This article was written by Robin Cullen, Technical Director, PureLink GmbH on the history of the USB- leading to the unique problems USB-C has given us to solve.
Way back in the mid 90’s, the computer industry welcomed in yet another connector. However, this one was different. It was a simple four pin connector with comparatively pleasing haptics; it was very unlike the clunky multi pin D-Type connections that were so common back then. The “Universal Serial Bus” or USB 1.0 as it came to be known, promised a unified method for sending simple serial data from a range of new peripheral devices. In its first iteration, only very low speed HID devices such as joysticks, mice, keyboards and maybe some printers were compatible and as with most things, the first version did not work that well.
Version 2.0 however was a big improvement. With the previous version’s bugs fully ironed out and a boost in speed and power, it offered an incredibly useful set of abilities that quickly resulted in USB ports being found on all sorts of products across a broad range of sectors. USB had found its feet. The USB port quickly replaced almost all other peripheral ports on IT hardware and became the go-to connector for powering, charging, and exchanging data in the burgeoning mobile device market.
Version 3.X – a Master Class in How Not to Name Your Product
It seems, version 3.0 was developed somewhat ahead of the market need for its 5Gbps bandwidth capabilities and apart from storage transfer devices, not many products made use of it initially. Perhaps that was part of the reason for the later changes and chaotic updates, but this lack of adoption was also partly due to the much larger and unwieldy B connectors needed to transfer the high bandwidth data.
From the release of the v3.0 up to where we are now, with the arrival of USB4, lies an unmitigated mess of names changes and confusion. Over the last few years, USB has changed the names for what is basically the same thing, four times! It is hard to find another example of chaos like it in any industry and it is equally hard to imagine, that no one has been fired at their head office for this fiasco. It has left engineers and users alike, in a state of utter confusion. Product descriptions look wrong or out of date despite the fact nothing of consequence has changed. You would be forgiven for thinking that a cable described as USB3.0 is not as good as a cable described as USB3.2 Gen1 despite them having the exact same basic specification.
However out of the darkness of ineptitude, came a shining ray of light; the USB-C connector.
Game Changing Connections, but Read the Fine Print
USB-C offers a host of capabilities which truly make it the next generation of connection standards. The goal of the USB-C connector is to provide a universal cable for all media, and USB-C definitely has the technology to achieve this. Just like the Lightning cable from Apple it is reversible which adds a new level of usability to the user experience. Previous versions of USB required a Host/Device relationship that meant one product must have a USB-A port and one product must have a USB-B port. USB-C does away with this and by actively communicating between devices, works out what role each product should have. It goes further than that though. With USB-C the door is thrown open to all manner of possibilities. Because of the intelligent communication that is possible between devices, pins of the connection can be dynamically re-assigned to other tasks. Suddenly variable power delivery, video transmission and simultaneous high-speed data all become available to the user, all seemingly without effort thanks to alt mode and other clever additions such as e-marking of cables. Before USB-C, it would have been unthinkable to vary the voltage from 5V up to 20V, but it is not only possible with USB-C it is quickly becoming a world standard for all mobile devices from mobile phones up to high powered laptops.
So, what is the problem? It sounds like we have found an almost utopian cable standard, right?
Well almost. The devil, as always, is in the details. Below are the three main bear-traps to avoid when setting up a USB-C system.
Cable Spec. Theoretically, provided you have acquired the best quality cable available, a plug-and-play experience will very likely occur; the specification is solid, and when cables are made strictly to the spec like PureLink cables are, they work superbly. However, it is entirely possible to buy a USB2.0 charging cable with USB-C connectors at both ends that is completely indistinguishable from a USB4 40Gbps cable. If you accidentally use the charging cable with your device and nothing happens, how do you know what the problem is? Can the man in the street tell by looking at the cable what it can, and more importantly, cannot do? 99% of the time the answer is no, even if the cable is marked, which they often are not.
Reversibility. For the end user, a reversible connector is great, not so much for an installer though. Quite often in an installation, AV professionals must use patch panels or wall plates to connect the user environment to out-of-site equipment. With USB-C this becomes very hard to achieve. Normal practise would be a short cable for the user, then a female-female wall connection (a keystone for example) then a short cable to the device. However, this scenario is not possible with USB-C; because of the reversible nature of the cable, a communication failure can occur during the handshake if there is a female/female connection. Only direct cable connections with no breaks are 100% guaranteed to work.
Range. To make the most of all the benefits of USB-C connectivity, you need to be right up close and personal with your devices. Anything above one and a half meters of cable length and you will start to see loss of bandwidth. Range is a problem with a lot of protocols like HDMI and DisplayPort, and active repeaters and extenders are available to extend the range to suit the installations needs. Unfortunately, with all of USB-C’s different modes, coupled with the reversibility of the connector and power delivery requirements, the industry is struggling to find active products that exactly mimic the behaviour of a passive cable. The solutions available at the moment are often fixed as “Video only” or “Data only” and almost nothing with USB Power Delivery. We at PureLink are closest to getting there with our fully compatible PI6000 series active USB-C cable with 60W charging over up to five meters, but new technologies are needed to reach very long distances.
With all that said, and if the pitfalls are avoided, the USB-C protocol has and will continue to improve user experiences. The newer fourth generation versions of USB and Thunderbolt use USB-C exclusively and are only the beginning. We can expect this revolutionary connector to become even more prevalent in the future.