BY John Keller
The era of the widespread stand-alone input/output (I/O) board apparently is coming to an end, Embedded Computing industry experts say, as systems designers increasingly rely on mezzanine boards for the vast majority of their applications.
At the same time, the stand-alone I/O board still has utility for specialized applications, such as placing many different I/O schemes on a single board, or for handling blazingly fast, specialized I/O for the most demanding applications, such as radar processing, electronic warfare, and signals intelligence, experts say.
On the horizon for I/O lies the world of optical computing, which today designers implement primarily through the front panel of the Embedded Computing chassis, yet in the not-too-distant future, systems designers are likely to increase their use of fiber-optic I/O through the backplane with help from emerging standards, such as VITA 66.
"We see a lot more I/O these days going directly on the processing modules themselves, or implemented as mezzanine cards," says Anne Mascarin, solution marketing manager at Mercury Computer Systems in Chelmsford, Mass. "There is a lot of flexibility in I/O and where it resides. It really depends on the application."
I/O functionality that resides directly on single-board computers or as mezzanine cards plugged into these single-board computers can be implemented as specialized I/O matched to the application, or can be industry-standard I/O. "Most of our processing boards come with standard interfaces," Mascarin explains. "We are adding our GPIO line, which stands for General-Purpose I/O, which are discrete input/output lines but without a specific protocol. It is I/O wires and pins that the customer can define the protocol they want to run over it."
Although demand for standard I/O implemented on stand-alone boards appears to be winding down, I/O suppliers do field requests from systems integrators involved in upgrades and technology insertion who want to retain I/O on separate boards. "In some of the systems we have announced, our customers are still making 6U and 3U I/O boards, and we will include that in the system," Mascarin says.
"Our customers, and COTS companies like ourselves, are very much going away from I/O-based cards," says Steven Edwards, chief technology officer at Curtiss-Wright Controls Embedding Computing in Ashburn, Va. "The days of the 6U and the 3U data-acquisition card have gone by the wayside, and either the I/O is incorporated onto base cards that serve another function like a single-board computer, or primarily it is incorporated on mezzanine cards."
Ever-increasing bandwidth of I/O in high-performance Embedded Computing can make implementing I/O on mezzanine cards a challenge, but new standards are meeting many demands. The FMC card, which stands for FPGA mezzanine card, is designed specifically for field-programmable gate array architectures.
Some applications that call for the quickest possible I/O still call for specialized stand-alone boards. "You closely couple I/O to high-bandwidth processing to match requirements, but sometimes you step past what is possible with a mezzanine," explains Jeremy Banks, product marketing manager for SENSORS and I/O processing at the Curtiss-Wright Controls Embedded Computing office in High Wycombe, England.
"The very high ends of bandwidth, like 1 gigabyte per second, do hit a boundary where some I/O mezzanines can't cope with that and it calls for a stand-alone board," Banks says. "The key thing is to choose the right mezzanine for the given bandwidth."
Not all I/O mezzanines can meet all system requirements. North Atlantic Industries in Bohemia, N.Y., specializes in I/O boards that can handle many I/O schemes on one stand-alone board-most often either 6U or 3U VME or Compact PCI.
"Our philosophy has been multi- function I/O on boards; you can put as many as six different I/O functions on a single 6U VME board," explains Lino Massafra, vice president of sales and marketing at North Atlantic Industries.
Shipboard missile launchers are one example of multiple I/O on a board, Massafra explains. "Where you are monitoring a launcher, we monitor all kinds of A/D [analog-to-digital conversion] and discrete. We can monitor on a single board as many as 60 A/D channels or as many as 60 D/A channels."
Among North Atlantic's major talents is synchro resolver measurement, which keeps precise track of system movements, such as missile launchers or deck guns. "On a ship, we need to manage the position of a gun," Massafra explains. "The gun has left-and-right, and up-and-down movement. We can measure the position of that gun, and combine with a synchro that measures the movement of the ship, so the gun is always pointing in the right direction."
Looking to the future of I/O, optical computing and fiber-optics technology expected to play an important role. "Today, optical I/O is all front-panel based; that can be a challenge for things that are conduction-cooled or need two-level maintenance," says Curtiss-Wright's Edwards. "In the future, we'll see optical I/O on the base card directly."
VITA, the open-standards, open-markets trade organization in Fountain Hills, Ariz., is formulating the VITA 66 standard for fiber-optic I/O out the backplane. VITA 66 should be ratified sometime this year and, by the end of 2011, the market likely will see VITA 66 cards and backplanes.