Mac Mini

[CRC]

On Sun, 4 Dec 2005 00:52:27 +0000, Dan Williams  
<williams.dan at gmail.com> wrote:

> I have a mobile that has a USB charger, but it will not charge unless
> the driver is installed. I don't know if the specs of USB mean it
> doesn't put voltage on a line unless it's told to.

A USB device is initially required to pull no more than one load (100  
ma) from the power bus. On initialization, the USB host queries the  
device to obtain the number of loads it requires (up to 5 - 500 ma)  
and determines whether it can provide that amount of power to the  
device. For devices requiring more than one load, the device is not  
allowed to pull more than the initial load until configured by software.

> I keep meaning to
> try it on a powered hub. But I don't have one.

 From the spec: "Hubs that obtain operating power externally (from  
the USB) must supply five unit loads to each port. Battery powered  
hubs may supply either one or five unit loads per port." So this  
should work independent of host initialization (if the hub follows  
the rules).

If the device is a standard device as defined by the specs, the host  
should initialize power independent of a driver. However, if you are  
on a M$ box, they don't always follow the rules even though they are  
a signatory on the spec...

	CRC