[Engineering Feature]
USB Flexes Its Industrial Strength
Lean facilities in the industrial realm looking to make even quicker changes more simply may want to consider the improved USB standard.
EASY EXPANSION As in consumer products, USB is attractive because it greatly simplifies the addition of peripherals to a system. That’s very important in continously evolving industrial environments. Some of those products will become permanent parts of the design, and others will be attached only when it’s time to troubleshoot. In either instance, simplicity is a critical element.
“Once you have the USB port, you can add a hub and hang several devices off a single port without a huge software impact,” says Bohm. He notes that a few operating systems, though, don’t support the hub concept, so engineers need to explore that before using that solution.
However, products lacking full support are fading away rapidly. In many areas, the ability to add more connectivity is a central aspect of most designs. Consulting houses that work with a range of customers say multiport capabilities are now common.
“Two of the five USB-enabled designs we’re doing now have eight high-speed 2.0 USB host ports. Future designs will have up to 12 high-speed 2.0 host ports,” says Paul Nickelsberg, president of Orchid Technologies Engineering and Consulting.
But even in new designs, adding a number of ports isn’t always an option. In compact designs, there isn’t room for all of the connectivity that’s needed in products designed for use in a number of diverse industrial environments.
One alternative is StackableUSB, an enhanced version that increases I/O capabilities while adding ruggedization. It gives designers the benefit of USB’s broad availability and the ruggedization of PC/104, providing multiple channels of USB through a single connector. It supports up to 10 data channels and seven hubs on each USB channel.
Micro/Sys, which headed the creation of the specification, has unveiled more than a score of boards that let engineers link USB devices to a range of different CPUs. Samtec offers ruggedized connectors that tie stacked I/O boards together. Engineers can stack several boards together to add I/O while only creating a bit more height.
Though many systems being developed today include numerous ports, having just one or two connections isn’t a huge limitation. Several hubs can be linked together to add more ports. Latency may have to be accounted for when additional cables and hubs are incorporated, but that can be far more effective than replacing an installed product or redesigning one with limited I/O. Daisy-chaining often provides a large increase in connectivity.
“With a hub, you can cascade up to five levels, so you can add several ports to a chip that only has a single USB port,” says Steve Roux, senior strategic business development manager for NEC’s Digital Consumer & Connectivity Unit.
That sort of connectivity is most likely to occur in older systems. “Older systems” is a large category in industrial applications, where there’s often reluctance to replace any equipment that’s running without problems. A few of these products are so old that they’re still running DOS and using floppy disks. Replacing floppies with USB data storage can breathe new life into DOS-based applications.
“The most unique of our clients use USB in products that still run under MSDOS or DR-DOS environments. As floppy disk drives become obsolete, DOS-based products turn to USB for file system data storage,” Nickelsberg says.
Switching from a floppy to a USB thumb drive will significantly boost performance as well as convenience. But for many industrial applications, performance isn’t a major issue. The first version of USB, 1.1, will often suffice with its 12-Mbit/s data rate. Simplicity, ease of connectivity, and reliability are more important than bandwidth.
“USB 1.1 speeds are sufficient for most applications since the typical robot application does not require large file sizes, normally less than 1 to 2 Mbytes total,” says Dinsmoor.
Though USB 2.0 was finalized early in this decade and has become the de facto version in the broad market, chips compliant with the original version are still being sold. “USB 1.1 is still used for mice and keyboards,” says Bode. (For more on the latest version of USB, see “The USB 3.0 Speed Bump.” )
One drawback for industrial users is that many of the chips and other products are designed only to consumer requirements. That’s a problem in industrial facilities where broader temperature ranges are required. The availability of ruggedized products is expected to rise now that many automakers are integrating USB into vehicles to provide connectivity for MP3 players and other consumer products.
“There are a number of high-temperature solutions, and there will probably be more coming as the auto industry increases its use of USB,” says Mark Bode, vice president of connectivity marketing at SMSC.
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