[HOW-TO] Upgrade or Downgrade to any stock JB Firmware

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pjc21

Senior Member
Mar 3, 2012
509
647
Melbourne
After almost a full day of flashing I now have a 100% successful method of flashing any stock JB Firmware
With this method I have been able to successfully flash any stock JB Firmware from 10.4.2.9 all the way through to 10.6.1.27.5 without issue.
unfortunately you can not go back to ICS bootloader or firmware (there is a signature mismatch issue here).


Try this at your own risk, I will not be responsible for a bricked device.

Recommend doing NVFlash first so your tablet is Unbrickable
NVFlash for ICS bootloader
NVFlash for JB bootloader


Warning:
If you flash an incorrect recovery to a 4.2 bootloader there is about a 90% chance that fastboot flash commands will now just freeze the tablet - When you attempt to flash via fastboot everything will seem to go ok on the command prompt but you will not see the blue progress bar on the tablet when flashing & the reboot command will not reboot the tablet after the flash command & nothing will have flashed to the tablet.

If this is the case try this solution.


Please read below for how to check your bootloader version and confirm your flashing the correct recovery.


Requirements:
  • Must be unlocked (Method 1 seems to work fine for locked devices but must be unlocked for Method 2 to flash custom recovery).
  • Must have working fastboot
  • Working adb in recovery (optional). I use adb in this method for rebooting but this can be done manually with vol- & power.

Always make a backup first.

Files Needed:
Download the stock JB firmware you wish to flash from either the Asus website or from the Index thread here, be sure to download the correct SKU version you wish to use On your tablet you can check what SKU your using by going to settings>about tablet, scroll down to build number and you can see SKU version..

If using method 2 download the TWRP recovery you require, Here is a link to the TWRP thread. When you download a version of TWRP it will have a name like "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - You can rename to something shorter for flashing if you like, I rename like so "twrp-2.5.0.0-4.2.blob".

What recovery to flash for bootloader version: example for TF300T model:

Check & confirm what bootloader your on - boot to bootloader menu (vol- & power) and look at the text in top left, your bootloader version number is there.

JB 4.1 firmwares

  • If current bootloader = 10.4.2.9 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
  • If current bootloader = 10.4.2.13 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
  • If current bootloader = 10.4.2.17 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
  • If current bootloader = 10.4.2.18 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
  • If current bootloader = 10.4.2.20 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM

JB 4.2 Firmwares

  • If current bootloader = 10.6.1.8 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.4.4.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device. Also flashing 2.5.0.0-tf300t-4.2 on the 10.6.1.8 bootloader results in a split-screen issue.
  • If current bootloader = 10.6.1.15.3 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.
  • If current bootloader = 10.6.1.27.1 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.
  • If current bootloader = 10.6.1.27.5 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.


My Notes about TWRP 2.4.4.0-4.2:
TWRP 2.4.4.0-4.2 will not mount my sandisk 64gb micro SDXC UHS-1 class 10 card, but previous versions of TWRP have no issue. I believe this is a UHS-1 issue. TWRP 2.5.0.0-4.2 has fixed this bug and and can now mount 64gb micro SDXC UHS-1 class 10 card again.


Method 1

  1. Unzip the firmware zip you downloaded, there will be another zip file inside.

    Example:
    Lets say you choose WW 10.4.2.20 firmware. (same method apply's for any firmware version and SKU you choose - US, WW, JP, TW, CN)
    [*]Unzip "WW_epaduser_10_4_2_20_UpdateLauncher.zip"and you will find another zip inside "WW_epad-user-10.4.2.20.zip".
    [*]Now unzip the WW_epad-user-10.4.2.20.zip and you will find a "blob" file.
    [*]Now copy the blob file to your android-sdk\platform-tools folder.


    Now to the flashing:
  2. With your device loaded in android go to settings, developer options and make sure they are on & usb debugging is on.
    [*]Plug device into PC with usb cable & boot to fastboot.


