# [Open Discussion] Soldering in Micro sd card reader to Nexus 7/ build log



## Kpa2727

Ok so heres what I got so far. This will be a work in progress since I need a collaberative effort so I don't destroy my new N7.

So what are we starting with? a 8 gig N7

The goal? internally install a micro Sd card 32 gb with upgrade to 64 gb in th future.

Why? Because I can.

Questions i need answered,

Will it charge? It's a tough call, i need more hardware info first

Will this void warrenty? you betcha

Will this risk destroying my tablet? OHHHH yea Experts only!

Do you need drivers? No , This should work just like OTG but internal, using the App Stick Mount.

My background is a huge collection of controller building modding, console building and so on.

So what's the game plan? Take a micro sd card reader, strip it then solder it into the Usb plugs data and power connections. By doing this I feel I would bypass any jumper needs for charging or switching since the card will not physically occupy the slot.

So drop your thoughts below, Scroll down fro pics on progress and thoughts.













































From IFixit, the usb micro port i need to solder into.

Update 7/28::

Did you think this was dead? NAhhhhhhh

I been busy getting my health in order and waiting on my OTG for testing

Progress::

Heres some of the biggest issues i have been figureing out and i've solved just about all.

I've decided on Cat 5 ethernet type of wire for my solder joints, this should keep everything thin since there is no room inside for anything extra.

I've decided to place the sd card just behind the audio jack, this should provide enough room without damage to anything.

forum member Snow02 has been a big help so far in testing mounting and charging configurations, it looks like the Sd card will mount but not charge while mounting, but unmount qand it charges, this works fine for me since i don't plan to be ever plugged in with the sd mounted. I won't fully know till I solder in it. This could be a kernal issue that can be solved with software i'd have to assume, I'm not a Dev so I can't be sure.

Also i'm trying to find out if you can force apps to install to a stick mounted Sd card, it be a great help if someone can input on this since it's my final hurdle.

Once this is solved i can up the 8 gig nexus to a whoping 32-64 gig permantly.

Stay tuned !


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## nhat

1. Why not just use a USB-OTG cable?
2. Do you have a Squaretrade warranty?


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## Kpa2727

I have only mfg warranty and the point being, carrying no extra parts.


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## dadsterflip

I'd be interested in this lol.

Sent from my Galaxy Nexus using Tapatalk 2


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## Kpa2727

I'm pretty sick , I came down with tonsilitus last night, so doctors tomorrow but i'll see what I can do when i'm better.


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## robinthecity

What about the pogo port dots on the external casing? They should offer a USb interface, no? Hope ur Tonsils are back down

Best


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## Thorn11166

Wonder if someone will make a case that uses the pogo pins to add a usb slot or sd slot... Can dream can't i

Sent from my Galaxy Nexus using Tapatalk 2


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## throwbot

Thorn11166 said:


> Wonder if someone will make a case that uses the pogo pins to add a usb slot or sd slot... Can dream can't i
> 
> Sent from my Galaxy Nexus using Tapatalk 2


That, my friend, is actually quite a sick idea

Sent from my Nexus 7 using Tapatalk 2


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## jabsys

This could be a cool project if it works, I'd certainly like a 64gb N7 but I don't think my soldering skills are upto it, good luck.


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## Kpa2727

WEll I been away but I did recieve my new soldering Iron and Went at it, It's too delicate to solder to every usb pin. I tried and if i went any further i'd destroy the N7. The connector is a fine line, u have to balence, heat flux and solder. the connectors are bonded to wire which is sandwiched between plastic. get it too hot and it will melt. On to the pogo pins. I noticed the pogo pis are 4 pins so technically that would be the USB interface. without a pinout though I can't be sure, i have tried to hold the usb wires on them and mount but no luck yet. I plan to tinker with it. I am better now but need surgery. thanks for the wishes,i'll keep everyone updated when i get into it more.


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## frenetic

Kpa2727 said:


> WEll I been away but I did recieve my new soldering Iron and Went at it, It's too delicate to solder to every usb pin. I tried and if i went any further i'd destroy the N7. The connector is a fine line, u have to balence, heat flux and solder. the connectors are bonded to wire which is sandwiched between plastic. get it too hot and it will melt. On to the pogo pins. I noticed the pogo pis are 4 pins so technically that would be the USB interface. without a pinout though I can't be sure, i have tried to hold the usb wires on them and mount but no luck yet. I plan to tinker with it. I am better now but need surgery. thanks for the wishes,i'll keep everyone updated when i get into it more.


POGO pins are: +5v, audio right, audio left, ground (not in that order) so there's no data transfer there


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## Cannonball_CO

Good luck, it would be a nice modification. Have you considered the alternate approach, that is, replacing the Kingston chip on the motherboard?


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## Kpa2727

frenetic said:


> POGO pins are: +5v, audio right, audio left, ground (not in that order) so there's no data transfer there


see i'd normally agree with this but there are 4 pins not 3 looking at the accesories. I'd guess there is data included in the N7 On the Galaxy nexus i'd say yes to what you say being there is 3 pins.

