Tab 2 7 (GT-P3110) dock + 30-pin audio out: how to - Galaxy Tab 2 Accessories

EDIT 20130526:
Get the free app "Galaxy Dock Sound Redirector" this will switch the audio to the line-out depending on dock-triggers (desk or car dock).
No need to solder any stuff if you just want to use the Samsung Dock.
If I had come across this earlier, then the thread would not have started at all.
Added 20130527:
I got reports in other forums that some Samsung docks of the same type (EDD-D100) get their output with a Tab 2 7" or Tab 2 10.1" directly to the line-out with a standard 3 pin (headphone) 3.5mm jack connected.
If you happen to have such a dock and Tab 2, can you please report Serialnumber (Bottom of dock) and manufacturing date (on the cardbox of the dock) with your Tab 2 type (7" or 10.1")?
If you are also (or know) a technical guy, could you measure the electrical resistance between pin 13 (13th contact-slot from left looking from front) of the 30-pin jack which gets in to the Tablet and the outermost contact of the line-out (the one you see/reach best when looking in the line-out socket) - and also report it here?
For my (non working) dock it is 3.22kOhm - I suspect for the working ones it would be 4.2kOhm
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This was a lucky success finally - getting the audio out of the GT-P3110 via the 30 pin connector in the EDD-D100, so not using the top headset connector. Audio gets then out of the 3.5 mm socket in the EDD-D100 and connects to the home stereo (or where you want it). Let me report the result first - then some on the history of finding it.
Bottom line:
For direct 30-pin audio out see post #3, with dock see here:
you need a EDD-D100 Samsung Dock
you need a 4 pin 3.5mm audio connector
audio out is tip (1) - left, ring (2) - right, ring (3) - audio ground
mind this is NOT headset out, impedance is much higher but a stereo can well be connected.
pin 4 (mic.) requires a resistor (~1k) connected to pin 3 (audio ground)
voltage measured between pins 3+4 for "audio to dock" ranges from ~0.13V to ~0.37V with resistors from 450 to 1.65k
EDIT-2: Car dock resistor is from 3.3k to 4.8k
Alternate solution: replace the EDD-D100 internal resistor of 3.2k with another one of ~4.2k - then you could use any standard 3.5mm to cinch cable for audio connection. THIS is the way it should have been built right from the start!
Failing steps have been:
getting audio/video cables for P1000:
they just charge via USB
getting the original Samsung Dock EDD-D100WE (white)
syncs on PC, charges with original charger, gives you the "docked" signal, but NO AUDIO on the dock with a standard headset connected or a 3.5mm to cinch converter - audio stays on built in speakers (or headset on top socket).
checking the Samsung Dock with a friends GT-P3100 and original headset has once(!) routed audio via the dock, but then no more
I was complaining to Samsung that such an obvious purpose could not be done with their own devices but after an initial reply from a non-expert who completely misunderstood the problem - the next "expert" wanted to check back with other experts but then silence since weeks.
I could also not discover any special audio adapter which had to be connected to the dock for a home stereo connection and was about to return the dock to Amazon.
But then I remembered that I had another Samsung headset adapter with the older 4-pin layout (not the newer Apple-like as the latest Samsung devices have) - it is the "AARM040EBE". I gave it a try to connect to the dock and immediately it was silencing the device and has routed audio to the dock!
