Universal serial bus has been with us for so long, and has established such as extensive market penetration, as to have become nearly invisible. The power of that tiny connector rarely intrudes on our more challenging considerations we associate with the business of ongoing technological evolution. Aldous Huxley said “Most human beings have an almost infinite capacity for taking things for granted.” We almost certainly take the ability to charge our smartphones nearly anywhere for granted. We almost certainly take the ability to connect a tiny jump drive to nearly anything in order to share content for granted. We do so much with USB connectivity, we might just be taking it for granted!
USB is a directional technology. Because universal serial bus delivers power (5 volts up to 500 mA or more), this is necessary. The “A” end of a connection points to the upstream source and the “B” end connects to the downstream sink. Even the small micro-USB connections on smartphones and tablets have a A-to-B configuration. With the exception of some very limited circumstances, A-to-A cables are not used.
USB 1.1 was the genesis of the connector’s marketplace success. USB 1.1 arrived in 1998, followed quickly by USB 2.0 in 2001. USB 2.0 built upon, and includes, the foundation of USB 1.1. Together they remain ubiquitous. Supporting 1.5Mbit/s (Low speed), 12 Mbit/s (Full speed) and 480 Mbit/s (high speed) data transfer rates, these are the real core connections for advanced A/V control, interactivity and mobile device interface applications.
USB 2.0 has a length limitation that confines its use to a single-room design. Based on the propagation time and latency of electronics, the system has a hard limit of 16.5-feet (5 meters) for passive implementations. Specialized solutions can extend these limitations to 328-feet (100 meters). Advanced USB-over-IP solutions can remove even these restrictions (and will the subject of future articles).
In 2008, hot on the heels of the smartphone revolution and widespread inclusion of high definition video capability, USB 3.0 was introduced. USB 3.0 (now called USB 3.1 Gen 1) upped the transfer rate ante to 5 Gbit/s (SuperSpeed), more than a 10-fold improvement over USB 2.0. This speed came at a cost, however. The increased speed was achieved through a “dual link” topology that added an extra 5 pins to the nominal 4-pin USB 2.0 topology. The 9 pin connector allows for USB 2.0 devices to connect to 3.0 hosts, but prohibited new 3.0 devices from connecting to 2.0 hosts. Another hurdle is even more restrictive stricter length limitations. USB 3.0 link length, while not specifically bounded by the standard, rarely allows for more than 10-feet (3 meters) and is, for the most part, a desktop solution.
USB continues to evolve and will soon become one of our most powerful connectivity technologies, driving some of the most profound changes in mobile integration the communications industry will ever see. Formally known as USB 3.1 gen 2, this powerful technology increases data transfer rates to 10Gbit/s (SuperSpeed+). While retaining full backwards compatibility with USB 1.1, 2.0 and 3.0, USB 3.1 Gen 2 achieves its state-of-the-art performance through the use of a powerful new 24-pin form factor known as USB Type-C. Like USB-over-IP, we’ll be exploring this emerging powerhouse in upcoming articles.
Legrand is an industry leader in USB connectivity. Over the next few weeks we will take a closer look at some of our most popular USB connectivity solutions.