On 4/5/2013 10:45 PM, Francis C. wrote:

To my knowledge, I don't have any "motorola charging software" on my
Linux laptop - but I just plugged in a standard mini-USB cable (USB 2.0
on one end, mini-USB on the other) and it charged the Motorola RAZR V3.

I suspect that Linux includes the Motorola USB drivers that enable
charging from a USB port. Windows doesn't.

Then I took the exact same setup, and plugged it into a wall-wart USB
charger, and it failed. Likewise with the cigarette lighter USB charger
in my car.

Clearly this cable does NOT have the resistor (it's a generic USB cable),
and I don't know that motorola phone tools was ever installed. Looking
on my system (using updatedb) I see there are "some" files with the
word "motorola" in them, e.g.,
/usr/src/kernels/2.6.32-279.1.1.el6.x86_64/include/config/usb/serial/
motorola.h

That looks like the Motorola USB driver.

You could sacrifice an old Motorola car charger or home charger to get
half of the proper 5 pin Mini USB cable and solder it to a USB A cable
and put in the resistor. Or buy the appropriate cable.

BTW, on my Google Nexus tablet, it won't charge from a standard USB
cable connected to a USB charger. I have to short the USB data pins to
get it to charge.

The reason Motorola and Asus and other manufacturers do this sort of
thing is not just to be annoying and to sell more of their own chargers.
The device needs to know how much current the charger can provide. A USB
port needs to provide 500mA but the reality is that many USB chargers
can provide much more the minimum, and even many computer USB ports can
provide much more than the minimum. The device can charge at a higher
rate if it knows the charger can provide higher current.

"According to the spec sheet for the Enhanced Mini USB interface
circuit, shorting pin 2 to pin 3 (the data lines) and putting a resistor
of 200kOhm on the ID pin x to pin GND will put the phone into Dumb
Mid-Rate Charger (500mA) mode with 1.225 volts on pin x. Putting a
440kOhm resistor on pin x to pin GND will put the phone into Dumb Fast
Charger (1.25A) mode with 1.68 volts on pin x."