diy iPhone 3G charging/lineout Adapter

[DC Dave]

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.
http://tzywen.com/modules.php?name=News&file=article&sid=696

Sparkfun supplied the dock adapter.
http://www.sparkfun.com/commerce/product_info.php?products_id=633

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

 

[DC Dave]

The size of the dock connector allowed the resistors to be housed within.

It works great, and only cost $5.

 

[CptanPanic]

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

 

[DC Dave]

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]

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]

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.
Thanks,
CP

 

[CptanPanic]

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.
CP

 

[DC Dave]

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]

If you look at http://pinouts.ru/Devices/ipod_pinout.shtml pin 11 is serial ground. I wonder if you need something on pin 21, like the 1MOhm resister that the belkin had.


CP

 

[temp123456]

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 🙂

 

[DC Dave]

Haven't had a chance to try it yet. I'll keep everyone posted.

 

[Havoc08]

how did it go?

 

[DC Dave]

Works great with my iPod, but I didn't get the line out to work with the iPhone. At the time this thread was started, there wasn't much on the market, but now there are different adapters and cables to choose from. I'm currently using a Pocket Dock successfully. Not diy, but it works.

 

[Havoc08]

hmm okay. I want to make a custom dock with lineout and charging and syncing capability.

 

[changedsoul]

I just got a dock from amazon that claimed to be for the iphone 3g. I used it for the ipod touch and the touch plugs into it just fine. One problem was that I got a bad hum when listening to music and charging at the same time. I opened the case up and also discovered that the tip of the 1/8 audio jack was being tied together with pins 3, and 4 ( im guessing the audio left and right), the center ring was being grounded, and the ( what should be ground ) back ring on the plug was open and not connected at all.

All I see is one 75.3k ohm resistor connected to ground, and then wires connecting the back plug to the plug going to the ipod touch / iphone.

 

[Havoc08]

I have not yet found a solution to that problem other than apple designed the iphone 3g wrong with common ground for USB and audio.
I guess a ground loop isolator would work.

 

[changedsoul]

I solved the problem. It was a defect in the design if the dock. I made some cuts on the pcb and some jumpers and it works great now. I have true stereo Audio out and I can charge with out getting hum.