USB on-the-go goes for peer-to-peer connectivity

Computer Technology Review, May, 2003 by Joshua Piven

By one estimate, the Universal Serial Bus (USB) interface can now be found in more than one billion products. Since its inception at Intel and Microsoft hardware "plugfests" in the early 1990s, USB has--in short order--come to dominate the market for computer peripherals that use an external connection to a PC.

Now, USB is poised to greatly expand its realm and move into the highly lucrative-and highly competitive--consumer electronics market, a market currently dominated by IEEE 1394, also called FireWire. While USB 2.0 brings near-half gigabit throughput levels, like its predecessor it has been hampered by its original design: An interface with a PC at its center. With no peer-to-peer connectivity, USB alone is not appropriate for today's technology universe, where various types of devices communicate with one another, without a computer.

Good To Go

USB On-The-Go (OTG) was introduced in 2001 to address this limitation (for a full discussion see the March, 2002 issue of CTR, available at wwpi.com). After almost 18 months of design and development work, new devices with OTG are about to hit the market, and from some of the industry's biggest names.

A supplement to USB 2.0, OTG supports device-to-device connectivity (known as "peering" or "ad hoc networking") and adds the following enhancements to a typical USB device: limited host capability to communicate with other USB devices without the need for PC intervention; a small USB form factor for highly mobile devices; and low power operation to preserve battery life. (An external OTG chip uses about 20-30 miliamps, and about 8 miliamps at the port.)

A device with such features is known as a "dual-role" device and can act as either a host or a peripheral when connected to other devices. Unlike a USB 2.0-compliant PC, a dual-role OTG device need not have the capability to identify any other USB device. However, any such dual-role device must be able to operate as a standard-compliant peripheral when connected to a PC.

In a major vote of confidence for the new connectivity option, Motorola has announced that it has licensed OTG technology from TransDimension, and will add it to chips in a number of forthcoming devices, including phones and PDAs.

In a sign of the increasing importance of peer-to-peer device connectivity--and particularly in mobile phones--Motorola's announcement follows a similar licensing agreement between TransDimension and Qualcomm, the world's largest maker of CDMA chip sets. TransDimension's OTG technology will be included in Qualcomm's MSM6500 chipset, which provides roaming between CDMA and GSM networks.

Driver's Ed

How will devices with embedded OTG be different from existing devices without it? One of OTG's most compelling features is that it vastly reduces the software complexity that is part and parcel of designing and adding a new piece of hardware to another device. USB OTG groups devices in one of several categories (or classes): audio, communications, human input, video, imaging, and mass storage. Any device that includes a driver for a specific class can communicate with any device in that class, obviating the need for device-specific drivers (the connection is made via a mini- or full-size connector, depending on the device).

Further, new devices with OTG will even be able to peer with existing, non-OTG USB devices--provided the manufacturer of the new device supports older hardware.

But perhaps the most important indication of the vast potential for OTG can be found in a recent announcement from SoftConnex Technologies Inc., a maker of OTG host software. SoftConnex has joined the Symbian Platinum Partner Program and has released its USBLink Host software solution for the Symbian OS. (TransDimension bought SoftConnex in December of 2001, but the company continues to operate independently, effectively functioning as the software arm of TransDimension.)

As a result of SoftConnex's participation in the Symbian program, mobile phone manufacturers that standardize on the Symbian OS will have access to the company's USBLink Host.

By integrating the USBLink Host into Symbian-based phones and communicators, SoftConnex says, OEMs can connect various internal components such as Bluetooth modules and mass storage devices for memory media interfaces, as well as enable external connectivity to any USB-enabled peripheral device, such as a printer, PDA or digital camera.

From the standpoint of integrating USB with mobile phones, how important is the agreement between Symbian and SoftConnex? According to some observers, Symbian will rule 3G phones. "Last year alone there were over 2 million mobile phones shipped running the Symbian operating system," says John Strand of Strand Consult, a wireless market watcher in the U.K. "These phones came from three different manufacturers, manufacturing 13 different models running Symbian. With 22 new mobile terminals in development from 8 manufacturers, Symbian will be the operating system for a huge percentage of the high-end and medium-range mobile phones in the coming years--aiming at 35 to 40 percent of the total mobile phones shipped in 2004."