charging ipod touch with generic USB chargers or some usb port win2000

Discussion in 'Accessories' started by quartz12h, Nov 8, 2008.

  1. quartz12h

    quartz12h New Member

    Joined:
    Nov 8, 2008
    Messages:
    3
    Likes Received:
    0
    Most chargers don't give a voltage on the inner pins (D+ and D-). The ipod touch and iphone (not the older ipods) simply don't charge unless there is about 2.2-2.4 volts (no current though) on both the inner pins.

    This is the most revlevant article I found. I though you all should know.
    http://forums.macrumors.com/showthread.php?t=464862

    To bring about 2.3V to the data pins, basically just divide the voltage like this: put a 82 Kohm resistor between the 5V pin and the middle ones and a 66 Kohm (I used 68k) resistor from there to the ground connection.

    The simplest material is to get a USB extension cable (the type A connectors, 1 end male, the other female), the shortest you can find/buy since it's is only gonna serve as adapter, cut it 6 inches from both ends and discard the middle portion. Prepare the 2x4 wires by stripping their tip naked for about 3/4 inch. Twist 1 end of the 2 resistors together with all 4 data wires (usually whites and greens). As you can guess, this is not a USB extension anymore!!! it is JUST FOR CHARGING ON USB. This tip is the 2.2-2.4 volts. Twist both red wires (+5V) with the 82k other tip. Twist both black wires (ground) to the 68k other tip.

    Ensure all tips are not touching each other. That should be easy since the resistors are quite stiff. If you have a multimeter, test that you have continuity of red 5V end-to-end, data white+green end-to-end and black ground end-to-end. Verify that you have 68kohms between the ground and the data wires, and 82k between the red 5V and the data wires. If so, plug the usb wire to your old adapter or to the computer and check with a voltmeter that you have about 2.2-2.4V between ground and data wires.

    If so, well that's it! You can try charge your ipod touch or iphone, you should hear the sparks sound, and see the big battery icon (red or green).

    Tape all the tips separately to avoid shorts between wires and then tape them all together cleanly. I hate electrical tape because it tends to become gummy after a few years of flexing. Duck tape could do. You could also simply stuff the whole thing inside a pill bottle: right after cutting the original extension cable, drill holes of the cable diameter on the bottom of the bottle and in the top cap and insert the cable (the connector ouside the bottle of course!).

    Color codes: http://en.wikipedia.org/wiki/Resistor_color_codes
    USB pinout: http://pinouts.ru/Slots/USB_pinout.shtml

    I have no clue why my good old usb 2 ports won't charge the ipod on my home PC on win2000. I guess the ipod touch driver on XP is doing something with the data lines, like leaving them in unknown state (according to USB spec, a 2.4 V is neither a 0 or 1, "single ended" or "differential"). In the end, the usb port clearly sets a 2.4V there somehow.

    I would love of some coder could write a tiny program that just does that part and brings the 2.4V. Anyone?
  2. Maxomous

    Maxomous New Member

    Joined:
    Jan 2, 2008
    Messages:
    22
    Likes Received:
    0
    Device:
    iPod touch
  3. quartz12h

    quartz12h New Member

    Joined:
    Nov 8, 2008
    Messages:
    3
    Likes Received:
    0
    Well, I admit you must be a god... Silly of me. Funny that your article didn't show up on any search engines. One thing I gave the ipod fans is a practical solution, while you gave the electrical diagram. I guess the both of us can write a decent article that can reach a majority. Thanks for adding the cross reference.

    From the old article replies:

    It is not possible to cause damage by shorting these pins. The USB port spec has 45 ohms on both data wire. Should you short them, even at 5V, there would be only 110mA. You can trust that exposed computers ports are made robust and to limit current.

    That being said, such wiring is not going to allow you to sync your ipod, of course, since the D+ and D- are not free anymore. This electronic is only good for converting USB chargers that only give 5V and ground voltages. You typically would not use this home made adapter on a computer where you intend also to sync up. There is no data pins to short in on the USB charger in the first place, but it does set both the ipod inputs to 2.4V. Remember that USB physical layer is full duplex and it is made so that both end points can output voltages on the same wires.
  4. Maxomous

    Maxomous New Member

    Joined:
    Jan 2, 2008
    Messages:
    22
    Likes Received:
    0
    Device:
    iPod touch
    well, i must say, with your smarts and my amazing drawing skills, we could rule the world!... /forum

    Please Register or Log in to view images



    But dont worry about not being able to find my thread previously, easy mistake! your quite welcome to steal the picture if you want? the link is: http://img179.imageshack.us/img179/3180/ipodchargergv2.jpg
    your choice?
    ------------------double post merged------------------
    oh i forgot, i was just reading your thread and it didnt say the resistance, but to be honest neither did mine! I tried charging my touch this way with a variable power supply and kept wondering why my ipod wasnt charging at all, even over night, then realised it only went up to 300mA!

    i think somewhere, you should chuck in "1A(1000mA)"

Share This Page