As to replacing the chip, it was my first thought, but it's playing with fire, there is no native hardware replacement support, it's surface mounted. I don't have the technology or machinery to re suface mount a chip if i wanted to. Have you seen the internals? there is just not a hell of alot you can do.


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## kdkinc

Dear Kpa2727:
I think you are a Mad Man









Hopefully the poor defenseless Nex7 will recover from your torture.
Me.I'm still working on spinning my step ladder to change a light bulb.


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## Cannonball_CO

Kpa2727 said:


> As to replacing the chip, it was my first thought, but it's playing with fire, there is no native hardware replacement support, it's surface mounted. I don't have the technology or machinery to re suface mount a chip if i wanted to. Have you seen the internals? there is just not a hell of alot you can do.


Yeah you're absolutely right, it's a surface mount, no "legs" coming out from it on all sides. I didn't notice that detail. I recall people bumping their iPods from 8 to 16 (or higher) a few years back and thought that might apply here as well. Well in that case I am rooting for you even more!


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## Kpa2727

Cannonball_CO said:


> Yeah you're absolutely right, it's a surface mount, no "legs" coming out from it on all sides. I didn't notice that detail. I recall people bumping their iPods from 8 to 16 (or higher) a few years back and thought that might apply here as well. Well in that case I am rooting for you even more!


i'm pretty young {25} i've had my hands in 360 modding, gamecube, wii, wii controller rebuild , i've yet to share anywhere, and even the ipod era, most people bumped Mini's or classic gen. you could take a mini and upgrade it by like 20 gigs cause it used compact flash carts , like the ones found in DSLR's. all they did was open the mini, unplug the old drive, plug in the new and restore with itunes. Same went for classic ipods since they had Hdd's shared with Zunes you could unplug, plug in another and be upgraded.just restore in itunes. I had a brainstorm last night, i'm thinking maybe tap power for pogo pins then data through usb. i may be able to dual charge and mount this way. i would also freee up some space to wire to the connectors. I may give it a try tonight.

Btw my N7 has no damage or solder globs inside, rest assure it'snot being tortured.


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## doubl3h3lix

> i'm pretty young {25} i've had my hands in 360 modding, gamecube, wii, wii controller rebuild , i've yet to share anywhere, and even the ipod era, most people bumped Mini's or classic gen.


I'm from a similar background as yourself. I'm looking at getting the N7 in the next couple of days, and would love the ability to add a uSD card slot internally. I've been looking around, and it appears there may be a header on the board that could be populated? Have you looked into this at all?


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## Kpa2727

I been beat from my job but after i nap tonight , i'm off tomorrow so i plan to go under the hood. got any links on where the header location might be? i'm thinking maybe tap pogo pin's power then data from another location. a one last shot at it, i may try wrapping wire, it's as thin as a human hair but a nightmare to solder.


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## gifton1

Kpa2727 said:


> I been beat from my job but after i nap tonight , i'm off tomorrow so i plan to go under the hood. got any links on where the header location might be? i'm thinking maybe tap pogo pin's power then data from another location. a one last shot at it, i may try wrapping wire, it's as thin as a human hair but a nightmare to solder.


This is awesome Kpa27227 - good luck to ya. Power from pogo and data from usb - bloody genius!


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## Kpa2727

A minor update, :: I sold my N7 today for what i paid plus my shipping cost. I have a chance to buy the 16 gig locally so i'm going to upgrade. Don't worry too much, i'm not abandoning the idea, just taking a break to beef up my soldering skills with wrapping wire then i'll attack it head on. expect like a 2 week break. On another note, anyone else who may want to attempt this or needs input I'll gladly help. A little advice for anyone wanting to attempt this. you'll need Flux for small electronics, a Rosin core solder really fine. You'll need a super fine solderiron. your best bet would be a Weller pencil solder iron, it's like 16 watts. anything bigger or more watts you will destroy the nexus 7 connections.


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## drose6102

I wonder if it's possible to solder on the 64g chip to the mother board and everything work. Anyway you can provide a picture of the internal memory?

I have some soldering skills but would like to see what I would be working with

Edit: never mind this idea is just crazy. The new Samsung 64g internal chip just went into production and who knows if the chip would be compatible with the 7

Sent from my Galaxy Nexus using Tapatalk 2


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## networkproblems

looking forward to your next attempt!


