u*** otg协议规范

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u*** otg协议规范

 1.1 General
USB has become a popular interface for exchanging data between PC’s and peripherals. An increasing number of portable peripherals are using the USB interface to communicate with the PC. Many of these portable devices would benefit from being able to communicate to each other over the USB interface, yet certain aspects of USB make this difficult to achieve.
Specifically, USB communication can only take place between a host and a peripheral. However, in order to qualify as a PC host, a device must have several characteristics, including:
? storage for a large number of device drivers,
? the ability to source a large current, and
? a Series “A” host connector receptacle.
It is not practical for many portable devices to have all of the above characteristics, and in many cases, these characteristics are not needed in order to interface portable devices with each other.
In order to enable these limited-requirement, portable, USB applications, this supplement to the USB 2.0 specification was developed that allows a portable device to take on the role of a limited USB host, without the burden of supporting all the above functions of a PC.
1.2 Objective of the Supplement
The objective of this supplement is to define a minimal set of changes to the USB 2.0 specification [USB2.0], such that portable USB applications are enabled.
This is not a stand-alone document. It is a supplement to the USB 2.0 specification [USB2.0]. Any aspects of USB that are not specifically changed by this supplement are governed by the USB 2.0 specification.
1.3 Intended Audience
This specification is targeted to developers of PC peripherals and portable consumer electronic devices.

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