***** THE FOLLOWING WILL NOT UNBRICK AN ALREADY HARDBRICKED NEXUS 7.
This procedure is preemptive... you will need to have run it BEFORE being bricked.
This has been available on XDA for about a fortnight now, so I thought I would bring it to the attention of everybody here.
I had no involvement in the development of the following method. This is purely a FYI post/thread.
As is known, the Nexus 7 (2012) has a critical software component known as the bootloader.
A common cause of what are called hardbricks are (usually, but not always) as a result of a corrupted or erased bootloader. To put it simply, and succinctly...
** A DEAD BOOTLOADER = A DEAD NEXUS 7 **
The Nexus 7, with a dead or corrupted bootloader, will by default, boot into APX mode, with the expectation that :::?somebody?::: with expert knowledge, and the appropriate software will then nvFlash a new bootloader.
Unfortunately however, due to the unique crypto-signed nature of the bootloader, there is no universal software solution available that can be distributed for everybody to use.
The bootloader partition (and the data it contains) is unique to each specific Nexus 7.
Fortunately however, the brainy guys over at Flatline, have found a way of generating unique 'blobs' for each Nexus 7. These are then used, in conjunction with nvFlash, to resurrect a hardbricked Nexus 7.
However, these 'blobs' MUST be created BEFORE any such 'hardbricking' and are NOT transferable from one Nexus 7 to another.
They are YOUR 'blobs', and YOU must take personal responsibility for them.
Having run this procedure myself, I have made 9 backup copies of my own 'blobs'- some on local storage (laptop, USB memory stick, a copy on my Nexus 7)... and some on Cloud storage (DropBox, Box, etc.)
The instructions and software by which these 'blobs' are generated are available in the following two links...
The Flatline software downloads and full instructions are available here...
The XDA discussion thread is here...
This is a potentially risky procedure, as it involves fastboot flashing a specially modified version of the CWM Custom Recovery. This Custom Recovery will then, in turn, flash a specially modified version of the v4.13 bootloader.
Using the Custom Recovery (and 'wheelie'), you then generate your 'blobs'. There are a few other things to do after that... but that's pretty much it.
Upon completion of the entire procedure, after you've successfully created your 'blobs', you'll need to fastboot flash back to the stock (ie., standard) unmodified bootloader.
And then, optionally fastboot flash back to whatever Custom Recovery (CWM or TWRP) you had installed prior to the commencement of this procedure.
It is an involved procedure, requiring multiple reboots... but not, I feel, unduly complicated. It requires complete adherence to the written instructions given in the first link above, without deviation.
With that in mind though, it's pretty straightforward to acquire the necessary files that would render your Nexus 7 'unbrickable'.
WARNING: To anybody thinking of doing this, please be aware of the advanced nature of this subject. This is a potentially dangerous procedure, that could hardbrick your tablet.
If you've only ever used Toolkits before, to Root or to flash Custom ROMs and are not familiar with command line interfaces, such as fastboot and ADB require, I would strongly recommend you avoid it.