USB gets set to go mobile

As mobile workforces grow, the capabilities of mobile devices have to grow as well. Cell phones, for instance, will soon feature more memory and storage space.

However, getting cell phones to share data is difficult. That could change now that USB On-The-Go, a standard which will supplement the universal serial bus (USB) 2.0 specification, has arrived. USB OTG is a wired solution to a wireless problem. The supplement allows users to port one wireless device to another, be it a cell phone, PDA, digital camera or notebook.

David Murray, a co-author of the original USB specification and vice-president of marketing for TransDimension in Irvine, Calif., said the USB specification was flawed in that it only allowed for one-way communication. Because the computer acts as a host to other “slave” peripherals, USB is driven by PC vendors and is, therefore, PC-centric Murray said.

“The PC had a lot of processing power and we took advantage of that,” he said. “We made the host complex. It allowed us to make the slave side inexpensive – they were just peripherals responding to requests form the host.”

The reason behind this, Murray said, was to ensure rapid adoption of the USB specification from the PS/2 port.

The problem is that USB does not let one PC talk to another as both are hosts, and USB only allows for one host and one slave. The same held true for mobile devices. Some devices would need to be able to take on both roles, and they needed a smaller connector than the ones used for PCs and their peripherals.

Terry Remple, co-chair of the On-The-Go workgroup, said he was working on a phone and said, “Let’s put a USB connector on,” when he learned it wasn’t standard on portable devices.

“Up until that point, whenever portable devices wanted to connect to a computer, people ended up using proprietary connectors,” said the staff engineer at San Diego-based Qualcomm.

He added that the cost for each proprietary cable – and companies could end up with hundreds of them – was US$30 to US$50, and that was a huge barrier to sharing information.

Remple started the workgroup and focusing on standardized connectors – small ones for peripherals and small ones for hosts, almost four years ago. It was then that he realized some devices were going to want to play both roles.

Today the USB OTG supplement has several variations: an “a” receptacle, a “b” receptacle, a “mini-ab” receptacle, a “mini-a” plug and a “mini-b” plug, so that devices can take whichever role they need to.

Both Remple and Murray agreed this type of fast sharing will help mobile workers.

“USB has become such a standard for PCs and peripherals that over time USB OTG will hit a lot of mobile workers,” Murray said. “Before they would have to set up a full PC to be able to send graphics, now they will be able to swap that easily.”

Remple noted Bluetooth will be good for small files and streaming data, but USB OTG will share large files quickly. Wireless devices will be able to share files over the supplement even if only one of them has the USB specification in them.

The supplement came out in September 2001 and silicon has been developed for it since then, according to Remple, but both he and Murray are not expecting to see USB OTG-enabled products until next fall.