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  1. #1
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    Bruteforce eMMC Flash Hacking of the Acer A200 - Thoughts and proposal

    Introduction:
    I am newbie on this site, but I am an Engineer & not a complete novice when it comes to tablet hacking. However, I didn't think to "backup" whatever was on the damned thing before I totally killed the bootloader (not that it would really have made any difference in this case).

    Circumstances that led to my issue:
    I have completely "hard-bricked" a A200 that was originally "soft-bricked". It was "soft-bricked" in the sense that I could not mount, delete, or format the /DATA partition no matter what I had attempted. (Yeah, tried Fastboot userdata and with the -w context, and also that Wipe utiility ,etc.) Finally, I ended up trying to revert back to a stock ROM using the CWM Recovery. Btw, I had unlocked the bootloader when I first installed the CWM. As the tablet updated to the stock ROM, I saw something flash on the screen for a couple of seconds that stated ".blob failed" in red before all went dark.

    Current state:
    I've lost all ADB and Fastboot ability, and am left only with the APX mode. I've researched this method for a few days. While it seems to be a viable approach for the A500; Unfortunately, it is close to impossible (maybe is indeed impossible) to recover the A200 tablet by way of nvFlash unless you are able to calculate a magic number (SBK) with a unique CPUID for your particular tablet. Correct me if I am wrong, I don't think anyone was able to ever revive an A200 through APX? (If I am incorrect, please do call me out on that statement, and then help me out with the nvFlash process for the A200.)

    Proposal:
    Determine the pin-out of the eMMC device, and find all the required connections on the board, and wire them directly to a modified USB SDCARD reader. Finally, write the image directly to the eMMC device. Keep in mind that I have already successfully hacked the Kindlefire2 with this exact same method by writing a raw image directly to the eMMC flash. The Kindlefire processor did not allow writing an image via the OMAP for the same reason that the A200 Tegra 2 does not allow it; simple because of the magic number is not unique to the CPU. This brute force should work on the A200. I still have the modified USB SDCARD reader that I'd used on the Kindlefire 2.

    Unknowns:
    I haven't yet opened up the hood of the tablet.

    Requirements:
    I need a detailed good partition table, the eMMC Flash used on the tablet, and I need a raw image (.bin) to burn.

    Any comments are appreciated. Please post a good partition table, the eMMC part used on the mobo, and/or upload a binary for the A200 (if one exists). If I can't get a raw binary, I will need a good A200 motherboard for which to experiment. Does anyone have a busted A200 laying around that has a good motherboard that they are willing to part with?

    UPDATE1: I found the eMMC devices that are used on the tablets "Hard Disk Drive Interface." In fact, I found the complete field service manual for the A200.

    16GB: Kingston KE44B-26BN/16GB OR SanDisk SDIN5C1-16G
    8GB: Kingston KE44B-26BN/8GB OR SanDisk SDIN5C2-8G


    UPDATE2: I found this in one of the stock ROM scripts: package_extract_file("bootloader.blob","/dev/block/mmcblk0p5"); At least now I (think that I) have the bootloader if I have a partition structure left on the eMMC to look at. I still would prefer just a raw .bin or .img file of the eMMC to just write. Anyone have it?

    UPDATE3: Found Blobtools to extract .blob files. Found stock OS as UPDATE.ZIP wit the bootloader.blob file for the Acer A200. I will try extract the contents of this .blob file. Also found NVFLASH utility for another Tegra 250 tablet (Viewsonic Gtablet) that works directly with APX mode. I will see if this yields anything before I rip the tablet open. I will have to edit the gtablet.cfg file for the Acer A200 partition structure & figure out how to make a .bct file too. Anyone have a detailed printout of the partition table with address location & size parameters? Still looking for a raw image (.img) of the A200 FLASH or even a bootloader.bin, anyone???

    UPDATE4: Purchased a cheap 16GB A200 motherboard for $10 on E-Bay of unknown state. Hopefully will boot. Will plug in the 12V adapter and the USB, and then see if the the PC recognizes the board. If it's a good board, I might just try to wire in my FLASH reader to the EMMC, and read the raw image. After I replace the bricked mobo with the (hopefully) good one, I will try to write the image to it. Will update this at some point.

    {{{ Lots of reads on this topic.....but no comments, no help, and no suggestions though.....disappointing }}}

    Thanks,
    Kevin
    Last edited by kevin_d; 03-25-2015 at 10:47 PM.

  2. #2
    Iconia Lurker
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    whats the update on this?

  3. #3
    Iconia Lurker
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    Sbk and cpuid backup

    hi, i found a backup of my cpuid and sbk, can i do anything with those?
    a74500942dff317
    CPUID

    0xCF2D1100 0xCB95D506 0x0BF93304 0xF6302103
    SBK
    Iconia a200 32gb wifi:

    Rom: stock (ics)
    Kernel: Onyx oc 1.5Ghz
    Recovery: TWRP

  4. #4
    Iconia Lurker
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    Sorry for necro

    Hey Kevin, been a few years and I'm not generally a fan of necroing old threads, but I found my old a200 in a box this weekend and it is in virtually the same state. I was just wondering if you had any luck resolving the issues?


 

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