    Using adb commands

    Open command prompt (run as admin) & cd to you android-sdk\platform-tools folder.
    Check your PC can see your device
    Code:
    adb devices
    You should get a list with you device s/n, if not then adb is not setup.
    Next
    Code:
    adb reboot-bootloader

    or

    Manually boot to fastboot

    Hold vol- & power button to boot to bootloader then connect to PC.

    Fastboot will start automatically when connected to PC on the 4.2 bootloaders. On 4.1 bootloaders you will need to select the usb icon using vol- to highlight the usb icon and vol+ to select.


    Note:
    In bootloader NEVER select the Wipe Data icon or you will brick.

  3. Once in fastboot open command prompt & cd to you android-sdk\platform-tools folder and type command
    Code:
    fastboot devices
    and again here you should get a list with you device s/n, if not then fastboot is not setup.

    [*]If OK we can now flash the system blob we put in the platform-tools folder

    Code:
    fastboot -i 0x0b05 flash staging blob

    This will take about 10 minutes to send & write system, you will see a progress bar on device when system is writing.

    [*]When complete

    Code:
    fastboot reboot

This method should work fine but have found that sometimes the device will get stuck at the boot animation, if this happens method 2 works fine every time.

Method 2

  1. Unzip the firmware zip you downloaded, there will be another zip file inside.

    Example:
    Lets say you choose WW 10.4.2.20 firmware. (same method applys for any firmware version and SKU you choose - US, WW, JP, TW, CN)
    [*]Unzip "WW_epaduser_10_4_2_20_UpdateLauncher.zip"and you will find another zip inside "WW_epad-user-10.4.2.20.zip".

    [*]Place a copy of the WW_epad-user-10.4.2.20.zip on your microSD card.
    [*]Now on PC unzip the WW_epad-user-10.4.2.20.zip and you will find a "blob" file.
    [*]Now copy the blob file to your android-sdk\platform-tools folder.

    [*]Now copy the "twrp-version.blob" file you downloaded to your android-sdk\platform-tools folder.
    --Make sure you have the correct twrp version for the firmware your flashing.


    Now to the flashing:
  2. With your device loaded in android go to settings, developer options and make sure they are on & usb debugging is on.
    [*]Plug device into PC with usb cable & boot to fastboot.


    Using adb commands

    Open command prompt (run as admin) & cd to you android-sdk\platform-tools folder.
    Check your PC can see your device
    Code:
    adb devices
    You should get a list with you device s/n, if not then adb is not setup.
    Next
    Code:
    adb reboot-bootloader

    Manually boot to fastboot

    Hold vol- & power button to boot to bootloader then connect to PC

    Fastboot will start automatically when connected to PC on the 4.2 bootloaders. On 4.1 bootloaders you will need to select the usb icon using vol- to highlight usb icon and vol+ to select.


    Note:
    In bootloader NEVER select the Wipe Data icon or you will brick.

  3. Once in fastboot open command prompt & cd to you android-sdk\platform-tools folder and type command.
    Code:
    fastboot devices
    and again here you should get a list with you device s/n, if not then fastboot is not setup.

    [*]If OK we can now flash the system blob we put in the platform-tools folder.

    Code:
    fastboot -i 0x0b05 flash staging blob

    This will take about 10 minutes to send & write system, you will see a progress bar on device when system is writing.

    [*]Once this has completed type in the command prompt.
    Code:
    fastboot reboot-bootloader

    You can now check that your bootloader has upgraded/downgraded, look at the text in the top left of the bootloader screen and make sure it's changed to the firmware version you just flashed.

    [*]Now again depending on the bootloader version go to fastboot.

