[Galaxy S III General] AriHell:
Hi there,

So I been looking for a way to both charge and use USB OTG after a short search in Google I found this:

http://www.youtube.com/embed/p10LgZFIawo

basically this guy used a simple USB Y cable which look like this

If you look inside that cable it would probably look like this:

so from that pattern we can see that there is no way that our S3 will charge (frankly saying I don't really know why his TouchPad was charging)

there is a simple explanation why it won't charge, there is something that called "USB Battery Charging Specification" which is some kind of a standard for charging via USB port therefore for the phone to recognize that a charger is connected the D+ and D- should be shorten together or connected through a 200k resistor (BTW to charge an iphone it should sense a voltage on D+ and D- but it is a different story, what I'm trying to say is that it is true for all phones).

we could just connect the D+ and D- in the Y cable and charge but then the OTG won't work because it need the D+ and D- to transfer data

OK so what now? is it possible?

well probably it is possible somehow.

Not long ago I so this laptop extension for the S3 called "Spider Laptop"

Tow interesting thing in this laptop extension the first one is that it charge the phone

the second thing is that it has 1 USB port my guess is it will let you use it as a OTG

(assuming it doesn't have some additional hardware inside)

The user sonic_boom was successfully made OTG cable and charge at the same time for Xperia phones by simply connecting a 100k resistor between sense (4) pin and ground (5 pin)

http://xdaforums.com/showthread.php?t=1822653

but he had no luck with the S3 yet.

Overall we can see that it possible in android devices so why not on S3?

I been messing around in the S3 kernel source code to find some clue if it would be possible

and I found something interesting in max77693-muic.c file (BTW max77693 is a power and battery management IC)

These resistors you see above are used to put the S3 in his diffrent modes, for example the 301Kohm resistor between sense (pin 4) and ground (pin 5) will put the phone in download mode aka USB JIG.

what caught my attention is "ADC_SMARTDOCK" can it be the "spider laptop"? maybe

I was looking for some more clues and I found this in line 1897-1900

to clarify

"chgtyp" - charger type (USB, AC, other).

"CHGTYP_DEDICATED_CHGR" - 500mA charger (standard current of a USB port).

"SMART_DOCK" - probably the "samrtdock" mode.

"TA" - not sure yet (cable type??)

It seem like it would be possible to use OTG and Charge at the same time in "smartdock" mode

To put the S3 in "smartdock" mode we need connect 40.2Komh (as mentioned above) between sense (pin 4) and ground (pin 5)

The only thing left is to try and see!

I will try it and update you...

You are more then welcome to try and report in if it is working or not (I AM NOT RESPONSIBLE FOR ANY DAMAGE)

If you know some other way to make it work I would glad to hear!

UPDATE

So far no luck with 40.2Kohm resistor :(

But maybe it because my 40.2Kohm is actually 40K (damn deviation)

Anyway some findings:

1. The phone is charging at least it saying so, not really left it to see if it is really charging.

2. The phone recognized the charge as a USB meaning it drawing 500mA.

3. By playing with the 4 pin i noticed that the phone need the 4 pin to be shorten to ground just for a second, after the S3 recognized the USB OTG mode I released the 4 pin from ground and it was still working in otg mode.

what made me think that it is possible somehow to modify the kernel and make OTG working, or make it work in other mode for example instead of going in car dock mode (or other mode) with a 619K resistor to enable OTG mode because in car dock mode the phone is charging for sure.