Test & Measurement World, July/August 2012

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MACHINE VISION USB 3.0 making headway into cameras USB 3.0 doesn't just let you download movies or transfer files faster than previous versions, it also improves industrial camera speeds. The USB3 Vision standard will let cameras, computers, and software interoperate as well. BY PAUL KOZIK, POINT GREY RESEARCH U SB 3.0, once known as Superspeed USB, offers considerable perfor- mance improvements over USB 2.0, answer- ing the demand for a high-speed, high-bandwidth computer peripheral bus. Consumers who down- load large files such as movies and e- books can use USB 3.0 to provide the high bandwidth they need for fast data transfers. Engineers looking to rapidly transfer images from industrial cameras can also benefit from USB 3.0, and several manufac- turers of industrial cameras have released entire product lines of USB 3.0-based cam- eras to meet this need. Unlike consumers who download data to memory de- vices such as hard drives and flash drives, engineers need application software and a pro- gramming interface to transfer images from a machine-vision camera to a host computer. In response, the AIA (Automated Imaging Association) is devel- oping the USB3 Vision camera inter- face standard, which will enable in- teroperability among a variety of imaging components. This standard, combined with the advanced capabili- ties that USB 3.0 offers, makes USB 3.0 a viable option for engineers who are developing machine-vision systems. Best in class Like other digital interfaces, USB 3.0 provides high data-transfer rates over a single cable, which simplifies its use and makes it cost-effective. In fact, USB 3.0-based vision systems are competi- tive with systems based on other inter- faces. It can outperform many of them in terms of bandwidth and low CPU usage (see Table 1). USB 3.0 enables DMA (direct-memory access) data transfers, which allow images from the camera to pass directly to host memory without CPU interrupts. That greatly reduces CPU usage during data trans- fers and frees resources for image-processing applica- tions. USB 3.0 cables improve FIGURE 1. A USB 3.0 cable adds five wires to the USB 2.0 interface. USB 3.0 uses both parts of the USB connector while USB 2.0 uses the left side only. Test & Measurement World | JULY/AUGUST 2012 | –28– upon the half-duplex com- munication offered by USB 2.0 cables, where data flows in only one direction at a time. USB 3.0 cables add five wires for a total of nine wires in the connectors, and the cables use a dual-simplex in- terface that lets data flow in two directions at the same time. USB 3.0 cables are backward-compatible with USB 2.0, however, so users

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