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I tried a similar arrangement with my Nexus 7, but opted to put the microSD card reader where the rear camera would have gone instead of the space beside the headphone jack (my second choice). I have a 64GB microSD and since the back cover is easily removable, I decided that I didn't need to cut a hole in the cover. I also wanted the Nexus to look completely stock. I was able to solder a small ribbon cable from an old laptop to the pins on the back of the microUSB port, which connected to my microSD card reader. Using a Dremel, I had to grind away a small part of the mid-frame around the rear camera hole to fit the reader, but was able to close the cover with everything in place. Unfortunately, I ran into the same problem with the OTG setup not working when the power cord was plugged in. So I've been looking for an alternate 5V source.

I checked the Con3 pins with a multimeter and found the following:
There are 24 pins on Con3, and pins 1,4,7,11,13,19,20 and 23 are grounds.
Pin 2 and 3 are 1.77V and pin 24 is .11V.
There is no 5V source.


I'm considering simply tapping into the 7.4V lead from the battery and using a 5V voltage regulator like this one:
http://www.radioshac...oductId=2062599
The downside is that is would draw a small amount to power, even when the tablet is turned off. There's also the issue of finding the space to fit the regulator. My other option is just to keep checking pins for 5V.

 

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I don't know the specifics of how the port switches from OTG to charging, but I do know that the SD card works perfectly until I plug in a power cord, then it disables the reader and still doesn't charge. Even after I remove the cable, I still can't get the card to mount unless I reboot the tablet. I read that adding a resistor to one of the grounds will enable charging, but it will still cut off the OTG setup. Connecting the reader to an alternate power source is the best solution, provided that I can find one.
 

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[sub]if you tapped say the pogo pin ground and kept the 5 volt source from the usb ribbon cable connector then the ground would remain constant and not chage.[/sub]
I get what you're saying and can give it a try tomorrow. It's pretty late here.
 

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I actually bought a Samsung Tab 2 7.0 at the same time a the Nexus 7, and the performance of the Samsung was so far below the Asus it wasn't even a fair battle. Also, the developer base for the Nexus 7 is soooo much better than any other tablet I've owned. Throw in the terrible Samsung device support, and it was a vert easy decision.
Anyhow... in regards to the boards, I highly doubt that they use the same boards. Samsung and Asus are rivals and wouldn't share proprietary components like circuit boards. Aside from both being Korean, I think the similarities end once you open the cases. I might be wrong, so it's worth looking at an Galaxy Tab tear-down.
 

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BTW - No luck on using the pogo ground. I've been up to my eyeballs in work, but this weekend I plan to spend some time on this project. I picked up a new variable wattage soldering iron and some resistors. I'm going to try to use everything from the micro USB port, but add a resistor to the back side of the neutral lead to allow charging. Several people have had success with this set-up... using external splitters. Doing it internally is going to be tricky, considering that I have to splice into the lead right behind the port and there's no room. I'll probably have to trim away some of the plastic speaker housing, but it should work. Keep your fingers crossed.
 

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Just a quick heads up... the two red leads coming off of the battery aren't 7.4V. It's is two cell Li-poly pack, and they have leads for each battery. The red wires are each 3.7V, so my idea to use a 5V voltage regulator is out the window.

I've seen about a half dozen people trying this and it all still comes down to one problem: finding an alternate 5V supply. The data leads and ground isn't a problem. The way the micro USB port is set up, it's using the neutral lead on pin 4 as a switch. In it's normal state or when a charger cord is plugged it, the micro USB port works as a voltage "input", but when an OTG cable (which has the neutral lead spliced to the ground) is plugged in, it switches to "output" mode and supplies 5V to the attached device. Plug in a charger while the OTG set-up is running, and the switch shuts off and drops the external device. Supposedly, there's a workaround where you solder a resistor between the neutral lead and the ground and OTG works with charging, but I haven't had any luck. I've read resistor values of 32K Ohm - 100K Ohm working for various devices, and I've tried several values on the Nexus with no success. It we could find a 5V source, we could bypass the whole micro USB port and the neutral switch is a non-issue. I've tried searching for a source, but I've stopped short of disassembling tablet to get to the front side of the main board.
Keep in mind this is just based on observations and research on my end. It's very possible that I'm wrong, and there's an easier solution.
 
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