Sadly the pinout (pin 3+4) of the AARM040EBE is not connecting the ground of audio correctly - so you cannot use that straight away You could keep your finger on the botton (this shortcuts pins 3+4) but no listening pleasure this way...
Now some history on my faults and assumptions:
As I did not want to take either device apart, I just measured resistance (1.7k - 2.2k) between pins 3+4 and started making an adapter myself - which failed
EDIT-2: 1.7k is at the upper edge where it works
So I HAD TO disassemble the dock - which went quite well with enough patience in getting the sticky tape glued parts apart. This has finally revealed that pin 30 of the connector towards the device is connected with audio socket pin 3 (upper ring), the audio ground - and that pin 4 (sleeve) of the audio socket is connected to [EDIT: pin 13 (Accessory ID)] via 3.22k (the only component on the PBA). Pin 4 is the microphone connector, but I it also serves other purposes as you will see.
So what happens when you connect a standard 3.5 stereo plug is that you shortcut pins 3+4 and so there is no voltage drop possible between them. However it finally turns out that the voltage between pins 3 and 4 is the key to switch the audio.
[EDIT: its not only the voltage, see later]
EDIT-2: it IS the voltage only, some wrong speculations follow in gray:
My initial attempt to have just resistors create the voltage drop behind the pull-up resistor has left me clueless for while until I measured the voltage drop (not resistance) between pins 3 + 4 of the AARM040EBE in both ways. This has revealed that there is a Zener-Diode inside (1.7 V) which limits the voltage and if reverse connected (this is how it is connected to the Tab 2 as the pins 3+4 are reversed) then the diode is running in connected direction and has a voltage drop of ~650mV. To double check I have also opened the AARM040EBE and it proves like this.
OK - next try for an adapter with pins 3+4 and diode in connected mode from 4 to 3. Strange effect: the device goes in "Car Dock" mode - but audio stays on the speakers - no routing to the dock!
So what now... I then measured the voltage drop that the AARM040EBE was creating and saw it was not 650mV but just ~340mV. So the diode needed a parallel resistor to get voltage down and this way it finally works!
Epilog:
Altering the pinout for the AARM040EBE (3+4 reverse) will make the connector work with the GT-P3110 top socket (including microphone for Skype), but it also puts the Zener diode in other direction and the resulting voltage drop is then 1.2V - which again does nothing to the dock audio.
EDIT-2: if you put a parallel resistor to have resulting resistance at ~1k it should work for both purposes.
I have not tried anything with 30-pin cables directly yet - but it could work in the same way if you want to try out. At least I can use my Samsung Dock for the purpose I bought it for finally.
EDIT: As I noticed the initial assumption of a pull-up resistor would make no sense if the pin 4 would not be connected to anything that evaluates the voltages there. So I re-checked the wiring and I noticed that it is not pin 7+8 (V+), on the flex-cable pins 5,6,7 - but instead pin 13, on the flex cable pin 4. So what you measure between audio socket pins 3+4 is just the signal-forming entity, however the effective accessory detection happens at pin 13 (AID). So it DOES matter that the AID is not just voltage but something more.

