High Definition camera deployment using superspeed USB interconnect technology

High definition (HD) video offers improved picture quality, greater colour depth, increased frame rates and superior contrast over traditional video technology. It has, as a result already seen widespread adoption in home entertainment applications - effectively becoming almost ubiquitous here. There are however a vast array of other places where its employment could prove to be advantageous in the future. The following article will look at how the advent of the USB 3.0 interface could open up new opportunities for HD video implementation.

Some of the sectors that could majorly benefit from HD video implementation include factory automation, surveillance and healthcare. All of these are likely to require the rapid identification of objects, and are therefore in need of a combination of high frames rates and strong image clarity. The envisaged video imaging systems serving these sectors must however still maintain a high degree of cost effectiveness too. USB 3.0 (SuperSpeed) has characteristics that make it very attractive for such implementations. In addition to supporting ultra-fast data transfer, it is also capable of doing so over distances of 10 metres (while other interface technologies are often limited just a few metres). Implementation of video imaging hardware via this method also makes use of the power delivery element that USB technology bestows. This eliminates the need for separate cable feeds for power and data - thereby lowering the overall deployment cost, as well as saving space.

USB ports first became popular during the mid-1990s. At that stage these were merely a means by which low data rate connectivity could be delivered to peripherals (such as mice, keyboards, printers, etc.). Since then USB has continued to progress, and today there are estimated to be in the region of 7 billion ports in operation globally. The USB 3.0, though originally ratified back in late 2008, is now starting to feature in electronic system designs. Global Industry Analysts has predicted that worldwide annual sales of USB 3.0 enabled devices will ramp up quickly reaching the 3 billion units mark by 2018. The impetus behind this will of course be to meet demands for higher speed data transmission between electronics hardware - in particular transmission of video material. USB 3.0 pushes the performance envelope significantly - boosting the data speeds that can supported by an order of magnitude compared with the previous USB incarnation (USB 2.0), as well as bringing other functional benefits. Nevertheless it offers the same plug-and-play functionality that engineers have come to expect. Figure 1 compares USB 3.0 with USB 2.0 and Camera Link interfaces. It details how this latest interface technology allows the bottlenecks that have previously been experienced when transferring video content to be removed completely.

Proliferation of HD video technology will call for a new generation of interface ICs. Figure 2 describes an imaging system utilising USB 3.0. Running on the Windows 8 operating system, it incorporates a high resolution microscope camera (2560 x 1440 pixels) from which imaging data is streamed to a QHD monitor via a USB 3.0 interface. The data transfer speed of 2.08Gbit/s means that a full resolution frame rate of 38fps can be sustained without any lag or image distortion occurring. As well as enabling consistently higher data rates than a USB 2.0 solution could deliver, this system can also benefit from the elevated power levels supported by the USB 3.0 specification - 900mA while still transferring data at top speed (compared with 480mA for USB 2.0).

The high data transfer capacity of the system described here stems from FTDI Chip’s new FT601Q SuperSpeed USB-to-FIFO bridge interface IC. The camera control and data capture functions of the system are both handled by the accompanying FPGA device (a Xilinx Spartan 6 is used in this example). The FPGA takes care of the imaging system’s timing functions (such as setting the frame rate, etc.). From there the acquired data is passed to the 32-bit parallel data bus incorporated into the FT601Q and subsequently transferred to the PC over the USB 3.0 interface before being displayed on the monitor.

Summary of items making up video imaging design example:

  • Toshiba 2560 x 1440 pixel resolution microscope camera
  • FTDI Chip FT601Q SuperSpeed USB-to-FIFO bridging IC
  • Spartan 6 FPGA from Xilinx
  • PC (incorporating a USB 3.0 port)
  • QHD Monitor

Summary of FT601Q from FTDI Chip:

  • 3.0 SuperSpeed USB-to-FIFO bridge
  • Integrated 32-bit FIFO bus
  • Hardwired microprocessor with proprietary 32-bit core running at 100MHz
  • Supports USB bulk transfers
  • 1 physical channel & 4 multiplexed logical channels
  • 16kByte Tx & 16kByte Rx endpoint buffers
  • Configurable 16kBytes FIFO buffer
  • Can configure up to 10 separate USB endpoints
  • Offered in QFN-56 and QFN-76 packages
  • D2XX drivers for Windows, Linux & Mac platforms (with optimised data structures for performance/efficiency)
  • Supports power management, suspend & remote wakeup

A single physical channel plus 4 multiplexed logical channels have been integrated into the FT601Q. Two modes of operation are provided. The first is a 245 synchronous FIFO legacy mode similar to that seen in earlier FT232H devices but with a 32-bit interface. The second is an enhanced FT600 FIFO mode catering for 4 discrete channels. The separate logic channels have 8-bits lengths, with each allowing for a full-32 bit interface to be created, but supporting asymmetric transfers. So that simplified implementation is assured, the various internal sub-units of the interface IC are controlled by its hardwired processor. This is based on the proprietary FTDI Chip 32-bit core, which runs at 100MHz. The multifaceted memory resource available to this core includes a 64kByte on-chip shadow program memory as well as 8kBytes of on-chip data RAM.

Through the embedded microprocessor resource of the FT601Q, engineers are presented with the design flexibility they need for configuring this USB 3.0 solution so that it matches their particular application requirements. Up to 10 separate USB endpoints can be configured, so that more than sufficient headroom is made available to engineers to create composite devices if needed. A completely new driver architecture has been developed to support designs where there are 8 or more data endpoints involved. It is optimised to extract full performance from the system whilst maintaining FTDI Chip’s standard D2xx API. This driver support permits the device to be used with Windows, Linux and Mac operating systems.

USB 3.0 could prove to be the catalyst that leads to large scale uptake of HD video in non-consumer applications. It enables a dramatic reduction in implementation costs when compared to other data interface solutions, as well as avoiding heavy investment of engineering resources. Furthermore it means system designs are not dependent on niche technologies that are less commonly understood by engineers. Through utilisation of USB 3.0 the higher frame rates and crisper images desired for modern system implementations can be achieved without major financial outlay in the associated electronics hardware or allocation of large amounts of time and effort.