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Re: USB-to-PS/2 adaptor: mouse works, keyboard doesn't

On Monday 2009 January 05 06:28:31 Emanoil Kotsev wrote:
> USB is powered when you attach the device. This means the usb device gets
> power over the bus after attaching it. I've read about power on/off with
> specific usb disks and devices. You may google about it.

That's not the whole story though.  According to the specification, power over 
USB is limited to 100mA until the both sides (host and device) negotiate, as 
which point it is limited to 500mA.  Unfortunately, some implementations have 
ignored this, and assume the other side will as well, expecting 500mA at all 

Linux is compliant with the specification.  Not *just* because "it's the 
standard" but because providing 500mA *could* physically damage devices that 
aren't expecting it.  Unfortunately, this can cause problems with (but not 
damage to) non-compliant devices when they only get 20% of the power they are 

Boyd Stephen Smith Jr.                     ,= ,-_-. =. 
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