Stay connected with USB 3.1

Figure 1 - Survey result of VisionSystems DESIGN: Most popular camera type in two years.

USB as a camera interface has now become widely adopted and accepted by both, manufacturers and users of machine vision cameras.

4. USB 3.1

But, of course, development of the USB standard and technology did not end here. In July 2013, the usual suspects – Microsoft, Intel, Renesas etc. – finished the “Universal Serial Bus 3.1 Specification”.

So what was new with USB 3.1? The obvious answers seemed clear:

• it’s faster
• it has a new connector
• it allows for more power transfer

However, with USB 3.1 something changes: it does not necessarily introduce higher bandwidth. Unfortunately, things got a bit more complicated for USB users with the new revision number.

Connector

So what about the new connector? One can hardly read a technology magazine these days that does not feature one or several products with this new connector.

This connector is bound to become the ubiquitous and all-purpose single connector on PCs moving forward. In 2015 the Apple MacBook was shipped with only one single USB-C connector for powering the device, connecting accessories and displays. The current generation has four USB-C connectors, but again no other connector. Currently we see USB Type-C adoption on cables, smart phones, tablets, hard disks, monitors, docking stations, power adapters, notebooks, desktop PCs, USB thumb drives and so on.

USB Type-C is a really great connector, possibly the best connector specification ever made:

It’s small, fast, very versatile, higher power transfer – and the nicest thing about it: it’s reversible! Just imagine how much life time each of us wasted, rotating USB-A plug 3 times to find the correct orientation.

With a height of only 2.5 mm and a width of just over 8 mm, it is smaller than the current Type-A or Micro-B connectors, which is great because it allows to build smaller devices.

Type-C features 24 pins, more than twice as many as any previous USB connector, although not all of them have to be used on every cable. These pins include USB 2.0 and SuperSpeed data buses, power and ground, and the communication channel for PD protocol negotiation.

What is also new with USB Type-C? The USB host-to-device relationship is now accomplished through a “Configuration Channel (CC) controller” chip within the plugs and receptacles. A Type-C cable assembly using this chip embedded in one or both plugs is a “smart” cable, which is typically referred to as electronically marked cable assembly (EMCA). These cables can report cable characteristics to Type-C ports on hosts and devices, such as its current-carrying capability, performance, and vendor identification (USB Type-C Cable ID function). Considering that these cables can carry up to 100 W of power, it is especially important that they correctly report their electrical capabilities. All full-featured USB Type-C cables have to be electronically marked.

When you buy a USB Type-C camera make sure to get good quality cables from a trusted supplier, ideally the camera manufacturer itself.

Power Delivery

So let’s look at the third feature that is commonly associated with USB 3.1: higher power delivery. USB Power Delivery also is not a new feature, the standard was first introduced in 2013 with a modest power transfer of 7.5 W in order to charge batteries via USB. Since then, the PD standard has been constantly expanded and improved, with the most recent specification 3.0 having been released just this March. The current power delivery specification allows power transfer of up to 20 V and 5 A, or 100 W, depending on the device and host capabilities. This is a lot of power and will suffice for many applications – although, unfortunately, it is not enough to charge electric cars… yet.

Power Delivery is not mandatory for Type-C connectors. Basically it is possible to use the type C connector with devices that do not support the power delivery protocol. However, only the power delivery protocol allows for independent data and power role swaps for ultimate flexibility. PD allows for a monitor powering a computer which in turn powers the camera. Those roles of the individual devices can be swapped seamlessly even during operation, for example in case one device runs out of power or gets disconnected from power.

Power delivery supports Dual Role, which means it can work in both directions so the host can power a device, or the other way round, or both the computer and the camera can be powered through a display, and so on.

Figure 3 - Data output rates of 4 current generation CMOS sensors, which would benefit from higher USB 3.1 Gen 2 transfer rate.

The upcoming doubling of the transfer rate to SuperSpeed 10 Gbps and the data payload of almost 1 GByte/s will not only allow for very fast sensors, but also data output in RGB formats and bit depths of more than 8 bits per channel become possible.

The obvious benefits of USB 3.1, the Type-C connector and power delivery offer great potential for your camera application. But another important question for machine vision customers is: “What about cable length?”

Basically nothing has changed in this regard over previous USB implementations, at least not for 5 Gbps speed. A common misconception is that cable length is limited by the USB specification. It is not. In fact the specification explicitly states that it does not specify cable length. It does however specify electric parameters such as voltage drop, signal rise time, resistance etc. It also lists cable lengths that will typically be achieved with common cable material. However, when using high quality material and assembly, there is no restriction on cable lengths.

Obviously, with USB 3.1 Gen 2 speed it will be a more challenging for cable manufacturers to ensure that all the parameters are met for long cables. Possibly there will be shorter cables with 1 or 2 m initially for 10 Gbps signaling.

For the USB 3.0 Micro-B cables, passive cables up to 5 or 8 m are available. With USB 3.1 and USB Type-C IDS currently sees cables with 3 m length but expect longer cables to become available soon.

Another benefit of Type-C for the implementation of longer cables or fiber optic cables (up to 100 m) is to use active EMCA’s with additional electronics to provide signal conditioning by adding a re-driver on the data path. Active cables that report their configuration or use signal conditioning are referred to as “managed active cables”.

With more wires for the additional signals (full featured cable with Type-C plug on both sides), the cables get a bit larger in diameter. Cables are available with both, Type-C to Type-C (full featured) and Type-C to Type-A plugs (for pure data connections).

Ok. But is Type-C really suitable for industrial applications? Yes. USB Type-C cables are available with lockable connectors and even hi flex drag chain versions for small scale robotics.

In March of this year, the USB IF Device Working Group published the USB Type C Locking Connector Specification.

6. Summary

So we have several new terms and specifications here:

• USB 3.1 Gen 1 and USB 3.1 Gen 2
• Type-C connector
• Power Delivery.

The USB implementer’s forum’s idea is for manufacturers to clearly advertise the performance, power and connector capabilities of each device separately. Now, taking all of these together, a camera featuring all of the currently available technology would have to be called:

USB 3.1 Gen 1 camera with Type-C™ connector and Power Delivery

USB SuperSpeed cameras are used in a large number of applications already and continue to win an increasing share of new machine vision design-ins. Users that need high performance cameras should first consider USB 3.1 products before turning to bulky, power-hungry and comparably expensive solutions with high speed interfaces and frame grabbers.

When considering USB 3.1 Gen 1 cameras, switching to an USB Type-C model now, will offer an absolutely seamless transition to twice the data rate in a couple of years – and USB 3.1 cameras with Type-C connectors do offer many great features that you will benefit from right away:

• Very high data rates of more than 400 MB/s
• The best cost-to-data-rate ratio of any camera interface available
• Super compact connectors that are lockable, versatile, and reversible.
• Power delivery for supplying sufficient power to your device allows you to eliminate cabling, saving cost and time.
• Of course, USB 3.1 Gen 1 and Gen 2 are fully USB 3 Vision compatible
• USB 3.1 offers so many possibilities for connecting almost any kind of device that it will become the single ubiquitous digital interface.

Cameras which combine all these benefits are already available. In late summer of 2016, IDS introduced several new models featuring USB 3.1 Gen 1, the great new type C connector, and hardware support for 12 W power delivery.

So don’t wait any longer. Taste the future. “Stay connected with USB 3.1”