5 May
2012
5 May
'12
3:58 p.m.
On Sat, May 05, 2012 at 06:52:21PM +0100, Pete Turnbull wrote:
On 05/05/2012 17:39, Alexander Schreiber wrote:
Actually there is sometimes a good reason. For example, an iPhone can
pull far more current than USB guarantees (well over an amp), so it
tests first. The proper charger has a couple of voltage dividers across
the power such that the data +/- lines are held at specific voltages
even at light load. If the voltage on each is within a specific (fairly
narrow) range the iPhone knows it can pull at least an amp. A different
range tells it 500mA. Else nothing.
Which is still wrong since you can pull up to 500 mA from a standard USB
port (after negotiation, but you probably can get away with trying to pull
500 mA regardless, especially if the other end is a stupid charger and not
a full USB host implementation - which shouldn't be too hard to figure out).
Kind regards,
Alex.
--
"Opportunity is missed by most people because it is dressed in overalls and
looks like work." -- Thomas A. Edison
On Sat, May 05, 2012 at 11:56:35AM -0400, Mouse
wrote:
The
connector is not all there is to it. I recently ran into a device
(not a phone, but it wouldn't surprise me if phones did the same thing)
that, if you plug in the wrong charger, even though the connector is
correct, displays a snarky message about how you have to use the
charger and cable that came with the device, and refuses to charge.
That is someone playing silly games. If you remember, name & shame
please