configured only for power transmission and even that simple function was deceptively complicated. Though USB cables and chargers all look identical to the average consumer, many device manufacturers implemented proprietary fast-charging protocols that worked only with their own branded products. Mix and match brands, and the devices might still charge (albeit at a much slower than advertised rate) – or the charger might deliver an unexpectedly high wattage, damaging the host device.
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The versatile USB-C connector also allowed USB transfer modes to advance their capabilities dramatically—which in turn resulted in some very challenging distance limitations. For example, USB4 Gen 4 transfer mode can achieve up to 80 Gbps symmetric data transfer, or 120 Gbps asymmetric transfer, over a passive USB 3.1 Gen 2 Type-C cable — enough data and speed for an 8K video signal at 60 Hz — but the max distance is less than one meter. That might come as an unpleasant surprise to consumers who have no idea why the 10-foot cable they bought on Amazon doesn’t work. The fact that USB cable and transfer mode naming conventions are an impenetrable mess doesn’t help matters much.
Climbing the Hype Curve
Despite the vast delta between expectations and reality in early implementations, USB-C adoption has continued to pick up steam among manufacturers. COVID-19 played a big role in driving adoption forward: as millions of people scrambled to cobble together working offices and classrooms in their homes – and upgraded their home entertainment systems to keep themselves sane during lockdown – the benefits of unified connectivity snapped into focus for consumers and manufacturers alike. Education use cases were especially impactful: suddenly, a majority of U.S. school districts were furnishing students with Chromebooks for everyday learning. These lightweight devices needed fully featured USB-C ports to meet application demands. This perfect storm of need drove manufacturers to pour refreshed investment into USB-C.
As the USB Implementers Forum has released more and more powerful transfer modes, a growing number of products have expanded USB-C port functionality to include audio/video, variable bidirectional power delivery, data, and control. Alternative Modes (alt modes) are central to the expanding utility of USB-C. Alt modes dedicate some of the physical wires in a USB 3.1 cable to direct transmission of specific protocols. Currently, the USB Implementer’s Forum has five alt mode partners: DisplayPort, MHL, Thunderbolt, HDMI, and VirtualLink. Of these, DisplayPort and Thunderbolt are by far the most frequently implemented, though HDMI alt mode implementations are increasing, and transporting HDMI signals over USB-C via an adapter cable is already quite common.
Alt modes are optional. Commonly, devices with multiple USB-C ports will enable alt modes only on some of them, usually indicated by an alt mode partner logo next to the port. To work consistently, every link in the signal chain needs the proper alt mode support from host devices, ports, cables, and hubs. Still, with careful product qualification, it is now perfectly possible to use this one connector for a whole host of applications, including AV transport.
These Alt Modes offer very attractive signal transport options for monitors, projectors, or other external displays, especially as manufacturers have transitioned away from proprietary charging protocols to standard USB Power Delivery (USB PD). USB PD solves those early power problems by means of a chip embedded in the connector. Cables that support USB PD negotiate with any connected host and hub devices to determine their capabilities and deliver the right amount of power to each device. Power supply is bidirectional and configurable up to 48V, 5 A, and 240w. With these capabilities, a display can easily power a connected source, simplifying cable management. Of course, this is all dependent on using the right cables; if you’re using an older USB-C cable – one that lacks a chip or doesn’t advertise its power capabilities – then you’ll never get more than 15W over it.
Next Steps for USB-C
As USB-C marches toward ubiquity, its distance limitations are going to become a real problem. The USB Implementor’s Forum doesn’t specify a maximum cable length for USB 3.1 Type-C cables, but generally, passive cables should be no longer than 0.8m for USB4 Gen 4 transfer, and even active cables can rarely exceed 5m. On top of that, high-quality USB cables are wildly expensive. To reach true universality, there is a growing need for more extension options over Cat6A or fiber. Just like with HDMI before it, this increasingly ubiquitous (and stealthily complex) “plug and play” consumer connector is going to spawn whole new categories of professional products.
In the future, USB-C is going to be the most common port across phones, tablets, displays, computers, source devices, and more. It’s going to look simple, until you read the specs and realize that all of those ports have very different capabilities. USB has a variety of transfer modes, a range of optional features, and full backwards compatibility for a reason. Some devices have very limited power and data needs; consumers shouldn’t be forced to buy a $100 cable to charge their Fitbits.
Supporting collaboration, high definition displays, and other high-demand applications will require more sophisticated components. Don’t let the simple face of USB-C fool you or your clients. As we march into the USB-C era, be ready to do some deep product research and in-house testing to fully verify component capabilities and compatibility. Label everything; you don’t want your tech onsite mixing up the $10 cable and the $1000 cable.
For the moment, it seems, we live in an era of “almost-theres” and “not-quites” in the flux of an advancing technology. And, yet, the promise still holds: a single connector, capable of handling an array of tasks across numerous devices, without the chaos of tangled wires and incompatible plugs. We’re already living in the era of “one connector to rule them all.” Now, we just need the right mix of cables and extenders to bind them.
