Driver Support
One final piece of the puzzle is driver support. Ordinary PC hosts have lots of disk space to store drivers for a wide variety of peripheral devices which may be attached, and have floppy disk driver and/or CD drives, and perhaps an Internet connection, which makes it easy to install drivers for new peripherals as necessary.
Many handheld devices, however, have neither an easy means of installing new drivers, nor the space to store them. Storing several megabytes worth of drivers is a trivial task for a standard desktop or notebook PC, but even a few tens of kilobytes may be a prohibitive burden for some of the portable devices for which On-The-Go is designed.
To cope with this problem, the On-The-Go supplement requires that each dual-role device have a Targeted Peripheral List of supported peripheral devices. The Targeted Peripheral List is merely a list of device type, manufacturer, and model of devices that a particular dual-role device supports. Operation with any device other than those on the Targeted Peripheral List is neither guaranteed nor required.
An area for future work is the definition of "OTG Types". An OTG Type would be a specification, analogous to the USB Class specifications maintained by the USB-IF Device Working Group, which prescribes particular characteristics of a class of devices. The OTG Type specification would provide enough information that any dual-role device which supported that Type would be able to interoperate with any peripheral device which complies with the Type specification.
Current Status
The On-The-Go supplement completed its required industry review period and was released in final form on December 18, 2001. The supplement was developed by a committee made up of representatives from a cross-section of the industry. As such, it has a broad base of support from connector makers, IP vendors, silicon providers, software houses, and equipment manufacturers. From this broad base of support and committed involvement, it is anticipated that OTG devices will appear on the market shortly.
Now that the specification has been released, a major focus of the On-The-Go committee is education and evangelization. The committee has recently sponsored several industry training sessions in the U.S., Asia, and Europe. Such activities will likely continue in the future.
In addition, there are several areas for future work and companion specifications that are still in development. The On-The-Go Committee is developing a specification that will define the compliance testing needed to ensure that OTG devices meet the requirements of the specification. There is also considerable work to be done in defining OTG Types.
There is no better way to really understand the new features and correctly implement them in your own products than to get involved in working directly with the specifications and with the experts who designed them. To learn more about USB or to download the USB specification and ECN, visit http://www.usb.org/. To learn more about On-The-Go, download the On-The-Go supplement, read explanatory articles, learn about On-The-Go events, and join the On-The-Go committee mailing list, see http://www.usb.org/developers/onthgo/. Note that any company that wishes to access this information must be a registered member of the USB Implementers Forum.
The proliferation of powerful, high-capacity portable devices brings with it new problems in communications protocols. These problems are addressed by USB On-The-Go. The specification is available now, and ready to help enable the next generation of mobile computing.
<Biographies>
David Luke received his MSEE from Brigham Young University in 1993. He joined In-System Design (recently acquired by Cypress Semiconductor) in 1995. David serves as Chair of the USB-IF Mass Storage Class Working Group and attend at On-The-Go committee. He is currently working on the design of his seventh USB IC.
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