The USB spec continues its march forward

June 17, 2016 OpenSystems Media

Having spent far too much time wrestling with why, against statistical logic, I invariably only connect a USB connector successfully on the third attempt, the orientation agnostic USB Type-C connector is well overdue. That fact alone is enough to excite me, but the USB 3.1 revolution it brings with it leaves me figuratively panting.

Early USB 3.0 ports (now re-classified as USB 3.1 Gen 1) offered 5 Gbits/s (SuperSpeed) bandwidth, whilst USB 3.1 Gen 2 doubles this to a PCI Express-competing throughput of 10 Gbits/s (SuperSpeed+). Whether USB 3.1 now offers a complete alternative to PCIe will depend who you ask. For the vast majority, particularly those within embedded, the answer is yes, though avid PC gamers clutching the latest and greatest graphics cards will likely shake their heads.

In embedded, we’ve always loved the usability of USB but tend to implement it at track level on PCBs or using internal custom connectors that are more robust. We like to “fit and forget” and can’t risk external cables simply being pulled out, which USB 3.1 alone doesn’t resolve. However, watch this space for the USB Type-C secure connector that will facilitate a permanent fixture.

What’s more important in embedded is the ability to carry power, and lots of it. Historically, USB offered a relatively pitiful 2.5 W; it now provides a mammoth 100 W with USB PD. This wattage is enough to power the latest 1080P panel PCs twice, so it’s magnitudes more than your typical embedded device requires. Through a Type-C daisy chain, multiple local devices can also be powered from the same source! Or mobile devices can charge in a fraction of the time.

It’s not just power distribution that USB 3.1 over Type-C brings to the table, but also peripheral functions such as carrying display or Ethernet signals are also supported. This heralds a future of single-cable connectivity, a rationalisation trend started with PoE.

I’m as guilty as most when it comes to purchasing the cheapest available USB cables, some such poor quality that beyond not properly charging my smart phone, they’ve even caused the touchscreen to malfunction when connected. Rightly, the USB-IF recognises that to the layman, using cheap cables that don’t properly conform is a danger to the device itself, and the manufacturer’s brand, as inexperienced users won’t always attribute blame to the cable. Addressing this, USB Type-C authentication protects devices against damage from such cables and usefully facilitates device manufacturers providing GUI messages to that effect to the user.

Rory Dear, European Editor/Technical Contributor
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