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## Kpa2727

drose6102 said:


> I wonder if it's possible to solder on the 64g chip to the mother board and everything work. Anyway you can provide a picture of the internal memory?
> 
> I have some soldering skills but would like to see what I would be working with
> 
> Edit: never mind this idea is just crazy. The new Samsung 64g internal chip just went into production and who knows if the chip would be compatible with the 7
> 
> Sent from my Galaxy Nexus using Tapatalk 2


I've stated this earlier, you can't mess with the memory chip, i'ts surface mount. you WILL kill the N7 trying to mess with it. You need special machines that do a process called solder flowing or reballing. in the simplest form i can explain, it's like having a river of molten metal or solder, the part rides above it as the componets that need to be soldered touch and travel up the part bonding it to the circuit board. it's like tryinng to add more memory to a onboard chipset on a motherboard. it's next to impossible. the next problemis software, firmware and so on are all configured to that chipset in there. you can't just ad memory. lastly the goal is to com up with a way to do this that normal people on here can do or have other people do for them. in basic terms, a quick down and dirty way to add memory. i want to get in and get out without breaking the unit. i beeen looking into a way of modifying N7's configuration forcing it to install from the play store to the memory card. i saw a few xperia articles with ADB command re routing the install directory to the memory card auto matically. so i may have a way to make it treat it like expandible memory. I do have pics of my solder attempts btw but I wanted to upgrade my N7 and post a collection all t once instead.


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## Thorn11166

would it be possible to make a switchable cable that could operate as an otg cable/charge cable extension? if so someone could build that into a case, sure it would have a little more length at the bottom bezel but it would be pretty sweet to have a usb port built into a case.... just pondering


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## Kpa2727

Thorn11166 said:


> would it be possible to make a switchable cable that could operate as an otg cable/charge cable extension? if so someone could build that into a case, sure it would have a little more length at the bottom bezel but it would be pretty sweet to have a usb port built into a case.... just pondering


This is actually super simple. There is essentially 4 wires for usb and the otg adds a extra ground so it's detected like it is. You have 2 options, a double pole throw switch that severs the data connection or a single pole throw switch that disables the secandary ground, ether one wuld reseult in a switch for charge and a switch for data. the problem here is a the case. cyurrently I have not seen a case that has space to hide a otg cable.

Quick update, I been tracking down my 16 gig, i finally got a order n at gamestop then they got backordered till August 31st. So now I'm on the hunt , then staples came instock with free shipping so i ordered it in i will have mine by friday. I miss my tablet dearly. So in 24 hours i went from my Galaxy nexus to a Razr maxx to a Galaxy S3 then purchased a N7. Talk about trading up.


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## throwbot

Man it really sounds like you know what you're doing, and if it can be done it seems like you're the man for the job.

I gotta come out and say it, tho- I was wondering how quick you'd be to crack open that nexus and risk its life, lol. I'm not blaming you for holding off til you're ready- hell I wouldn't even think of risking mine.

But I'd love to see this idea come to fruition. Good luck on your mission.

I did not mean for that to rhyme. I'll try not to do it next time.

Edit: nyuck nyuck. Sorry, its really early and I'm sitting in my car bored to death.

Sent from my Galaxy Nexus using Tapatalk 2


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## sonofskywalker3

Have you considered just using a usb drive instead of a microsd reader? They make some very small usb drives, like the verbatim tough and tiny. 32 gigs, and the chip itself may actually be smaller. Just a thought.


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## Kpa2727

sonofskywalker3 said:


> Have you considered just using a usb drive instead of a microsd reader? They make some very small usb drives, like the verbatim tough and tiny. 32 gigs, and the chip itself may actually be smaller. Just a thought.


I think you're missing the point i'm stuck at. To put things in perspective, the N7 has no room for anything, you can't run wire even under the back cover, there is just no room. the only gap is between the audio jack and case. there is enough space to fit a micro sd reader. There are 2 goals by going this route. you don't need to resolder to upgrade the chip in the future. 2 you will never make a usb drive as thin as the reader is, this reader all flattened out is almost thinner then 2 micro sd cards layed on top of each other. that's pretty thin.

On to the hurdles i'm stuck at. a viable Data point to tap into , i'm going to use the power pins or pogo type plugs for power, i need to find a better data connector point though. then it's solved.

To answer about how long before i go under the hood. well maybe a week after i get it, should arrive friday. my biggest thing is digging for schamatics and pinouts to accomplish the goal. then i'll go diving in. also i don't want to rip out all that glued down copper shielding , i'm sure it would be a nightmare to re assemble. This is becoming more of a pet project though. I'm famillar with backwards re engineering when i put a wii controller inside a snes controller, that took a long time to figure out due to space constraints. but i built it. it's just a matter of finding a soloution then simplifying it and making a practicle use. so that anyone can solder one in with practice.


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## number5toad

I love this idea, but I couldn't trust myself to open my baby up and mess with her intestines.

now if you were to tell me how to replace the USB end of an SD card reader with a micro USB plug for USB OTG use....I'd pay very, very close attention.


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## Kpa2727

so you want the male end of a usb card reader to go to the male end of a mirco usb plug? like a otg adapter but hardwired to a reader?


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## Kpa2727

this guide answers your question. http://forum.xda-dev...d.php?t=1092493 it's fairly simple, u just use the reader in place of the usb cable. You will need to figure out your sd card readers pin out and which is positive or negitive. this can be achieved by figureing out wich way it plugs into the usb.


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## number5toad

pretty much exactly what I was looking for, thanks!


