Speed Up Industrial Video With The Right Connectivity Choices

FireWire is a great choice for high throughput over long distances, true isochronous peer-to-peer operation, and wide operating-system support.

Rod Barman,

Burke Henehan

ED Online ID #8044

Article Rating: Not Rated

DESIGN VIEW is the summary of the complete DESIGN SOLUTION contributed article, which begins on Page 2.

Greater computing power coupled with lower-cost, higher-pixel-count imaging sensors have fostered a new set of advanced industrial applications. These applications—such as vision systems, robotics, motion control, and wafer inspection/repair—make significant demands on the total computing system.

Aside from throughput, other key requirements for these applications include quality-of-service (QoS), connection distance, connection robustness, and data latency. Connection options include standard high-speed digital connections for Windows, Mac OS, and Linux machines: 100BaseT Ethernet, 1000BaseT Ethernet (GigE), IEEE-1394 (FireWire), i.Link, DTVLink, and SB1394.

Many of the industrial applications require high throughput or distances greater than five meters and can benefit from true isochronous, peer-to-peer operation with broadcast capability. On top of that, they need optical interconnects and top-notch operating-system support. For these, FireWire is an excellent choice.

FireWire has guaranteed, truly isochronous bandwidth allocated every 125 µs for data that can be termed "latency-critical." Each isochronous-capable node has its own 32-bit clock incrementing at 24.576 MHz (the cycle timer), which is updated to the cycle-master node's clock every 125 µs. The same packet that updates the node clock starts the isochronous "frame."

This article compares and contrasts FireWire's max cable length, optical implementations in harsh environments, broadcast write capability, and peer-to-peer communication with that of Ethernet and USB 2.0. In addition, a FireWire implementation used in Point Grey Research's 800-Mbit/s industrial camera is reviewed.

HIGHLIGHTS:
Total Throughput	The means of arbitration or deciding which node transmits next can significantly impact raw bit speed, as well as the coding of the data. For instance, FireWire's 1394b configuration has a raw throughput of 1 Gbit/s, but the data coding drops that rate down to 800 Mbits/s.
Connection Distance	IEEE 1394b extended FireWire's cable length by allowing more types of media. Specifically, it permits glass optic fiber (GOF) up to 100 m at any speed per cable connection.
Connection Robustness	If an industrial installation's cabling is in a dense electromagnetic-interference environment, optical connections might be preferred. GOF transceivers are too sensitive to EMI, though, so plastic optic fiber (POF) may be a good compromise.
Peer-To-Peer, True Isochronous Transport	FireWire allows peer-to-peer communication, meaning traffic may be sent directly to the node that requires data.
Broadcast Write Ability	FireWire features a broadcast write mechanism and address space. This is used for the cycle start message to update each node's cycle timer register (common time base).

Full article begins on Page 2.