[clug] A "mount" defeat - was Re: Persuading Debian to talk to an Android tablet via USB?
grail at goldweb.com.au
Thu Oct 21 05:37:32 MDT 2010
On 21 Oct 2010, at 21:48, Hal Ashburner wrote:
> I'd be thinking about a different SD reader before getting a whole new computer. Or a powered usb hub to plug the cheap nasty PoS you have into maybe. Definitely no need to update the whole machine to read an SD card.
For Felix: there are several different versions of USB - 1.0, 1.1, 2.0, and in each version there are "bus powered" and "self powered" devices. The theory is that a USB port controller is supposed to be able to negotiate with devices about whether to provide power, and if so, how much. The USB port is supposed to be able to supply up to 1.5A, and some high-power devices will request the "whole nine yards" - but some USB chipsets are only capable of delivering 1.0A or so between all their ports (being intended for servicing a mouse and a keyboard, and nothing else), leaving the power-hungry (and usually cheaper) USB devices starved (and thus non-functional).
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