On Mon, 29 Dec 2008 09:22:28 +1100, Franc Zabkar
put finger to keyboard and composed:

I couldn't find anything in the abovementioned Wikipedia article that
discussed the 5th ID pin in relation to battery charging. AFAICS, this
pin should be floating at the phone end, not terminated with a
resistor to ground. Does the "Battery Charging Specification" redefine
the function of this pin, or is Motorola's implementation
non-standard?

This is the "Battery Charging Specification":
http://www.usb.org/developers/devcla...arging_1_0.zip

Fig 3-2 on page 13 shows a Dedicated Charger. The D+ and D- pins are
connected via a resistor, Rdchgr_dat, which has a maximum value of 200
ohms.

The ID pin is left floating at both ends.

Section 3.10 on page 16 defines a "Resistive Detection Mechanism"
whereby a portable device can differentiate between a dedicated
charger and a hub or host charger by looking for pullup and pull-down
resistors on D+ and D-.

In all cases the ID pin is floating.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.