[K4NT, Help needed] Bricked, but visible as USB HID

[umbertone]

Hi, folks!

I've applied jailbreak to my Kindle 4 NT as described in this post: https://www.mobileread.com/forums/sho...&postcount=240, I also installed localized firmware update.

The device has been working for a few days with no problems. Then at some point it didn't turn on. After trying and leaving it for a while, it turned on again. After couple days the problem returned. Now it cannot turn on, I also don't see it as USB host. Nevertheless, it appears as USB HID in the Windows Device Manager.

I've read that it's possible to connect to Kindle using such mode, but have no idea how to do it and how to restore the firmware or whatever's needed to bring it back to life.

I will appreciate any help. Thanks!

[geekmaster]

I have this problem now too. It happened when I pressed the 5-way left key at "to continue - FW LEFT" message in the "Disable Diagnostics" menu of the K4NT diagnostics mode. Now even the power LED will not come on except while plugged into a usb power source. If connected to a computer is shows up as USB HID.

[hostar]

Ok, this is for Touch model, but maybe it could work.
https://wiki.mobileread.com/wiki/Kind...ownloader_mode

[geekmaster]

Originally Posted by hostar

Ok, this is for Touch model, but maybe it could work.
https://wiki.mobileread.com/wiki/Kind...ownloader_mode

I tried that last night. It says it successfully downloads code to the k4nt successfully executes it. After doing the exec, the USB port resets and I have to reattach it to my windows VM in Virtualbox. It makes sense that the usb would reset because the "random" code I sent to the kindle was just a copy of the freescale tool (wrong cpu). The tool docs show sending a file called uboot.bin.

I think that my k4nt "brick" problem was caused by a bug in the k4nt diagnostics mode "disable diagnostics" menu code. It normally erases /mnt/us/ENABLE_DIAGS and then it calls "idme" to change boot mode from diag to main. But idme can ALSO change the serial number and the board ID, with different parameters. I think that when the bad code failed to erase the missing ENABLE_DIAGS, it called idme with bad parameters that made it change my serial number and board ID to "1". And uboot does not know how to initialize RAM for a device with board ID "1".

I should have exited diags with a restart instead of disable diags.

Is there any recovery from a corrupted board ID? I do not know memory layout or device port mapping, so USB/HID mode is not much use to me at this time unless I compile my own uboot.The only thing I can think is to run a modified uboot in RAM that treats board ID 1 as a k4nt. Where do I find the k4nt uboot source code?

Does anybody have other ideas?

[eureka]

Originally Posted by geekmaster

Where do I find the k4nt uboot source code?

I guess, you should look at Kindle source code provided by Amazon. I don't know if there is u-boot source code for Kindle in appropriate source code tarball, but it is so for Kindle Touch.

[geekmaster]

More info (including serial port output) here:
https://www.mobileread.com/forums/sho...3&postcount=45

[geekmaster]

Actually, diags has a different menu item for changing board id and serial number. Perhaps when the code broke from a missing ENABLE_DIAGS file, it jumped into the code that changes the board id and serial number, without requesting user input.

I really wish that uboot was a little smarter and if bad board id, it would give you a serial port option to enter a board id, or choose which board type to initialize from a menu. Of course, the uboot INSTALLED on a k4nt should DEFAULT to initializing it as a k4nt. IMHO...

Even better if diags did not shoot itself in the head when it gets confused...

EDIT: No time to deal with this now. It has the serial port brought out through a slightly lifted spot under the flexible back cover. Later, I will try patched uboot that defaults to hardware init for "k4nt" board type. I did notice that the gpl download .tar.gz files for 4.0 and 4.0.1 have different file names, but both have same size and same md5sum. I just ordered another k4nt so I can continue testing my code instead of wasting time trying to debrick this one. Anybody want to buy a bricked k4nt (serial number and board id both "1"), with serial port?

[geekmaster]

Well... I learned one thing at least:

If you export the USB drive from diagnostics mode, or access it with SSH in diagnostics mode, you should not delete /mnt/us/ENABLE_DIAGS and then select "Disable Diagnostics" from the exit menu.

It appears that this can corrupt your serial number and board ID information so that the generic u-boot logic cannot decide how to initialize the hardware. This is what you might call "bricking your kindle".

EDIT: I am now loading and running custom u-boot boot loader code in my bricked k4nt RAM using USB HID mode, thanks to the efforts of yifanlu. Now I need to patch the boot loader to force a valid board ID, so it can continue the boot process.