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Key to switching is the Accessory ID pin 13. This connects via 3.22k to the MIC-connector (pin 4 - sleeve) on the Samsung dock audio socket - but just to connect something to ground (pin 3) - not for a microphone.
As indicated in my original post this is a ~1k resistor (ok from 450 to 1.7k) from pin 4 (sleeve) to pin 3 (upper ring).
Need to understand how the device knows it is in the dock if nothing is connected to Accessory ID on pin 13. I suspect it is pin 14 (Accessory INT) being connected to ground (pin 15) on the PBA.

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OK, riddle is solved - you can get the 30 pin audio with the following:
must connect pins 14 (Accessory INT) and 15 (Gnd) -> gets you "docked"
must connect pin 13 with ~4.2k (3.2k+1k; may vary from 3.7k to 4.8k) to 14+15 -> gets audio to pins 27 (L) and 28 (R)
EDIT: you should also have the audio-ground separate from power supply ground. So if you can manage this, then connect only Pin 30 to the shield of the audio cables (L+R).
If you like car-dock mode (audio stays on the device) use a resistor in the range of 6.5k to 8k.
Enjoy

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So I did another adapter from a P-1000 cable I bought cheap on ebay. This adapter will not work straight away on the GT-P3110 as connectors are (slightly) different and the Accessory ID pull-down resistor has another value.
You will need one (SMD) resistor to replace the original one from pin 13 (in my adapter it was 12k but should be 3.7k to 5k) to ground and decent skill to disassemble and re-assemble the sockets. The changes to do are:
open the cable distributor and replace the 12k SMD (from pin 13 to ground) with ~4.5k
remove (unsolder) the yellow cinch for composite video - you do not need it for the GT-P3110. This gives you a free PBA connection you will need next step.
unsolder the audio ground (both L+R) from common ground with power-supply and solder to the former composite video cable contact on the PBA. The video connector will later change its position in the 30-pin jack to pin-30 (audio ground). This part is important or you will have noise in the audio when charging with a switching power supply.
Now to the 30 pin:
open the 30pin jack carefully
unsolder the dual (pins 15 + 16) ground
carefully pull the contacts from the plastic socket and re-insert one more left as pins 14 + 15. If you have them separate after the unsoldering of the cable, then you could only move pin 16 to pin 14 as well, of course. They come directly aside the pin 13 which stays where it is.
re-solder ground as before (now pins 14 + 15).
unsolder the former composite video (don't remember where it was)
carefully pull the contact from the socket and re-insert at pin 30 (audio ground)
re-solder as before (now on pin 30).
Re-glue or duct-tape-wrap the sockets - done.
Enjoy!

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that's weird, the guy in this thread http://ls1tech.com/forums/stereo-electronics/1618926-android-7-tablet-install-c6.html said he got audio out thru the dock connector, just no mic input (which is why he did what he did).

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That is very long thread... not sure which adapter he used for checking the mic input, but if the mic has the right resistance then you get the audio from the dock which is the finding I had published. You just don't get it with a standard 3 pin to cinch adapter or a regular headphone (without mic.) from the Samsung dock.
You also don't get it with the 30 pin adapters you can buy which are all for the P-1000.
I have searched very long all over Google before I bought the adapter for P-1000 which did not work, then bought the original dock, expecting it to work straight away - which again did not work - so finally I picked up the task to do it myself.
I was so upset that the original dock did not work and Samsung is not offering cables from dock to stereo. The GT-P31xx is the best selling small tablet and for sure I am not the only one who wants to use its great audio capability at least when it will retire in a year's time.
So I know it works for me exactly like this. I am curious to see some commercial offers for cables now that all details are public. You could also mod some of the cheaper docks.
Sent from my GT-P3110 using xda app-developers app

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sorry for my english XD
I would like to know if there is any kernel to enable the audio and connect a usb dac FiiO e10

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skulls1991 said:
sorry for my english XD
I would like to know if there is any kernel to enable the audio and connect a usb dac FiiO e10
Click to expand...
Click to collapse
Just guessing: you want the 30pin to have digital audio (in/out) via USB? You should ask this in the related kernel threads for the Galaxy Tab 2. I have so far not come across this feature for my devices.
Mind that the DAC in the GT-P31xx is very good (low noise) and you can tune max-volume in a simple way by manipulating \etc\default_gain.conf
If you keep the ground for power and audio separate you should also have no noise (generator) problems in your car.

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tobbbie said:
Just guessing: you want the 30pin to have digital audio (in/out) via USB? You should ask this in the related kernel threads for the Galaxy Tab 2. I have so far not come across this feature for my devices.
Mind that the DAC in the GT-P31xx is very good (low noise) and you can tune max-volume in a simple way by manipulating \etc\default_gain.conf
If you keep the ground for power and audio separate you should also have no noise (generator) problems in your car.
Click to expand...
Click to collapse
How wold one modify that default_gain file to increase the max volume coming from the headphones?

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Quite obvious (google for it), but mind to set file permissions like before. Max value is 63 and you need to reboot to get the increased output.
Sent from my GT-P3110 using xda app-developers app

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So I'm trying to use the 30-pin cable original p3110, you can upload any pictures?

