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SHIELD RECOVERY IMAGE FLASHING INSTRUCTIONS
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To follow the instructions in this guide, you require the "adb" and "fastboot
utilities. These tools are provided as part of the Android SDK:
- http://developer.android.com/sdk/index.html

To setup the tools, follow one of Google's guides:
- http://developer.android.com/tools/help/adb.html#Enabling
- https://developers.google.com/cast/docs/android_tv#adb-usb

If you are running Windows and the standard Google adb USB driver does not
detect the SHIELD device, you can use NVIDIA's driver:
- https://developer.nvidia.com/gameworksdownload#?search=SHIELD%20Family%20Windows%20USB


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ENTERING FASTBOOT MODE
*****
To begin, connect your SHIELD via USB to the PC where you downloaded this recovery image.
- Insert a USB OTG cable and connect the other end to the host PC
- Setup adb using one of the guides above

Next, put your SHIELD into fastboot mode using one of the following methods:

Software Method:
- Boot the into Android
- Connect the device to the host PC
- Open terminal (on linux); command prompt (on windows).
- Type "adb reboot bootloader" at the prompt

Hardware Method:

- Boot the into Android
- Connect ThunderStrike(SHIELD Controller) to USB port near HDMI via USB cable.
- Power reset your device while holding A+B buttons on controller till you see bootloader menu.
- If the standard boot process starts, disconnect the power cable and repeat


OR

- Boot the into Android
- Connect USB keyboard to USB port near HDMI.
- Power reset your device while holding A+B buttons on keyboard till you see bootloader menu.
- You should now see the fastboot menu on the screen.
- If the standard boot process starts, disconnect the power cable and repeat
    

NOTE: You should leave the HDMI TV connected to SHIELD at all times.


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FASTBOOT MENU NAVIGATION
*****
Once in fastboot mode, 
- Navigate the menus using X or Y button on Controller. 
- Press A button on controller to select a menu item

OR
- Navigate the menus using arrow keys on USB keyboard.  
- Press ENTER on USB keyboard to select a menu item


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UNLOCKING THE BOOTLOADER
*****
Your SHIELD may have shipped with a locked bootloader. To update the device,
you must unlock the bootloader using the following command on the host PC:
- fastboot oem unlock

That command triggers a new page on the device headed '!!! READ THE FOLLOWING !!!'
- Read the warning on the screen
- To unlock the bootloader, select 'Confirm'

WARNING: Unlocking the bootloader securely formats the user data partition. This
process PERMANENTLY DELETES all data such as photos, music and downloads that
have previously been stored on the device.


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FLASHING THE DEVICE
*****
To flash the recovery image to your SHIELD, download and unpack the recovery
image package. From the unpack directory, execute the commands below for your
particular upgrade path.

If this is the first time you have done this procedure, you must unlock the
bootloader (see above step).

*****
* SHIELD UNITS WITH ANDROID LOLLIPOP OR LOWER
*
If your SHIELD device OS is currently running Android Lollipop or lower
(i.e. the Android version is less than 6.0) or you are unsure of the OS
version, follow these intructions:

*** Prerequisites:
    1.  Ensure that the bootloader is unlocked (see above step)
    2.  Ensure USB debugging is enabled and adb is working (when not
        in fastboot mode)

*** Flashing instructions:
    1.  Execute these commands IN ORDER on the host PC:

        adb reboot bootloader
        fastboot flash staging blob
        fastboot flash boot boot.img
        fastboot reboot
        adb wait-for-device
        adb reboot bootloader
        fastboot flash recovery recovery.img
        fastboot flash system system.img
        fastboot flash vendor vendor.img
        fastboot reboot

    NOTE: If the "adb wait-for-device" step does not complete within
    5 minutes, you can try re-entering fastboot mode using the
    "Hardware Method" given in the "ENTERING FASTBOOT MODE" step above. Then
    execute the rest of the commands after "adb reboot bootloader".

*****
* SHIELD UNITS WITH ANDROID MARSHMALLOW OR NEWER
*
If you are CERTAIN that your SHIELD device OS is currently running Android
Marshmallow or newer (i.e. the Android version is 6.0 or greater), follow
these intructions:

*** Prerequisites:
    1.  Ensure that the bootloader is unlocked (see above step)

*** Flashing instructions:
    1.  Execute these commands on the host PC:

        fastboot flash staging blob
        fastboot flash boot boot.img
        fastboot flash recovery recovery.img
        fastboot flash system system.img
        fastboot flash vendor vendor.img
        fastboot reboot