    Next
    [*]In the below command I am using "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" for JB firmware 10.4.2.20, and shortened the name "twrp-JB.blob" so just change command according to TWRP version needed.
    Code:
    fastboot -i 0x0b05 flash recovery twrp-JB.blob
    [*]Once this has completed type in the command prompt.
    Code:
    fastboot reboot-bootloader

    [*]Now this time in bootloader select the "RCK" icon to enter twrp recovery.
    [*]In twrp recovery select "Wipe".
    [*]Here I do a complete wipe (cache, Dalvik cache, Factory Reset, System, Internal Storage & Format Data) I don't believe Internal Storage & Data Format are necessary but I like a full clean flash.

    [*]Once you have done full wipe type in command prompt.
    Code:
    adb reboot-bootloader

    or manually reboot to bootloader, hold vol- and power button.

    [*]Now again in bootloader select the "RCK" icon to enter twrp recovery.
    [*]In twrp recovery disconnect your device usb cable from PC.

    [*]Select "Install" & select the firmware zip you copied to your external sd card and slide to flash/install.

    [*]Once completed reboot, you will get message at top of recovery saying there is no OS installed are you sure you want to reboot - slide to confirm yes, another message will popup asking if you want root permissions installed - I select NO "Do not install" you can probably select yes here if you want twrp to root.

    The device will reboot, you'll see a progress bar as the signature is being matched, it will reboot again when done.
    Now device will boot with the stock JB bootloader & firmware you have chosen.

    Done.


You can now flash twrp, then flash any custom rom for that firmware.



As I have said I have done this with all stock WW JB firmware available and can confirm that the bootloader does change and system will boot and run without any issues. But try at own risk.

Firmware I have done this with: Only tried with WW SKU
  • 10.6.1.27.5
  • 10.6.1.27.1
  • 10.6.1.15.3
  • 10.6.1.8
  • 10.4.2.20
  • 10.4.2.18
  • 10.4.2.17
  • 10.4.2.13
  • 10.4.2.9

More Info:
Downgrading from CROMi-X back to CROMi-3.4.6

Upgrading from ICS to JB

If you this information is helpful please hit the thanks button.
 
Last edited:

wetbiker7

Senior Member
Aug 12, 2011
1,607
1,694
Nice work and thanks for sharing it PJC21. Looks like you've got quite a bit of time invested in this info. :thumbup:

Sent from my LG-LG855 using Xparent SkyBlue Tapatalk 2
 

jimpmc

Senior Member
Sep 6, 2011
76
19
Thank you for the detailed information. Couldn't one just flash the stock .zip file from TWRP, reboot, reinstall TWRP recovery from fastboot and then wipe in TWRP as you would do when upgrading? I have done that between JB releases before, but I guess the bootloader didn't change.
 

pjc21

Senior Member
Mar 3, 2012
509
647
Melbourne
Thank you for the detailed information. Couldn't one just flash the stock .zip file from TWRP, reboot, reinstall TWRP recovery from fastboot and then wipe in TWRP as you would do when upgrading? I have done that between JB releases before, but I guess the bootloader didn't change.

Yeah quite possibly, I didn't even think to try it that way :laugh:

However if just flashing the system blob via fastboot then rebooting, my devices will get to the boot animation screen and just sit there.

I do prefer being on the correct bootloader before flashing the firmware though and this way allows for that.
 
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tobdaryl

Senior Member
May 7, 2010
1,277
474
Maybe consider making this two parts.
1. with twrp recovery installed
2. with stock recovery installed
Good info and needed!

Note: I should have added with twrp, fastboot, or adb to flash I always loose root and data. With stock if I am using the same version or anything numerically higher I keep root and data but going to a lower numeric I loose root and data.
I hope this is understandable.
 
Last edited:

Q-Logic

Senior Member
Jul 28, 2011
86
15
I can confirm that this method 101 % works. :good:
I have migrated from custom ROM 4.2.1 to factory 4.2.1.
After final reboot I lost root, but rooting afterwards gave me rooted factory 4.2.1. No problems at all.
Thanks for this.
 

Keshukas

Senior Member
Aug 22, 2010
151
50
I can confirm that this method 101 % works. :good:
I have migrated from custom ROM 4.2.1 to factory 4.2.1.
After final reboot I lost root, but rooting afterwards gave me rooted factory 4.2.1. No problems at all.
Thanks for this.