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tobbbie said:
Quite obvious (google for it), but mind to set file permissions like before. Max value is 63 and you need to reboot to get the increased output.
Sent from my GT-P3110 using xda app-developers app
Click to expand...
Click to collapse
could you check this and see if there's anything I missed?

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skulls1991 said:
So I'm trying to use the 30-pin cable original p3110, you can upload any pictures?
Click to expand...
Click to collapse
You cannot use the original cable for audio out. You should get a cable for p1000 as told. For USB you need a USB Host adapter and then check if any USB Audio device would be recognized.
If you should want to connect the device as a flash-drive to a USB car stereo then this would not work as it cannot be connected in MSC mode. It just supports MTP and PTP protocols.
So first tell what you actually want to achieve.
Sent from my GT-P3110 using xda app-developers app

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daniel644 said:
could you check this and see if there's anything I missed?
Click to expand...
Click to collapse
Did you check if it works? You cannot break anything, just rename the original file to keep it. You have to be root to change the file on the system partition, but I guess you know that already.
Sent from my GT-P3110 using xda app-developers app

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tobbbie said:
Did you check if it works? You cannot break anything, just rename the original file to keep it. You have to be root to change the file on the system partition, but I guess you know that already.
Sent from my GT-P3110 using xda app-developers app
Click to expand...
Click to collapse
Yeah, it definitely works, I have to keep the volume on the cars headunit down like 5-6 numbers below where I used to keep it at, I'm thinking I may go back and instead of 63 use like 61, there's just so many spots in it that I just don't know whether I should bump them up or leave them alone.

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daniel644 said:
Yeah, it definitely works, I have to keep the volume on the cars headunit down like 5-6 numbers below where I used to keep it at, I'm thinking I may go back and instead of 63 use like 61, there's just so many spots in it that I just don't know whether I should bump them up or leave them alone.
Click to expand...
Click to collapse
Why get lower in the conf file if you can regulate via the volume buttons out on the tab? Just don't set it to max volume there. Having max power from conf file permits also to use less efficient headphones.
Do not touch any other settings in the conf file, except maybe also the line out which is used for the 30 pin audio out.
Sent from my GT-P3110 using xda app-developers app

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tobbbie said:
Why get lower in the conf file if you can regulate via the volume buttons out on the tab? Just don't set it to max volume there. Having max power from conf file permits also to use less efficient headphones.
Do not touch any other settings in the conf file, except maybe also the line out which is used for the 30 pin audio out.
Sent from my GT-P3110 using xda app-developers app
Click to expand...
Click to collapse
I primarily use my tablet to run audio out to my cars Head Unit so it's just easier for me to be able to blindly turn the volume on the Tab all the way up so regulating the tablets max via this file makes more sense to me then turning it up all the way then back down one notch on the volume buttons.

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daniel644 said:
I primarily use my tablet to run audio out to my cars Head Unit so it's just easier for me to be able to blindly turn the volume on the Tab all the way up so regulating the tablets max via this file makes more sense to me then turning it up all the way then back down one notch on the volume buttons.
Click to expand...
Click to collapse
Can't you do BT Audio streamimg? I find it much more convenient than hooking the device via headset out. It also keeps a separate volume level for this.
Do you get any noise when charging and having the tablet hooked?
Sent from my GT-P3110 using xda app-developers app

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I need a cable that charges the tab and give me the 2 RCA to connect to the amplifier

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tobbbie said:
Can't you do BT Audio streamimg? I find it much more convenient than hooking the device via headset out. It also keeps a separate volume level for this.
Do you get any noise when charging and having the tablet hooked?
Sent from my GT-P3110 using xda app-developers app
Click to expand...
Click to collapse
The bluetooth in my stereo doesn't support audio streaming, it only does the basic handsfree stuff so that's not an option for me, also I just prefer wired anyway. Can't comment on any noise as I haven't set up anything to charge the tablet while it's in the car yet, since this is the only thing I use my tab 2 for I can go about a month between charges so I don't really see the point to put the money into that aspect of the build yet.