Charging Neo Freerunner via USB port

Alexey Feldgendler alexey at
Fri Apr 18 22:45:44 CEST 2008

On Fri, 18 Apr 2008 21:06:26 +0200, Michael Shiloh <michael at>  

>>    * you mention 'other manufacturers' that 'identify their own  
>> chargers' with various resistors... if I have one of those chargers,
>> is there a way to get the phone to ID it?

> There are two issues here: First of all, you have to know the value and  
> location (i.e. between which two pins) of the resistor. There is no  
> standard, no gathering place of all this information. You can search the  
> Internet in case someone has posted this.
> I'm not sure how we measure the resistor. My guess is we measure the  
> current and deduce from this. Measuring the current requires an analog  
> to digital converter (ADC), which we must have wired up to the pin in  
> question. If an arbitrary charger uses a different pin, and if we don't  
> have an ADC on that pin, we won't be able to detect the resistor there.
> That said, the most common location for a resistor is the same as ours,  
> so you're in good shape.
> Next, you have to modify the code to do this. Trivial for all you  
> developers.

This could actually be done by an application downloadable by a user who  
knows what he's doing. The user starts the application, plugs in the  
charger, the application measures the resistance. If it's not something  
identifiable, too bad. Otherwise, the user reads the output current  
specification on the charger and adds the pair (ID resistance, current) to  
the table.

> The reason I think this is of limited use is that I would guess that  
> most of you will simply read the label on the charger, and then use a  
> utility to override all the automatic detection and simply tell the  
> charging logic that 500mA or 1A is available. Automating this is a lot  
> of work for little gain.

Not so little if you have a particular charger (say, Motorola) and use it  
to charge Neo every time. You'd really want it to auto-detect the charger  
instead of choosing the charging current manually every time.

Alexey Feldgendler <alexey at>
[ICQ: 115226275]

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