Integrating USB Into Products

By Allan Neville

January 1, 2007

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In recent years USB has taken the place of traditional serial standards as the main communications protocol between devices. Lately, there has been an increase in the market demand for products to support USB devices like keyboards, printers, and memories; or for products to communicate with a PC through the USB interface.

Since its introduction more than a decade ago, the Universal Serial Bus (USB) protocol has become a technology "rock star". Walk into any electronic store and most likely one out of three devices has a USB port.

It started as a substitute to old communications ports on the PC such as RS232 and the parallel port to meet the new demands of the PC market. And since then it has been used in everything from coffee mug warmers to 10GByte hard drives.

The USB specification defines everything from mechanical connectors and cables, all the way through operation of the system, network layers, and power management. We will review some of these issues in this article and look at some example implementations.

Brief History

The USB standard was officially introduced in 1995 by a consortium form by seven computer and telecommunication industry leaders: Compaq, DEC, IBM, Intel, Microsoft, NEC and Northern Telecom. Since then it has grown to more than 1000 members in the USB implementers forum (USB-IF).

In 1996 the USB 1.0 standard was released specifying the main aspects of the USB standard as we know it: support for 12Mbps high speed bus and a low speed bus at 1.5Mbps, the definition of the mechanical connectors, and the specification of the software stack.

By 1999 due to the popularity of the USB protocol and some problems that had been identified, revision 1.1 was released. This version clarified some ambiguities regarding timing and corrected some problems that existed in the previous revision.

But not until 1999, when Microsoft and Apple incorporated the use of USB into their operating systems did USB find "stardom".

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