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

98801 Views 91 Replies 33 Participants Last post by  Natelion65
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


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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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.
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
hopefully he didn't take your n7 into the sandbox like your poor camera lol :)
Got my n7 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.
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:


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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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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.
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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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.
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
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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I know this is an old thread, but have you looked into using this 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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