+1 works

Sent from my GT-I9100 using xda app-developers app
 

funnel71

Senior Member
Jan 24, 2011
959
209
OK, I have a question. I see this works with full ROMs from Asus, good. What about TWRP backups?

So, before I upgraded to 4.2.1, I took a TWRP backup of 4.1.1 latest v20 build. If I restored that backup via TWRP, would it work? Would the bootloader revert to the older one (with the USB icon)? My backup did include the boot partition, but I didn't know if this would brick the device.

Sent from my ASUS Transformer Pad TF300T using Tapatalk 2
 

MrsColumbo

Member
Jun 29, 2012
31
10
Just to make sure ...

Have you actually downgraded from 4.2.1 to 4.1.1?

I'm on 4.2.1 (10.6.1.8; Energy Rom) at the moment and eager to browse all those nice custom roms that are based on 10.4.x.x. like cm 10.1 & co.

Since the 4.2 upgrade rearranged the file system i'm afraid of messing it up when reverting to pre-multiuser-versions ...

Also i'd love to have this nvflash brickproof thingie ...

You think I could give this a go?
 

Q-Logic

Senior Member
Jul 28, 2011
86
15
Have you actually downgraded from 4.2.1 to 4.1.1?

I'm on 4.2.1 (10.6.1.8; Energy Rom) at the moment and eager to browse all those nice custom roms that are based on 10.4.x.x. like cm 10.1 & co.

Since the 4.2 upgrade rearranged the file system i'm afraid of messing it up when reverting to pre-multiuser-versions ...

Also i'd love to have this nvflash brickproof thingie ...

You think I could give this a go?

To be honest - I'm not sure, I didn't downgrade, let pjc21 say did he. I would be afraid to do mess with file system just like you.
But I would be interested to try this if his downgrading method works.
 
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pjc21

Senior Member
Mar 3, 2012
509
647
Melbourne
OK, I have a question. I see this works with full ROMs from Asus, good. What about TWRP backups?

So, before I upgraded to 4.2.1, I took a TWRP backup of 4.1.1 latest v20 build. If I restored that backup via TWRP, would it work? Would the bootloader revert to the older one (with the USB icon)? My backup did include the boot partition, but I didn't know if this would brick the device.

Sent from my ASUS Transformer Pad TF300T using Tapatalk 2

I'm not sure here, but would think no as the new update has a different file system arrangement. I myself would not try this as I really have no idea what would happen.
 

pjc21

Senior Member
Mar 3, 2012
509
647
Melbourne
Have you actually downgraded from 4.2.1 to 4.1.1?

I'm on 4.2.1 (10.6.1.8; Energy Rom) at the moment and eager to browse all those nice custom roms that are based on 10.4.x.x. like cm 10.1 & co.

Since the 4.2 upgrade rearranged the file system i'm afraid of messing it up when reverting to pre-multiuser-versions ...

Also i'd love to have this nvflash brickproof thingie ...

You think I could give this a go?

Yes I have downgraded from 4.2.1 (10.6.1.8) to 4.1.1 (10.4.2.20) and I have also downgraded through all the JB firmware back to the first JB firmware that came out 10.2.4.9 -28/08/2012- not that many people would want to go back that far but I was attempting to go all the way back to an ICS bootloader & firmware so I could access NVflash and become brickproof as my tab came with JB pre-loaded. When attempting to go from a JB bootloader & firmware to an ICS one there is a signature mismatch which I have not looked into as yet and am not sure it would even be possible to modify this to get a match. I will have a look when I get the time and look at the differences between the JB & ICS signatures to see if it might be possible to modify these.
 
