Embedded Considerations for USB On-The-Go

ABSTRACT

The On-the-Go (OTG) Supplement to the USB 2.0 Specification, published in December 2001, opens up a vast range of exciting new functionalities for USB-enabled devices. Traditionally, USB has maintained a rigid host-function network topology with multiple portable devices acting as slaves to the single PC master. USB OTG changes this paradigm with the ability for a function to act, often only temporarily, as a host. Instead of a strictly PC-centric environment, OTG devices can also communicate directly with existing function devices and even other OTG products. Along with opportunity, of course, come risk and complexity. So, what are the inevitable limitations to host functionality in an embedded (non-PC) device? What are the trade-offs that will have to be made in those devices in order to maximize battery life and minimize form factor? Exactly how PC-like should be expect our OTG devices to be and what are the design decisions that device manufacturers need to consider in order to meet the market's expectations?