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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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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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Discussion Starter · #64 ·
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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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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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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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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Discussion Starter · #68 ·
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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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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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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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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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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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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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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@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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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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Discussion Starter · #78 ·
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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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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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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