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## Kpa2727

Np, quick update : i been going through helll trying to get a good N7 It's sold out damn near everywhere till the 30th or so. I got my hands on 2 one from stables but it had a loose screen and massive light bleed. I canceled a preorder at gamestop to wait for that crap. So gamestop sold mine and i found a 16 gig at walmart. I picked it up and as i'm opening it in the car, sealed stickers and all the damn thing has fringer prints under the plastic on the glass, looked like someone ate a doughnut and played with my N7 I was pissed. So the back even had glue residue like a sticker was stuck to it. I powered it up , all looked good but when i activated at home i found a defect in the very tip top right in pitch black lifht. it's like someone put a flaw in my Lcd. it's not noticible in normal use but noone has one, so i'm stuck for a little while, I'll continue my research though and hopefully have a answer soon. Asus make more of these things, wear gloves , eat less dougnuts !


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## iAppleDev

Just have to find power and data (maybe the rear camera data's & power?)


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## Zane_Grey

That looks great! What did you use to cut the hole?

Sent from my Nexus 7 using Tapatalk 2


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## iAppleDev

Zane_Grey said:


> That looks great! What did you use to cut the hole?
> 
> Sent from my Nexus 7 using Tapatalk 2


Just an Razor knife and pocket knife thx


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## iAppleDev

Anyone know the pinout of Con3?


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## ashclepdia

iAppleDev said:


> Just have to find power and data (maybe the rear camera data's & power?)


What rear camera??
Sent from my Nexus 7 using Tapatalk 2


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## Kpa2727

Very nice and clean, try tapping the pogo pins for power then maybe u could try tapping data theough the usb. I been working long days as lead tech so i havent had any free time. great progress though.


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## ED2O9

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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## ED2O9

Kpa2727 said:


> try tapping the pogo pins for power


There's no power output from the pogo pins. There's a ground, right and left speaker outputs and a power input.


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## Kpa2727

[sub]


ED2O9 said:


> There's no power output from the pogo pins. There's a ground, right and left speaker outputs and a power input.


[/sub]
[sub]I was wondering about that, i kept hearing the pogo pins feed stuff but it made no sense to me. Well only thing left as said is a 5 volt source, my guess the speakers feed .5 to 1.5 volts so thier out, the screen might take 5 volts to run. I don't get it though. 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. my understanding of OTG and charging is the ground switches due to charging mode from a ground to a neutral. that then turns off otg but enables charge. by keeping a different ground, that should fix the issue.[/sub]


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## ED2O9

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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## ED2O9

Kpa2727 said:


> [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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## Kpa2727

It's 2 am i have to work at 8 am i just wrapped up a 10 hour day without a lunch or break. i feel the pain.


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## r4ptor

Ok, so that i'm getting this right.

the only problem is to get a 5V connector on the Nexus 7? With this connectionpoint it should be possible to solder a micro sd card reader to the micro usb port(and solder the pin 4 of the micro usb port to ground to get usb on the go)?


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## iAppleDev

Yes that is right. I need some one to scope the board for other possible data+/- lines and 5+/- or I'm stuck using the MicroUSB lines.


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## r4ptor

Ok, so why don't grep the 5V over the battery and get it down to 5V with a voltage divider?


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## Kpa2727

couple of reasons, its a constant draw on the battery and finding a reguator that small can't be a easy task. I got worf, i have to have surgery next wed, i probably will be away for 2 weeks or so from this thread. good luck guys.


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## iAppleDev

Kpa2727 said:


> couple of reasons, its a constant draw on the battery and finding a reguator that small can't be a easy task. I got worf, i have to have surgery next wed, i probably will be away for 2 weeks or so from this thread. good luck guys.


Worf sorry to hear that. I wish you luck


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## r4ptor

Oh crap, sorry to hear that. Good luck and get well


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## Kpa2727

thanks guys, i'll still check in till around tues or so surgery is on wed.

i almost forgot, as for the tiny card readers i got mine on ebay for around 2-4 bucks. look up "micro sd card reader mini".


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## nst6563

Does anyone know what switch the Nexus7 uses for the usb? For example, http://www.ti.com/lit/ds/scds325/scds325.pdf is a TI chip that also displays the impedence values for the ID line on the micro-usb port. One of these impedence values may be the key to getting the memory card reader to work at the same time that the device is charging.


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## maaneeack

Couldn't you tap the wifi/bluetooth/gps or camera to get the power?


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## nst6563

I noticed that besides the spot above the headphone jack, the other nearly perfect spot for say a small 64GB thumb drive would be in the empty housing of the rear camera. I have a sandisk 16gb drive that would fit right in there if a half a mm was shaved off the sides of the pcb on the flash drive (which there's plenty of space for that small amount).

Also - to get power from the pogo pins...maybe it needs to be tapped before the diode. If I'm not mistaken those pins should be protected via diodes to prevent 'wrong way traffic'.

I'd be concerned about charging and having it mounted at the same time. example would be transferring from pc to the tablet via usb cable. If I understand correctly, this would unmount the usb and go into data xfer/charge mode.

