Chuck
No, sorry, I didn't, only the first few lines in which the author describes
the bridging of the 2 ports. Thanks (and to Piers) for enlightening me on the
existence of such protocols.
They sound like sensible restrictions, rather than sinister. And I now
remember that I had USB output to use in the car which did not charge a
previous iPhone: I was thoroughly confused by that, but no longer :-)
Chris
On 4 Jan 2013, at 23:10, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> I don't think you read my link. It discusses an *apparent* proprietary
> signaling system in 12V/USB chargers that iPads recognize and Androids
> do not. A high current charging device such as an iPad or Android
> tablet needs to be aware of the USB connection and, if it's attached to
> a computer, throttle itself back to the maximum current draw specified
> for a USB port on a computer (0.5 amp IIRC). However, if the charger is
> simply a USB connector connected to a 12V outlet in a car then the
> device can safely draw 2 amps or more. Certain of these 12V chargers
> will rapidly charge an iPad since the iPad somehow knows there's a high
> current capacity automobile on the other side of the USB connector. The
> Androids typically do not since they don't understand whatever the iPad
> is doing to realize it's charging from a car rather than your laptop.
> The recommended charger in the link is one that does allow an Android to
> draw 2 amps for charging... depending on which of the 2 USB sockets it's
> connected to.
>
> There's a lot of detailed engineering study in that link.
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