FireWire: Blazing the Way for Industrial Vision

Contributed by:
Michael Gibbons, Product Marketing Manager
Point Grey Research Inc., Vancouver, BC, Canada

While there isn’t a single digital interface that works best for all vision applications, there is one that continues to lead the pack as the technology of choice for most industrial machine vision applications—and it’s not GigE Vision™. IEEE 1394 is the interface leader in an industry with substantial change in both technology and customer requirements. Greater computing power, an increase in availability of high quality megapixel image sensors, advances in FPGA design and electronics miniaturization, and an overall decrease in component costs are opening new opportunities in machine vision. Customers, meanwhile, want more pixels at faster frame rates, superior reliability, and a migration path for future retrofits.

Consider the following example: a machine vision system inspects bottle cap tamper bands, which are used by manufacturers to guarantee bottled product quality and freshness. The system is conveyer-based, and uses small analog “ice cube” cameras that are mounted within a custom enclosure and controlled by a desktop computer located 8 meters away. To acquire a 360-degree image of the object, while maintaining a high inspection rate, multiple cameras are placed around the object. Images are acquired at the same time using an external trigger, delivered with very low latency to the host system, and finally processed by third-party vision software. The manufacturer wishes to replace the analog cameras with digital cameras without changing the enclosure or additional cabling.

IEEE 1394 is ideally suited to this type of application. It supports high 80 MB/s data rates, works seamlessly with multiple cameras, and lends itself well to the transmission of real-time data. FireWire has guaranteed, truly isochronous bandwidth that is allocated every 125 µs for data that can be termed "latency-critical." This allows for low-latency data distribution and enables the latency of that data to be deterministic. It does not suffer from some of the quality of service (QoS) issues that are inherent with some other interfaces, like Gigabit Ethernet, which relies for its operation on collision detection and tends to produce more CPU loading than IEEE 1394.

In the majority of cases, the host computer system is located within the 4.5-meter maximum distance that is recommended for IEEE 1394 cables. Several high performance and cost-effective options are available where this is not the case. These include hubs and repeaters, and cables that are longer than 4.5 m and still meet the FireWire electrical requirements. Other unique options are also becoming available, including the FirePRO™ LDR (Long Distance Repeater) from Point Grey Research, which can transmit and receive IEEE 1394b 800 Mb/s data over 100 meters of standard Cat5e cable using an off-the-shelf GigE physical layer.

IEEE 1394 supports a common Instrumentation & Industrial Digital Camera (IIDC) camera control standard, which is critical when building or buying vision software. Any IIDC-compliant camera can be used with any vision software package that also supports IIDC, like those from Cognex®, National Instruments®, Matrox®, and MVTec™. FireWire also allows for much smaller camera designs, like those of many analog cameras, and a single cable can provide both power and data. This maximizes ease-of-use and reliability of the system. New advances in FireWire technology will allow doubling the bandwidth up to 160 MB/s without any change to the cables or connectors, making it easy to integrate higher data rate cameras in the future.

Selecting the right interface at the start can save a significant amount of time, resources and money, both during initial application development and for future projects. Of the digital interfaces, IEEE 1394 is the best suited for most industrial machine vision applications. It offers high data rates with guaranteed bandwidth and low latency, excellent reliability, power and data over a single cable, and a common camera control standard.

Michael Gibbons, Product Marketing Manager
Point Grey Research Inc., Vancouver, BC, Canada