ToDo #212

USB power protocol

Added by Neels Hofmeyr over 7 years ago. Updated over 7 years ago.

Status:Neu Start date:11/17/2013
Priority:Normal Due date:
Assignee:Stefan Sperling % Done:

0%

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Description

find out what a USB device must do/be so that it is allowed to draw the full 500 mA of current from the USB bus.

History

#1 Updated by Neels Hofmeyr over 7 years ago

I think the usb-to-uart chip's datasheet has some mentions of this topic... (see Part List)

#2 Updated by Stefan Sperling over 7 years ago

Wikipedia has some general info: http://en.wikipedia.org/wiki/Usb#Power

#3 Updated by Stefan Sperling over 7 years ago

The "Standard Configuration Descriptor" contains a "bMaxPower" field which specifies the amount of power a USB device will draw from its upstream port (max 500mA). See "Universal Serial Bus
Specification, Revision 2.0", Section 9.6.3.
https://redmine.user.in-berlin.de/attachments/download/83/usb_20.pdf

#4 Updated by Neels Hofmeyr over 7 years ago

  • Assignee set to Stefan Sperling

A "descriptor" is discussed in AT32UC3C datasheet p. 883, and by UDESCA on p. 919 -- is that the one? can't find bMaxPower there, am still confused...

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