There are some datasheets for usb controllers out there that list the impedences for the ID line in the micro-usb spec, maybe one of those is the key to having both charging AND mounted at the same time. I believe 36k is the resistance needed...but would need more confirmation and I need another flash drive and some connectors to find out.


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## Kpa2727

something intresting i noticed was that the samsung tab 7 inch is a spitting image of the nexus 7, same form factor, same buton layout, same beveled edges, the samsung has a camera and a IR blaster. it's 250.00 with a dock. not a bad deal.one was returned at work the other day so i glanced over it. now onto the point. I can almost hinge bets they use the same board with different plugs. the golden ticket is probably in the FCC records disclosed of the devices. probably if you pull thos schematics, youll have most of the answers.to all the comments about before diodes, i highly suggest you pop the cover or research some pictures. damn near half of the N7 is surface mount stuff. you need a damn needle to solder onto that stuff. with public tools you wouldn't be able to do much, with commercial technology you'll sink 2 times the value of the tablet into it just for a sd card slot. i encourage development but practicality guys. were looking for a simple connection that's feesable for everyone with solder skills to do. I'd say nail down a solid source to enable usb first, then work out host and charge functionality. lets be honest, you'll never need to charge and watch movies more then the life on the tab. it kills me when i read about it, you should easily be able to get through 2 movies before needing a charge.so whats the hassel in adding all these other road blocks? lastly Hdmi out isn't even capable if yet or ever will be. so why worry about a charge right now and host? one more thing if you need storage and charge so bad, just move the file with Root Explorer to internal temporarly.


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## nst6563

I did crack it open and unfortunately my eyes aren't what they used to be and I don't have a magnifying glass to read what's on the smaller smt chips. I have no problems soldering on a level that small. The 36k resistors were smt and weren't much hassle, most people just need practice.


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## ED2O9

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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## ED2O9

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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## nst6563

What value resistance? I have some SMT resistors to borrow from and those will fit better than the standard size. Depending on what the value is if I have it or not. I tried 36k with no success, but I didn't solder to the inside of the nexus, I soldered to the otg cable I made.


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## iAppleDev

Found this USB HUB and it fits perfect.


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## nst6563

I see you've got connections going to the card reader and the hub, and possibly to the usb port on the nexus. Do things work this way? Does it charge and use the reader at the same time?

:EDIT: took a closer look and it looks like the other set of wires aren't connected.


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## iAppleDev

nst6563 said:


> I see you've got connections going to the card reader and the hub, and possibly to the usb port on the nexus. Do things work this way? Does it charge and use the reader at the same time?


 no its still just in mock up and not connected yet, but it does still close up fine.So I'm pretty sure a hub is a go(for me anyway) and still have room for some flash storage that will go where the rear camera should have gone or just beside the hub


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## Kpa2727

Shame on the ground, i dread tapping the usb till parts are avalible in case i burnup the usb cable inside.


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## nst6563

can you just solder "extension" wires to the onboard connectors? This way you wouldn't be working directly with the onboard circuitry, but rather the extension wires that are attached. Sort of like testing an existing circuit with an external breadboard.

:edit: Couldn't the 'common ground' be gotten at it's source on the battery? There are 2 black leads from the battery, which both connect to a copper trace that seems to go around the board. Upon looking closer, there looks like some spots for filter caps from the other leads from the battery to the ground. I don't think finding the ground would be the issue, but rather the 5v or +/- data points.


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## Kpa2727

getting the ground from the battery might work it's probably like a mera battery so center ground is neutral and can chge, outer ground. furthest from red should be a solid ground. a guy just figured out mounting usb as main storage so were super close. his method may bypass and allow charging too. it's what i tried to do but couldn't find any proper tuts. it's identical to the xperia play mod. btw 2 days till surgery and counting.


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## nst6563

I saw that post and have yet to fully read it. There are plenty of ground points on the board according to some tests I was able to do with a meter today. I was also able to identify the data +/- points away from the fragile ribbon connector. I soldered wires to them in prep for mounting a new drive internally. I also tapped the power and ground from the smt ribbon cable. I tucked away the wires for later use, I'll post some pictures in a while after I'm done making some notations on them.

Good luck with the surgery.

:EDIT:

Pardon the images if they're very clear ....I took them with my SGS3 since our camera is full of sand from the beach (thanks kids!).









By nst6563 at 2012-09-02









By nst6563 at 2012-09-02









By nst6563 at 2012-09-02


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## Kpa2727

wow those data points on the board are sweet. I may bust into them a lil later before the Operation. thanks , i'll post back results if i can get this done in time.


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## ED2O9

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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## nst6563

The reds are 3.7, the others are 1.7. I haven't dismantled mine to get to the front either, and most likely won't until I have enough funds to replace something should I break it.

