Re: Stupid Apple hardware

On Sat, 11 Mar 2006 19:29:30 +0000, Rexx Magnus wrote
(in article <Xns9783C60DAEEABrexxdeansaund@xxxxxxxxxxx>):

On Sat, 11 Mar 2006 18:33:32 GMT, zoara scrawled:

The USB socket only has four connectors; two power and two data. Since
the iPod will charge over USB when connected to a USB port, that means
that the two power lines must be connected correctly in the cable. Since
the thing will sync that means the two data lines must be correct in the
cable. So what on earth is the iPod wall charger doing that stops it
charging other USB items? Sending power down the data lines, which the
cable (or iPod electronics) deals with?

Thanks to Gary for pointing this out - I was hoping to do something
similar and now know I can't. But I can't understand *how* it's doing
that, never mind *why*.

If the ipod charger is more than a mere set of wires - it will probably have
drivers that cause it to turn on and off.
I notice this with my pocketpc. The mac will happily charge it without
drivers - but plug it into a PC that doesn't have activesync/drivers on it,
and it'll power for about 10 seconds, then cut off as it's not a recognised
device, and therefore the PC deems it unnecessary to power it. Of course,
other devices that require power but no drivers (such as USB lights) have no
problem, as they're not detected when only connected to the power pins.



USB must be a managed bus, similar to a form of networking, since connected
devices have an identity- the mac or pc knows the identity of devices
connected to it, and hence must control whether power is released or not.

.

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