To charge an iPhone, 3G, 3GS, 4 / iPod Touch, 2nd gen, 3rd, 4th or Ipod Classic (6th Gen),
usb data- (25) should be at 2.8v, usb data+(27) should be at 2.0v. This can be done with a few simple resistors: 33k to +5v (23) and 22k to gnd(16) to obtain 2v and 33k to +5v and 47k to gnd to obtain 2.8v. This is a notification to the iphone that it is connected to the external charger and may drain amps from the usb.
iPOD nano 充電関連部分は次のようになってました。
Pin23: 5VDC(+) > USB Power 5 VDC (+)
Pin25: Data (-) > USB Data (-)
Pin27: Data(+) > USB Data (+)
Pins 25 and 27 may be used in different manner. ing, up to 1A, see below.
To charge iPod Nano pins 25 and 27 should be tied together and then connected to a 10K ohm resistor, and the other side of this resistors then needs to be connected to 5v power.
It's also possible to charge the iPod's or iPhone's battery to make use the of internal +3.3v output (18) terminal to connect the USB Data + (27) thru a 47k ohms resistor and the USB Data- (25) thru a 47k resistor to the USB Power source +5v (23). This way the USB function is still useable for normal operations and makes it easier the fit in a plug. The resistors are not to critical 2x 150k's still work.
また、注釈部分には次の記述がありました。
The iPod Nano 4th Gen no longer charges from the 12 V supply on the Firewire pins. If you tie Pins 25 and 27 together and then connect a 10 kOhm resistor to ±5 volts to pins 23 and 15 (or 16), it will charge. If you don't tie Pins 25 and 27 together, it won't charge.