Here are a few good reads on USB OTG and charging specs. It almost seems like it's fairly specific to the usb controller the tablet uses. The one thing being in common is the resistance on the ID line to activate certain functions.

http://www.ti.com.cn...001/sszy001.pdf

The host (A-device) would be the Nexus7, the peripheral (B-device) would obviously be the drive. That link to the TI document lists that the controller itself boosts the voltage to the B-device when it's entered as the peripheral.

According to WIKI:
"
* OTG Micro Plugs*

With the introduction of the USB Micro Plug, a new plug receptacle called Micro-AB was also introduced. It can accept either a Micro-A plug or a Micro-B plug. Micro-A Adapters allow for connection to Standard-A plug type USB cables, as used on standard USB 2.0 Devices. An OTG product must have a single Micro-AB receptacle and no other USB receptacles.[sup][4][/sup][sup][5][/sup]
The OTG cable has a micro-A plug on one side, and a micro-B plug on the other (it cannot have two plugs of the same type). OTG adds a fifth pin to the standard USB connector, called the ID-pin; the micro-A plug has the ID pin _grounded_, while the ID in the micro-B plug is _floating_. The device that has a micro-A plugged in becomes an OTG A-device, and the one that has micro-B plugged becomes a B-device. The type of the plug inserted is detected by the state of the pin ID .
Three additional ID pin states are defined[sup][4][/sup] at the nominal resistance values of 124 kΩ, 68 kΩ, and 36.5 kΩ, with respect to the ground pin. These permit the device to work with a USB Accessory Charger Adapter which allows the OTG device to be attached to both a charger and another device simultaneously.[sup][6][/sup] These three states are used in the cases of:
A charger and either no device or an A-device that is not asserting VBUS (not providing power) are attached. The OTG device is allowed to charge and initiate SRP but not connect.[sup][6][/sup]
A charger and an A-device that is asserting VBUS (is providing power) are attached. The OTG device is allowed to charge and connect but not initiate SRP.[sup][6][/sup]
A charger and a B-device are attached. The OTG device is allowed to charge and enter host mode.[sup][6][/sup]
USB 3.0 introduced a backwards compatible, SuperSpeed extension of the Micro-AB receptacle and Micro-A and Micro-B plugs. These contain all of the pins in the USB 2.0 Micro and use the ID pin to identify the A-device and B-device roles. Additionally they contain the additional SuperSpeed pins."
http://en.wikipedia....i/USB_On-The-Go
Here it lists a "standard" impedance specification, however it seems that not all controllers must adhere to the standards and according to another document which I can't for the life of me find right now there were a number of impedance ranges for use on the ID line.

There's also good info in this article http://www.maxim-ic....dex.mvp/id/1822 which also mentions the usage of HNP or SRP which could simply be a kernel patch to allow such a device to charge via setting the HNP.

To get 5v it may have to be coming from a separate circuit with the source from the battery leads to 'sum' the voltage output of the battery to get 5v. With small SMT componets I wouldn't see a problem fitting something similar to that to where iAppleDev has a usb hub placed

I honestly think the answer is in software at this point to activate the charge function. For hardware source of 5v I think a simple op-amp based summing circuit would be the best option if one isn't found on the board itself.


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## iAppleDev

Hub fits I just need to come up with a 5V power somehow got the Data and ground figured. Can someone come up with any ideas to create 5V power, maybe some fancy circuitry to bump the power from battery to 5V?


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## nst6563

To get the 5v, it's possible to simply sum the two power inputs from the battery (3.7 and 1.x) with a zener and a resistor. OR - get fancy and use an op-amp circuit to give the 3.7v line a small boost. I'll see if I can mess with something this week for adding the two voltages via tiny circuitry. It's been a while since I took those EE classes so I'm certain I'll end up toasting a resistor or two 

Wonder how the surgery went? Hope all turned out well.


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## iAppleDev

nst6563 said:


> To get the 5v, it's possible to simply sum the two power inputs from the battery (3.7 and 1.x) with a zener and a resistor. OR - get fancy and use an op-amp circuit to give the 3.7v line a small boost. I'll see if I can mess with something this week for adding the two voltages via tiny circuitry. It's been a while since I took those EE classes so I'm certain I'll end up toasting a resistor or two


Thx for all the help. Think it can run off the 3.7 alone


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## nst6563

I think just a micro-sd reader might be able to, but not a usb hub since it has to pass the voltage and current on to the slave devices. I could be wrong though.

I didn't get a chance to throw together a simple circuit to add voltages this evening, up to my eyes in work. Hopefully this week I can or someone else can hop in the bandwagon and beat me to it.


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## jimsmith1210

@People here

Why did you guys make it internal as apposed to an external thing?


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## mentose457

jimsmith1210 said:


> @People here
> 
> Why did you guys make it internal as apposed to an external thing?


There are several reasons you don't want to mount it to the outside of the device: It could get torn off, cases would no longer fit the device, and it would look like shit.

Observe iAppleDev's picture above. The card reader is mounted on the bottom right hand corner on the tablet. With a bit of trimming on the back cover it can be accessed with the device completely assembled.

