USB-OTG

 

USB-OTG

From: http://www.usb.org

 

3.2 On-The-Go Device

In addition to being a fully compliant USB 2.0 peripheral, an On-The-Go device must include the following features and characteristics:

 a limited Host capability

 full-speed operation as a peripheral (high-speed optional)

 full-speed support as a host (low-speed and high-speed optional)

 Targeted Peripheral List

 Session Request Protocol

 Host Negotiation Protocol

 one, and only one connection: a Micro-AB receptacle.

 minimum IA_VBUS_OUT output on VBUS

 means for communicating messages to the user

 

 

3.6 Session Request Protocol

The Session Request Protocol (SRP) allows a B-device to request the A-device to turn on VBUS and start a session. This protocol allows the A-device, which may be battery powered, to conserve power byturning VBUS off when there is no bus activity while still providing a means for the B-device to initiate bus activity.

Any A-device, including a PC or laptop, is allowed to respond to SRP. Any B-device, including a standard USB peripheral, is allowed to initiate SRP. An On-The-Go device is required to be able toinitiate and respond to SRP.

 

 

3.7 Host Negotiation Protocol

The Host Negotiation Protocol (HNP) allows the Host function to be transferred between two directly connected On-The-Go devices and eliminates the need for a user to switch the cable connections inorder to allow a change in control of communications between the devices. HNP will typically be initiated in response to input from the user or an Application on the On-The-Go B-device. HNP may only be implemented through the Micro-AB receptacle on a device.