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DC Dave 30th November 2008 01:18 AM

diy iPhone 3G charging/lineout Adapter
2 Attachment(s)
After not finding what I wanted in an adapter for the new iPhone I decided to make one to fit my needs.

I wanted to be able to charge the phone using the usb power adapter in my car and also have a line out for audio.

I used the schematic shown here for the charger portion of the adapter.

Sparkfun supplied the dock adapter.

4 resistors and two junk-drawer cables was all that was needed.

DC Dave 30th November 2008 01:20 AM

2 Attachment(s)
The size of the dock connector allowed the resistors to be housed within.

It works great, and only cost $5.

CptanPanic 2nd December 2008 01:50 AM

How did you wire up the line out? Have you verified the line out works while charging?

DC Dave 2nd December 2008 02:20 AM

I connected the audio out cable directly to pins 2, 3, and 4 of the dock connector which are the signal ground, right + and left + respectively.

I did not get a chance to test the iPhone with charging and playing at the same time, but my Nano played fine while charging. I'll test the phone and reply back.

DC Dave 3rd December 2008 01:48 AM

Okay, the iphone charges, but no line out. I'll do some more research and see what needs to be changed. Could be a different pin out compared to other iPods. Or something additional might be needed.

CptanPanic 3rd December 2008 01:54 AM

Yes please let me know. I have read others having to put into airplane mode, etc. Also let me know if you get any cell phone interference.

CptanPanic 3rd December 2008 02:12 PM

There is a chance that you won't get it to work. I read around, and it seems there might be some kind of authentication chip needed to tell iphone that it is ok to send line out and charge. Hopefully this is not the case. I took apart my dock and couldn't really tell.

DC Dave 4th December 2008 01:30 AM

From what I have read on Head-Fi, it sounds like pin 11 needs to be tied to ground to get the line out to work.

CptanPanic 4th December 2008 01:11 PM

If you look at pin 11 is serial ground. I wonder if you need something on pin 21, like the 1MOhm resister that the belkin had.


temp123456 10th December 2008 02:17 AM

Did it work?
Hi all,

Did you guys manage to charge + line out the iPhone 3G at the same time? (did you get it to work without the warning message?)

Thanks :)

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