I haz no sig


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## nst6563

Exactly what Mentose457 said. Not to mention that the otg cable interface 'hanging' from the tablet will eventually stress the micro-sd connector enough to slightly distort it and cause the connection to fit loosely.

There are a couple threads over on xda with the same pursuit. Check them all out, all are good work towards a possible solution. There was even someone on xda that was able to use the external otg as the primary sdcard yielding 64gb of space.

Still a long way to go yet though. I wish I had my tablet here, I could do some more testing on it. Unfortunately it's traveling with my son for the next week.


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## Kpa2727

Hey guys! I been stil recovering from surgery i had some complications during surgery. I think it prolonged my healing time. I been reading while I can, You guys are making great progress though. 1.5 volts is usually standard protocol up to 5 volts. the micro sd reader or usb drives should be capable of 3.7 volts running. only way to know is to give it a whirl.


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## Snow02

It's a waste of time looking for power for the usb reader. You still won't be able to mount it and have the tablet charge at the same time. Has no one yet attempted to mount external storage via OTG and charge through the pogo pins? That's your only option as far as I can tell.


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## wizayne

hopefully he didn't take your n7 into the sandbox like your poor camera lol 

when this come to fruition I may actually buy an n7 and retire my Xoom. not having 64GB (32+32) really killed the feasibility if ever buying an n7 which is too bad because it would've been a very amazing machine otherwise..Hell I almost skipped getting my gnex because of no sd and only 32GB onboard.

good luck!

Sent from my Galaxy Nexus using Tapatalk 2


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## Kpa2727

Snow02 said:


> It's a waste of time looking for power for the usb reader. You still won't be able to mount it and have the tablet charge at the same time. Has no one yet attempted to mount external storage via OTG and charge through the pogo pins? That's your only option as far as I can tell.


You know as for someone who calls lots of hard work a waste of time you haven't even read progress. as for pogo pins we discussed this. pogo pins do not supply power just ground and audio for docking abilities. It's doable we just need time due to no schematics being avalible. i still don't see what the hell your need to charge and watch movies at the same time is? i played gameboy for a solid 6 hours with my ps3 contoller over bluetooth on the Nexus 7 and lost barely half my battery. Since storage unmounts and remounts between charging I see no complaints. If you need the N7 to be on charge while you have acess to it's external memory i feel you might just have a problem with responsability of keeping your stuff well maintained.


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## kevincat3556

Kpa2727 said:


> I've stated this earlier, you can't mess with the memory chip, i'ts surface mount. you WILL kill the N7 trying to mess with it. You need special machines that do a process called solder flowing or reballing. in the simplest form i can explain, it's like having a river of molten metal or solder, the part rides above it as the componets that need to be soldered touch and travel up the part bonding it to the circuit board. it's like tryinng to add more memory to a onboard chipset on a motherboard. it's next to impossible. the next problemis software, firmware and so on are all configured to that chipset in there. you can't just ad memory. lastly the goal is to com up with a way to do this that normal people on here can do or have other people do for them. in basic terms, a quick down and dirty way to add memory. i want to get in and get out without breaking the unit. i beeen looking into a way of modifying N7's configuration forcing it to install from the play store to the memory card. i saw a few xperia articles with ADB command re routing the install directory to the memory card auto matically. so i may have a way to make it treat it like expandible memory. I do have pics of my solder attempts btw but I wanted to upgrade my N7 and post a collection all t once instead.


Droid days taught me "setinstalllocation -1" lol
Sent from my Galaxy Nexus using RootzWiki


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## nst6563

wizayne said:


> hopefully he didn't take your n7 into the sandbox like your poor camera lol


Got my n7 back....no sand! He didn't get to take it to the beach though like the camera 
Not sure if I'll have any time to mess with those data points and the voltage points since we're moving here in 10 days. Moving is always hell.
I've got the inside pre-wired though, so if I get the chance it shouldn't take long.

Problem with tapping into the 3.7v from the battery is that the flash drive would be using power even when the tablet is off.


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## littleguy

I've been avidly following this thread and several others over at XDA that are trying to accomplish the same thing. While Snow02's post may come across as a little impatient, he (like me) seems concerned about people spending a long time working towards what is already known to be a dead end. He is spot on in his analysis.

After researching numerous threads and the official USB specifications, here are the conclusions I've drawn.

- If you permanently solder the reader into D+,D-,GND, and ID pins, then it still doesn't matter where you get the +5V from or whether the reader is mounted or not. The device won't charge. This is because shorting the ID pin to ground forces the Nexus into host mode, at which point the stock kernel disables charging. Even if the +5v comes externally, it still won't charge. I (and many others on these forums) have verified this directly through testing (see first attachment). Conclusion: you need a way to manually toggle the short between ID and ground, otherwise your device will stay in host mode all the time and never charge. (A kernel mod *might* also solve the problem, but I'm not a kernel dev so I can't speak definitively.)

