What You Need to Know About USB

What Integrators Need to Know About USB

Keeping up with all the changes and updates relative to Universal Serial Bus — more commonly known as USB — architecture isn’t always easy. In fact, it has been a bit of a long, winding road, which was first paved back in 1994. Initially, USB was developed to serve as a single connector that could replace several connectors found on PCs. The goal was to simplify the software configuration of all devices that could connect through USB and enable faster data rates for a range of external devices.

But given all the acronyms and the updates to data-transfer speed rates among USB standards, it’s no wonder that some system designers and integrators are left scratching their heads. Here, we hope to disambiguate all things USB to help integrators gain a firmer footing.

“There have been several speed and interface changes, so it’s almost like they went out of their way to be confusing about it,” quips Chris Poulin, vice president of BTX Technologies. “For people who don’t understand, it’s understandable [that they don’t]. Even many systems designers are getting confused.”

Fortunately, Poulin himself has kept up, as has Jason Harbst, technical sales support/project registration supervisor for ADI, on whose knowledge we’ll lean. In the paragraphs that follow, Poulin and Harbst will share insights on USB to help security and AV integrators up their USB IQ and, in the process, better navigate the changing technology landscape.

Chronology of USB

A detailed understanding of evolution rests upon a firm grasp of the past. Thus, we’ll start with a chronology of USB:

Taking the confusion out of USB-C

USB-C is a reversible connector that can be used to transmit data, video and audio signals, and PCI-E signals. It is the most recent iteration of the USB interface’s connector. Harbst points out that, because it is flippable, it doesn’t matter which way you plug it in. “USB-C will connect [regardless],” he explains, “whereas the traditional one was rectangular and only went in one way. It doesn’t matter with USB-C. It is the preferred connection; it’s easier and smaller.”

USB-C supports previous USB standards and can support third-party protocols such as DisplayPort and HDMI in Alternate Mode. “It will work with other video adapters like HDMI,” Harbst notes. “It’s a very adaptable type of connection.”

“There are several different styles of USB,” Harbst affirms. “So, it’s important to make sure that, whatever type of cable and style it is, [it] will meet the needs of your equipment.”

He continues, “The labeling should be reliable.” Harbst also warns of the limitations inherent in buying a cheap cable, saying that the data-transfer capabilities, speed and power may not be adequate.

USB.org, a site sponsored by USB Implementers Forum, Inc., creator of USB technology, notes that all USB-C-to-USB-C cables must now be marked with either a power capability of 60W or 240W, as well as the appropriate data rate that a cable supports, in order to pass through the USB-IF Compliance Program.

Battling length limitations

“On the AV side, in terms of videoconferencing, a lot of these systems involve a camera, microphone and PC,” Harbst observes. “[Sometimes], the cable will have to go pretty far.” He continues, “So, some are switching to fiber instead of copper, which is driving up the cost out of necessity. There are USB extenders, but, with three and four, they’re very expensive.” Cable length limitations, thus, remain a big deal. “It is very limited on distance at its core,” Harbst adds. “So, you can get into the extenders, but it comes with an additional cost.”

Poulin, meanwhile, turns back to the pandemic, saying that it forced us to adopt technology at a faster rate — in particular, videoconferencing technology. “The acronym BYOD — bring your own device — means you can do a presentation wirelessly,” he states.

“There was another term [known as] BYOM — bring your own meeting. And although a lot of people conflate the two terms, there is a distinction.” According to Poulin, these days, you can not only go into a space that’s equipped for it and do a presentation but also run a meeting remotely. “You can literally take over the room’s infrastructure, plug in your laptop and utilize the room’s cameras, speakers [and] microphones, onsite and remotely,” he declares. “That was a game changer.”

USB-C comes into the foreground here. According to Poulin, “Before, you’d have to plug in a bunch of things: a USB cable, a video cable, power to charge your laptop, etc. With USB-C, it’s all rolled into one. So, it gives you that capability. USB host switchers allow you to do these things.” He continues,

Tiers in USB topology

USB is a fairly easily repeatable signal, meaning it’s possible to take a USB hub with one connection and then split it out. As Harbst explains, “You can do multiple splitters, but, depending on the equipment, you can be limited in the number of repeatable tiers.”

“The subject of tiers in USB topology,” Poulin begins, “it’s the point where your USB system is going to stop working reliably. You can have up to seven tiers of USB, but then, after that, things like latency get in the way. On the eighth tier, you’ll run into some issues with your devices connecting reliably.”

He elaborates further, saying, “Most PCs would be the host of things. Generally, Windows PCs use one tier; a Mac might take up two. A USB hub can only have a max of four ports. So, if you have seven ports, it’s two USBs put together. If you use a Mac with a seven-port hub, that’s two tiers — and extension devices may or may not take up a tier.”

Poulin adds that it’s easy to get to that eighth tier without even realizing it. “Some computers, which generally host the USB system, may have multiple hosts within them,” he notes. “But you need to find out what it’s going to do and how many tiers it uses.” When a problem arises, it’s all too common for uncertainty to arise as to the cause. “From a support perspective,” Poulin continues, “when there’s an issue, we ask what’s in the signal chain, [and] then we work from beginning to end to figure out where the pain point is. Often, it’s because the user is over the seven-tier limit.”

A long, winding road

The long, winding road of USB standards has taken us this far — and the journey continues. As Harbst aptly points out, “It’s important for security and AV integrators to stay on top of [developments in USB] as they progress.” He shares an observation that’s inarguably true: People are always going to need greater data transfer speeds.