Charging Neo Freerunner via USB port
shawn.t.rutledge at gmail.com
Fri Apr 18 23:18:45 CEST 2008
On Fri, Apr 18, 2008 at 1:44 PM, Flemming Richter Mikkelsen
<quatrox at gmail.com> wrote:
> If you make this kind of modification, there is no use in the autodetection.
What do you mean? Autodetecting that a computer is the host depends
on some digital communications rather than measuring a resistor.
There is no resistor between pin X and ground in that case, right?
> It is more safe to check for the 47k and the other values.
It would be safer but not as universal. Somebody will have to figure
out the tests for Samsung chargers etc. But probably every mini-USB
charger can supply at least 500mA, or if not, it would limit the
current itself. So I don't think there's anything very unsafe about
making that assumption. But we could show the actual battery charge
current on the mini-control panel which can be popped up by clicking
on the status bar, so if you need to know whether the phone is really
charging (rather than trying and not getting enough juice) you can
easily find out.
Anyway you are assuming no other charger in the world uses 47k, or
that if it does, it would be capable of supplying 1A, right? But, if
the phone tries to draw 1A and the dumb fast-charger cannot supply it,
then the current would probably be limited by the charger anyway. I
have a powered hub from which the Neo cannot even draw a full 500mA.
(Lousy hub, I guess, or lousy power supply that is powering it.)
Nothing gets damaged, but I was wondering why the phone wasn't getting
fully charged when plugged into that hub for days or weeks. Now I
have to use an actual motherboard USB port instead.
Moto also has some USB accessories like a headset, and a
headset-adapter. It will be interesting to see what happens when one
of those is plugged in; I suspect they used more resistor/transistor
tricks to detect those, too. Maybe they even abused the USB pins in
other ways to enable those accessories.
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