- If you provide a switch to toggle the ID pin, you still won't be able to connect the stock charger (or any high-speed charger) and use your internal reader at the same time. That's because these chargers short the data lines together, rendering the card reader uncommunicative while charging. Unlike the last item, this is purely an electrical issue that cannot be solved through software. Some people may be ok without simultaneous charger/reader, while for others it's a show-stopper.

- If you permanently solder the data lines from the reader to the nexus, you will have problems if you ever plug the nexus into a PC. Regardless of whether the id pin is shorted or not, you now have two devices - the PC and the reader - tied to the same data lines. Conclusion: if you want to retain the ability to connect PCs or OTG cables to the Nexus's external receptacle, you will need a way to manually switch the data lines between the internal and the external device.

I encourage everyone to look at the following threads, if you haven't seen them already:
http://forum.xda-dev...d.php?t=1884163
http://forum.xda-dev...d.php?t=1866988
http://forum.xda-dev...d.php?t=1854904


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## nst6563

I think that the most important piece we're all missing (besides schematics of course) is the fact that it's unknown whether or not the n7 will respond to impedance on the ID pin. Standard USB specs allow for varying impedance on the ID line, and it's up to the device to detect and enable/disable features based on the value of that impedance.

I'm not a kernel dev either, but there should be a way to check for those impedance values. Roms like ParanoidAndroid have native support for OTG drives while the stock based roms require stickmount or other similar software. Maybe it's more than just a kernel hack to enable functions - who knows. Looooong way to go.

There's a thread on xda where a link to a micro-sd slot was linked to on Mouser which had a switch integrated into it. That would be ideal for use in this situation to trip the ID line to ground when the micro-sd is inserted.

btw - I tried the micro-usb to HDMI mhl adapter from the sgs2 and it doesn't work for the nexus







Maybe that's a kernel patch too? I cracked it open to look inside but didn't have the time to poke around and do tracing. Now it's packed in a box until after I move.


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## littleguy

nst6563 said:


> Roms like ParanoidAndroid have native support for OTG drives while the stock based roms require stickmount or other similar software. Maybe it's more than just a kernel hack to enable functions - who knows. Looooong way to go.


I may be wrong, but I think effectively all they're doing is baking the stickmount app into the kernel.


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## nst6563

littleguy said:


> Yes, this is another important question. In my searching, I have not yet found the answer. It will all depend on the capabilities of the chips on the nexus motherboard, whether or not they can measure the impedance on the ID pin. If they can't measure the impedance, then there's not a whole lot the software can do. Here's a really good explanation here from another thread:
> 
> My hunch is that, since the OTG+charge spec (ACA) was only ratified in December 2011 (and updated in March 2012), there were no ASICs in production yet with this capability at the time the Nexus motherboard design was finalized, and hence the Nexus 7 is a "category 3" device as discussed in the link.
> 
> On the other hand, you could just fake it and patch the kernel to think it's attached to one impedance or another. Then you'd just have to be sure the software state was always in sync with the actual hardware configuration.
> 
> I may be wrong, but I think effectively all they're doing is baking the stickmount app into the kernel.


very well could be baked into the kernel or the rom itself. It does mount in a different location - but then again TWRP can use the OTG drive natively as well. I'm not a developer so I have no clue









Possible the newer revisions of the N7 will have a ratified chip in them. One can only hope.


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## nst6563

http://dl.dropbox.com/u/47767898/me370t.pdf

Let me know if the link doesn't work.
Hopefully someone that can read schematics better than I can make sense of the section Titled "T30 USB, HSIC, ICUSB"

Looks like there is a function defined by a 100k resistor to ground on the ID line. Below that, there are also specifications for an eMMC device.


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## deltaechoe

Honestly i just use cloud storage since i always have my phone on me (to tether) and rarely leave areas with 4g and power outlets


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## born2model3d

Hi guys,

What happened? why no updates..

Well I may be a bit late to this topic and since the only things I repair are my gadgets and my desktop PC, I will say I have a hopeful solution...

Till now, we have everything we need to integrate the micro sd card inside the Nexus 7, except for the 5v power source. But as LittleGuy said, the tablet won't charge even if we do find the source as the tablet switches to host mode.

Now, what if, instead of finding a new source for the sd card, we find a new source for the battery. The battery can always be charged irrespective of the state of the micro usb/otg, its just the circuit that disallows it, right.

So, here is my solution, we disconnect the power cable from the micro usb and connect it to the micro sd card.
Then we take the input power line from the pogo pins and connect it to the micro usb port on the nexus 7.

This way we will be able to charge the phone, even if the tablet is in host mode. Also, as the micro sd is technically connected to the usb micro sd we won't need any software modifications/drivers to get it working.
I am pretty positive about this...
Now I leave it onto you harcore modders


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## zedd82

I know this is an old thread, but have you looked into using this ROM http://rootzwiki.com/topic/37755-timurs-kernel-usb-rom/? It allows the use of OTG and charging at the same time. Might be worth a look if you really want to do this.


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## Natelion65

Why dont you partition the micro sd?


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