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Fiberbyte's modules give synchronous realtime control on USB

Posted: 17 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:fiberbyte? usb? usb-insync topology? daq-2500x?

Module features realtime I/OAs you can garner from Fiberbyte's detailed and exhaustive press release, this is an unusual and relevant product for deterministic applications. Not said is that the USB-inSync topology is comprised of distributed I/O and hi-density stacking multi-function modules that let you synchronously control, trigger, and sample, using multiple modules on a single USB port. These modules are also DIN-rail mountable.

Also not mentioned in the company's press statement is the fact that a USB-inSync system is designed to run under Windows. Your host PC will need to run Windows 2000 or Windows XP, and have a Pentium III processor, or better. You'll need at least 128MB of RAM and about 10 megs of spare hard disk space, too. And, your PC will need a USB v1.1 (or higher) host controller.

DAQ-2500X module
The DAQ-2500X has four independent 16-bit resolution 100kS/s simultaneous-sampling analog input channels. Each channel packs its own A/D (analog-to-digital) converter.

The module's big FIFO enables burst data sampling for a second of data, with all four A/Ds sampling at 100kS/s. Together, you get 1MBps data throughput. The module also supports programmable digital I/O and triggering.

Especially significant is the realtime I/O. That's just the ticket for distributed test environments that are revamped as lab needs change. Without USB-inSync, you're stuck with conventional USB.

Remember, USB was designed to concurrently operate multiple devices that vary in function. To accomplish this, USB is an asynchronous bus with multiple devices sequentially interacting with a PC. That very async operation prevents peripherals from interacting with each other in a deterministic way. USB has a limited capacity to synchronize events or processes from multiple devices.

Phase-locked clocks
In contrast, the USB-inSync DAQ-2500X has its own local clock that's phase-locked to that of every other USB-inSync device on a PC's USB network. A master hub operates as a timing controller to sync all the device clocks, regardless of the number of standard USB expansion hubs used. The master determines any phase offset and provides a correction factor to each USB-inSync device, to ensure all operate synchronously.

This syncing process also occurs automatically during USB device enumeration, and is repeated each time a new USB device is plugged in. As soon as Windows recognizes a device, it's available for synchronous operation.

The syncing process

The scheme also provides deterministic triggering. Processes and tests can be started and stopped in a very controlled manner.

Automatic sync

Unlike most USB data-acq modules, USB-inSync devices also automatically sync over standard USB expansion hubs, as opposed to async USB devices that only support synchronization within one module, and where synchronous channel expansion is only possible if you buy a bigger data-acq module. With this system, you can scale deterministic channel sampling by expanding to multiple USB devices with off-the-shelf USB hubs.

As in any test suite, price, speed, and resolution are key. Also, as I noted, most high-end test systems rapidly acquire lots of data. That's due to today's systems with high channel counts, faster sampling rates, and ever higher resolution requirements.

Embedded platforms and realtime expansion backplanes are usually needed to accommodate those concomitant demands. Many of these are PXI, CompactPCI, VME or VXI-based. Nonetheless, even with high performance platforms, critical test data that can take only seconds to acquire on the test system itself can take minutes to transfer to a PC for storage, analysis, or control.

That's where the USB-inSync comes in, establishing PC control that eliminates data transfer and formatting problems, while reducing overall test times, and therefore, cost. The result is better test efficiency.

Also, as opposed to PC-compatible devices that only provide interfaces for batch data upload, this PC control scheme continuously enables both upload and download between a test device and a host PC. You get simultaneous software control, data acquisition, and data storage.

Complements Ethernet
What about Ethernet and IEEE-488/GPIB? After all, Ethernet is capable of integrating multiple test devices with a PC, right?

Yes, but Ethernet has limited ability to sync test gear in realtime. It's better suited for linking multiple databases together for trend monitoring and for remote control and monitoring. As such, kudos is owed to Fiberbyte for developing this realtime USB-inSync platform to compliment Ethernet.

The USB-inSync platform can expand to 127 devices and hubs using the standard USB architecture. All the while it maintains multi-device synchronization, with standard USB hardware.

Compared with IEEE-488/GPIB, plug-and-play USB-inSync offers faster data transfers, too (up to 12Mbps), and ease expansion to many channels. As a USB peripheral, USB-inSync also supports hot-swap operation, and you don't have to open a PC's chassis to swap plug-in cards.

Test by cellphone
You can even use a USB-inSync system with a PDA (personal digital assistant) if it has a USB host controller port, and most do these days. If your PDA has a host controller (not a USB device port), you can set up a multi-channel test platform that's controlled via your handheld operating under Pocket PC software.

Data can then be piped directly into Outlook or Excel for subsequent transfer to your desktop PC. Imagine being able to run sophisticated test procedures in the field from your PDA/cellphone!

Legacy integration
Like most data-acq systems USB-inSync is modular, expandable, and customizable. Fiberbyte also designed its product to protect your existing investments. Most systems comprise unmatched hardware glued together by realtime software such as National Instruments's graphical LabVIEW environment. These types of stitched-together systems let you create sequenced test routines that integrate synchronization and automation.

That fact of life hasn't been lost on Fiberbyte. Its product comes with a LabVIEW driver so you can integrate it with other equipment (for production applications, most folks write their own software in VisualBASIC or C++). What's more, the system's distributed format is capable of operating test equipment up to 25m away from your PC controller.

Stay tuned
Although Australia-based Fiberbyte isn't a household name, the company has been actively involved for many years with product development and systems integration using its core USB-inSync technology. As its name implies, the company initially focused on fiber optics test equipment, but its core USB-inSync technology is now slated for more blanket data acquisition apps. Watch for developments from this firm.

- Alex Mendelsohn

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