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MrsColumbo

Member
Jun 29, 2012
31
10
Works fine

Yes I have downgraded from 4.2.1 (10.6.1.8) to 4.1.1 (10.4.2.20) and I have also downgraded through all the JB firmware back to the first JB firmware that came out 10.2.4.9 -28/08/2012- not that many people would want to go back that far but I was attempting to go all the way back to an ICS bootloader & firmware so I could access NVflash and become brickproof as my tab came with JB pre-loaded. When attempting to go from a JB bootloader & firmware to an ICS one there is a signature mismatch which I have not looked into as yet and am not sure it would even be possible to modify this to get a match. I will have a look when I get the time and look at the differences between the JB & ICS signatures to see if it might be possible to modify these.

Witch much satisfaction I can confirm this working. Had to sideload the update zip, though, 'cause I forgot to copy it to my external micro sd card. in the course I ****ed up the update (progress indicator not progressing, so i did a vol-+power-reset, subsequently rom did not load), but adb-d recovery again, inserted micro sd and did the update (downdate) to 10.4.2.20. running cm 10.1 nightly now.

Yeah, this brickproof mod sounds really good. I wouldn't want to miss up on jb's smoothness, though. IMHO JB and ICS are worlds apart. Maybe those guys give it a go with a 4.2-brickproof-mod one fine day :)

Thanks pjc21 for this outstandig work. This is what Android OS is about: being able to explore all possibilities of a fine piece of hardware you actually own instead of being led on a leash by a corporation. :good::good::good:
 

treo4life

Senior Member
Dec 27, 2007
447
105
Atlanta, Ga.
This worked pretty easy, returning from 4.2.1 ( 10.6.1.8) I flashed the 4.1.1 (10.4.2.20) blob through fast boot,then flashed twrp 2.3.3.0 in fast boot, rebooted into recovery restored my 4.1.1 backup and all is well.
 
Last edited:

wetbiker7

Senior Member
Aug 12, 2011
1,607
1,694
Yes I have downgraded from 4.2.1 (10.6.1.8) to 4.1.1 (10.4.2.20) and I have also downgraded through all the JB firmware back to the first JB firmware that came out 10.2.4.9 -28/08/2012- not that many people would want to go back that far but I was attempting to go all the way back to an ICS bootloader & firmware so I could access NVflash and become brickproof as my tab came with JB pre-loaded. When attempting to go from a JB bootloader & firmware to an ICS one there is a signature mismatch which I have not looked into as yet and am not sure it would even be possible to modify this to get a match. I will have a look when I get the time and look at the differences between the JB & ICS signatures to see if it might be possible to modify these.

Please update us on your progress. Everything I've read says that going back to ICS for NVFlash cannot be done if the tablet came with JB. Thanks.

Sent from my LG-LG855 using Xparent SkyBlue Tapatalk 2
 

wetbiker7

Senior Member
Aug 12, 2011
1,607
1,694
He stated you cannot go back to ICS in the first post,, but you can switch JB firmware pretty easy.

Exactly. But........ he also said he was going to try and modify the signatures to see if he can get them to match. If he can succeed, it will be a huge breakthrough.

Sent from my LG-LG855 using Xparent SkyBlue Tapatalk 2
 

treo4life

Senior Member
Dec 27, 2007
447
105
Atlanta, Ga.
That's true, don't know if he is going to try to tackle that one though.. would be nice to have the option...

Sent from my EVO using xda premium
 

ntunit

Senior Member
Jul 28, 2012
59
12
I just received my new tablet ... Need to downgrade to 4.1.1 to be able to run AOSP Rom.

Thanks for the procedure. I will give it a try.
 

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  • 57
    After almost a full day of flashing I now have a 100% successful method of flashing any stock JB Firmware
    With this method I have been able to successfully flash any stock JB Firmware from 10.4.2.9 all the way through to 10.6.1.27.5 without issue.
    unfortunately you can not go back to ICS bootloader or firmware (there is a signature mismatch issue here).


    Try this at your own risk, I will not be responsible for a bricked device.

