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Nexus 7 internal sd card.

12th December 2012, 04:35 AM   |  #221  
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Quote:
Originally Posted by jb user

Having managed to download the schematics and the Tegra 3 data sheets, and then spending the last 3 hours studying them, I have discovered the following:

Using the OTG connector for Internal storage would only be possible with some form of physical switching of the data and ID lines, the connector is hardwired to both the processor and the charging circuit. While there is a data device connected, it is unlikely that the charge control circuitry would allow high current charging to take place through the OTG connector even with a custom kernel, it may however be possible to trickle / maintain the battery while using the port. There is no electronic reason (I can see) why high current charging can't take place using the dock connector while the OTG connector is in use.

The Tegra 3 processor has 4 available USB ports, there is only mention of three being used on the schematics. USB1 is directly connected to the OTG connector, USB2 is used for the 3G module, USB3 was intended to be used for the side dock (POGO) connector (but this has not been implemented).

There is a connection to the Tegra's UART through the headphone connector, it appears to be a debug connection, and I doubt it will be of any real use.

I think our best hope of internal USB will be from the USB2, it should be easy to find on a 3G equipped unit, less so on a WiFi only (like mine) version. Dependant on soldering skills, it could be possible to break into the data lines on a 3G unit and install a small hub.

When my eBay unit arrives, I will get onto it!!

Will you be able to share the Tegra3 data sheets? Are they hardware or software data sheets?
It would be great if the unused USB ports came out to some of the test points (small copper colored dots on the PCB used during bed of nails PCB testing at the factory). Typically, when ports like these are not used, they are tied high or low. When tied high, it's usually through a pullup resistor. If someone has the programmers reference and can write a small pgm to check the USB ports to see if they're high or low, that would be a start.


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12th December 2012, 02:32 PM   |  #222  
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Search for 'me370t.PDF' its dropbox'd by someone, comes up as the second link for me


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Last edited by funkysam78; 12th December 2012 at 02:40 PM.
12th December 2012, 10:19 PM   |  #223  
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Quote:
Originally Posted by bigbop

Will you be able to share the Tegra3 data sheets? Are they hardware or software data sheets?
It would be great if the unused USB ports came out to some of the test points (small copper colored dots on the PCB used during bed of nails PCB testing at the factory). Typically, when ports like these are not used, they are tied high or low. When tied high, it's usually through a pullup resistor. If someone has the programmers reference and can write a small pgm to check the USB ports to see if they're high or low, that would be a start.


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The processor data sheets are available on the NVIDIA developer website, you can gain access by creating an account then requesting. The hardware information is limited, it is aimed at software rather than hardware development.

I'm good with hardware mods, but rely on others more knowledgeable to deal with the software 'tweaks' needed to make things work. What I could do with is a way of viewing what connected USB devices the processor can see (something as simple as windows "view devices by connection" would do). I have access to the test gear needed to find the data lines.
14th December 2012, 05:25 AM   |  #224  
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Quote:
Originally Posted by jb user

The processor data sheets are available on the NVIDIA developer website, you can gain access by creating an account then requesting. The hardware information is limited, it is aimed at software rather than hardware development.

I'm good with hardware mods, but rely on others more knowledgeable to deal with the software 'tweaks' needed to make things work. What I could do with is a way of viewing what connected USB devices the processor can see (something as simple as windows "view devices by connection" would do). I have access to the test gear needed to find the data lines.

It seems you're doing the same as I am here. Another h/w geek. You might want to look at XDA user Chainfire's apps. One is Stickmount and the other is a USB diagnostic app.

What test equipment do you have to find data lines that might not even be hooked up to the outside world? Personally, I thought someone could write a small app that would toggle the extra usb/sd/hdmi data lines at a specific frequency and then use a small antenna probe and spectrum analyzer to probe the motherboard to find the line(s) with the signal.


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15th February 2013, 05:44 AM   |  #225  
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I definitely will be looking at the schematic tomorrow. thanks for the info
18th April 2013, 10:06 AM   |  #226  
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Might I also suggest to look for any SPI interface or GPIO's. SPI wouldn't be the fastest possible way to access a SD-Card but it's simple. The protocol itself could also be implemented with a simple driver over GPIO.
19th April 2013, 11:41 PM   |  #227  
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A little off topic and sorry but where would the JTAG connections be on this board since it been taken apart maybe someone would know? Which connector or pins on the board?

I want to test to see if I can recover a completely bricked bootloader through JTAG if the connections are easy?

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22nd April 2013, 02:57 AM   |  #228  
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The JTAG pins are located on the unused con1 connector beside the speaker connector on the other side of the board. Check out the schematics for the pin out. Schematics links are in some of the various threads. Search for me370t and schematic.

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22nd August 2013, 07:26 PM   |  #229  
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Switchmode regulators
Quote:
Originally Posted by ED2O9

Just a quick heads up... the two red leads coming off of the battery aren't 7.4V. It's a 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

No it's not. If you use a more modern inverting (switchmode) regulator it'll work just fine (they dissipate a lot less power than linear regulators so the extra cost is usually worth it on battery-driven kit.)

Search on farnell.com for "Linear Regulator Drop In Replacement". Farnell and RS have other (smaller) ones available too.

if you can find an internal usb port then 5V should be obtainable from that anyway.

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