The arrival of the USB 3.0 SuperSpeed standard has made a substantial contribution to supporting much higher data rates and the approach is now presenting a broad cross section of underserved industry sectors with the opportunity to implement higher performance video imaging systems. However, these systems remain very cost effective to deploy and do not call for the allocation of heavy engineering resources.
With a data rate almost an order of magnitude faster than the previous generation, USB 3.0 offers full backward compatibility, along with the same 'plug and play' ease of use that originally helped this standard to gain such universal appeal. In fact, it is estimated that there are more USB ports currently in operation worldwide than there are people.
USB 3.0 not only supports ultra fast data transfer – at rates of up to 5Gbit/s – but it also does so over distances of up to 10m. This is a major benefit as other interface technologies can often be very restricted in these applications, struggling to cope when there are more the a few meters of cabling involved.
Meanwhile, HD image quality is already becoming the norm for multimedia products located in the modern home. There is now also a plethora of applications found outside the confines of this domain, in which increased resolution, better contrast, greater colour depth and faster frame rates are all seen as being increasingly desirable. Among these are security, medical imaging and factory line inspection systems. Though greater prevalence of enhanced imaging technology in the near future seems a certainty, this will of course be reliant upon the introduction of advanced semiconductor technology in possession of far greater data transfer capabilities.
Furthermore, this approach to video imaging deployment allows the power delivery aspect of USB technology to be brought into play. Because USB 3.0 can deliver up to 900mA, many applications will only require one cable to be run between the camera and the data acquisition system, rather than one for video data and another for power. Clearly, this last point is likely to prove advantageous in remote video applications – such as for surveillance and industrial monitoring equipment – where the installation of multiple wires will be a notable drawback and ramp up the cost associated with deployment of the system. Figure 1 compares USB 3.0 with USB 2.0 and Camera Link interfaces, showing its credentials as the interface technology on which widespread proliferation of HD video implementation could be potentially based.
Figure 2 describes a straightforward set up, running on the Windows 8 operating system, where a high resolution microscope camera (2560 x 1440 pixels) is in the process of streaming imaging data to a HD display via USB 3.0. Data transfer takes place at a speed of 2.08Gbit/s, allowing a high resolution frame rate of 38frame/s can be maintained without any lag or image distortion being witnessed. In this way, there is no degradation of the viewing experience.
As well as delivering dramatically higher data rates than a system based upon USB 2.0 could muster, such a system can also benefit from the higher power levels that the USB 3.0 standard can maintain (900mA while still transferring data at full speed, as opposed to 480mA for USB 2.0).
The USB 3.0 data transfer functionality of the system that is detailed in fig 2 is provided by FTDI Chip's newly introduced FT601 SuperSpeed USB-to-FIFO bridge interface IC. The camera control and data capture functions of the system are both handled by the accompanying FPGA – in this particular case, a Xilinx Spartan 6 has been used. The FPGA holds all responsibility for the imaging system's timing functions – for example, taking care of setting the frame rate. From there, the acquired data is passed to the 32bit parallel data bus incorporated into the FT601 (this bridging device also features a 32bit FIFO data buffer RAM which can be made use of when required. The data is subsequently transferred to the PC across a USB 3.0 interface before being shown on the QHD display.
A single physical channel plus four multiplexed logical channels have been integrated into the FT601. In order to assure simplified implementation, the various internal sub-units of this IC are controlled by its hardwired processor. This is based on the proprietary 32bit core developed by FTDI Chip, which runs at a frequency of 100MHz. The multifaceted memory resource available to the FT601's processor core includes a 64kbyte on chip shadow program memory as well as 8kbyte of on chip data RAM.
Through the embedded microprocessing element, engineers are provided with a great deal of flexibility in how they can configure this USB 3.0 interface IC so that it will meet with their exact application criteria.
As many as 10 separate USB endpoints can be configured, which also provides more than ample scope with which to create composite devices when this is deemed necessary. The FT601 also comes with D2XX driver support, allowing it to be used with Windows, Linux and Mac operating systems.
Offering lower implementation costs than other data interface solutions and not being dependent on niche technologies that are less commonly understood by the design engineering community at large, the advent of USB 3.0 could open up a countless new possibilities for design engineers. This will enable the uptake of HD video in a far more diverse range of end applications than was previously imaginable – with the data transfer supported permitting respectable frame rates to be achieved without heavy investment in hardware needing to be mandated.
USB 3.1 still in development
Although USB 3.0 supports much faster data transfer rates than its predecessor, the USB community is looking to provide even faster data rates through USB 3.1. Whilst the specification was released on 31 July 2013, products featuring USB 3.1 interfaces have yet to reach the market.
According to USB.org, USB 3.1 will add a 10Gbit/s mode that uses more efficient data encoding and which should deliver more than twice the effective data throughput of existing USB 3.0 over enhanced … USB connectors and cables.
"The USB 3.1 specification primarily extends existing USB 3.0 protocol and hub operation for speed scaling along with defining the next higher physical layer speed as 10Gbit/s," said Brad Saunders, USB 3.0 Promoter Group Chairman. "The specification team worked hard to make sure that the changes made to support higher speeds were limited and remained consistent with existing USB 3.0 architecture to ease product development."
Gordon Lunn is global customer engineer support manager with FTDI Chip.