    Recommend doing NVFlash first so your tablet is Unbrickable
    NVFlash for ICS bootloader
    NVFlash for JB bootloader


    Warning:
    If you flash an incorrect recovery to a 4.2 bootloader there is about a 90% chance that fastboot flash commands will now just freeze the tablet - When you attempt to flash via fastboot everything will seem to go ok on the command prompt but you will not see the blue progress bar on the tablet when flashing & the reboot command will not reboot the tablet after the flash command & nothing will have flashed to the tablet.

    If this is the case try this solution.


    Please read below for how to check your bootloader version and confirm your flashing the correct recovery.


    Requirements:
    • Must be unlocked (Method 1 seems to work fine for locked devices but must be unlocked for Method 2 to flash custom recovery).
    • Must have working fastboot
    • Working adb in recovery (optional). I use adb in this method for rebooting but this can be done manually with vol- & power.

    Always make a backup first.

    Files Needed:
    Download the stock JB firmware you wish to flash from either the Asus website or from the Index thread here, be sure to download the correct SKU version you wish to use On your tablet you can check what SKU your using by going to settings>about tablet, scroll down to build number and you can see SKU version..

    If using method 2 download the TWRP recovery you require, Here is a link to the TWRP thread. When you download a version of TWRP it will have a name like "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - You can rename to something shorter for flashing if you like, I rename like so "twrp-2.5.0.0-4.2.blob".

    What recovery to flash for bootloader version: example for TF300T model:

    Check & confirm what bootloader your on - boot to bootloader menu (vol- & power) and look at the text in top left, your bootloader version number is there.

    JB 4.1 firmwares

    • If current bootloader = 10.4.2.9 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
    • If current bootloader = 10.4.2.13 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
    • If current bootloader = 10.4.2.17 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
    • If current bootloader = 10.4.2.18 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM
    • If current bootloader = 10.4.2.20 - JB 4.1 - recovery to flash = TWRP "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" or CWM

    JB 4.2 Firmwares

    • If current bootloader = 10.6.1.8 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.4.4.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device. Also flashing 2.5.0.0-tf300t-4.2 on the 10.6.1.8 bootloader results in a split-screen issue.
    • If current bootloader = 10.6.1.15.3 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.
    • If current bootloader = 10.6.1.27.1 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.
    • If current bootloader = 10.6.1.27.5 - JB 4.2 - recovery to flash = ONLY TWRP "openrecovery-twrp-2.5.0.0-tf300t-4.2.blob" - flashing a non-4.2 version of TWRP or any version of CWM will brick device.


    My Notes about TWRP 2.4.4.0-4.2:
    TWRP 2.4.4.0-4.2 will not mount my sandisk 64gb micro SDXC UHS-1 class 10 card, but previous versions of TWRP have no issue. I believe this is a UHS-1 issue. TWRP 2.5.0.0-4.2 has fixed this bug and and can now mount 64gb micro SDXC UHS-1 class 10 card again.


    Method 1

    1. Unzip the firmware zip you downloaded, there will be another zip file inside.

      Example:
      Lets say you choose WW 10.4.2.20 firmware. (same method apply's for any firmware version and SKU you choose - US, WW, JP, TW, CN)
      [*]Unzip "WW_epaduser_10_4_2_20_UpdateLauncher.zip"and you will find another zip inside "WW_epad-user-10.4.2.20.zip".
      [*]Now unzip the WW_epad-user-10.4.2.20.zip and you will find a "blob" file.
      [*]Now copy the blob file to your android-sdk\platform-tools folder.


      Now to the flashing:
    2. With your device loaded in android go to settings, developer options and make sure they are on & usb debugging is on.
      [*]Plug device into PC with usb cable & boot to fastboot.


      Using adb commands

      Open command prompt (run as admin) & cd to you android-sdk\platform-tools folder.
      Check your PC can see your device
      Code:
      adb devices
      You should get a list with you device s/n, if not then adb is not setup.
      Next
      Code:
      adb reboot-bootloader

      or

      Manually boot to fastboot

      Hold vol- & power button to boot to bootloader then connect to PC.

      Fastboot will start automatically when connected to PC on the 4.2 bootloaders. On 4.1 bootloaders you will need to select the usb icon using vol- to highlight the usb icon and vol+ to select.


      Note:
      In bootloader NEVER select the Wipe Data icon or you will brick.

    3. Once in fastboot open command prompt & cd to you android-sdk\platform-tools folder and type command
      Code:
      fastboot devices
      and again here you should get a list with you device s/n, if not then fastboot is not setup.

      [*]If OK we can now flash the system blob we put in the platform-tools folder

      Code:
      fastboot -i 0x0b05 flash staging blob

      This will take about 10 minutes to send & write system, you will see a progress bar on device when system is writing.

      [*]When complete

      Code:
      fastboot reboot

    This method should work fine but have found that sometimes the device will get stuck at the boot animation, if this happens method 2 works fine every time.

    Method 2

    1. Unzip the firmware zip you downloaded, there will be another zip file inside.

      Example:
      Lets say you choose WW 10.4.2.20 firmware. (same method applys for any firmware version and SKU you choose - US, WW, JP, TW, CN)
      [*]Unzip "WW_epaduser_10_4_2_20_UpdateLauncher.zip"and you will find another zip inside "WW_epad-user-10.4.2.20.zip".

      [*]Place a copy of the WW_epad-user-10.4.2.20.zip on your microSD card.
      [*]Now on PC unzip the WW_epad-user-10.4.2.20.zip and you will find a "blob" file.
      [*]Now copy the blob file to your android-sdk\platform-tools folder.

      [*]Now copy the "twrp-version.blob" file you downloaded to your android-sdk\platform-tools folder.
      --Make sure you have the correct twrp version for the firmware your flashing.


      Now to the flashing:
    2. With your device loaded in android go to settings, developer options and make sure they are on & usb debugging is on.
      [*]Plug device into PC with usb cable & boot to fastboot.


      Using adb commands

      Open command prompt (run as admin) & cd to you android-sdk\platform-tools folder.
      Check your PC can see your device
      Code:
      adb devices
      You should get a list with you device s/n, if not then adb is not setup.
      Next
      Code:
      adb reboot-bootloader

      Manually boot to fastboot

      Hold vol- & power button to boot to bootloader then connect to PC

      Fastboot will start automatically when connected to PC on the 4.2 bootloaders. On 4.1 bootloaders you will need to select the usb icon using vol- to highlight usb icon and vol+ to select.


      Note:
      In bootloader NEVER select the Wipe Data icon or you will brick.

    3. Once in fastboot open command prompt & cd to you android-sdk\platform-tools folder and type command.
      Code:
      fastboot devices
      and again here you should get a list with you device s/n, if not then fastboot is not setup.

      [*]If OK we can now flash the system blob we put in the platform-tools folder.

      Code:
      fastboot -i 0x0b05 flash staging blob

      This will take about 10 minutes to send & write system, you will see a progress bar on device when system is writing.

      [*]Once this has completed type in the command prompt.
      Code:
      fastboot reboot-bootloader

      You can now check that your bootloader has upgraded/downgraded, look at the text in the top left of the bootloader screen and make sure it's changed to the firmware version you just flashed.

      [*]Now again depending on the bootloader version go to fastboot.

      Next
      [*]In the below command I am using "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" for JB firmware 10.4.2.20, and shortened the name "twrp-JB.blob" so just change command according to TWRP version needed.
      Code:
      fastboot -i 0x0b05 flash recovery twrp-JB.blob
      [*]Once this has completed type in the command prompt.
      Code:
      fastboot reboot-bootloader

      [*]Now this time in bootloader select the "RCK" icon to enter twrp recovery.
      [*]In twrp recovery select "Wipe".
      [*]Here I do a complete wipe (cache, Dalvik cache, Factory Reset, System, Internal Storage & Format Data) I don't believe Internal Storage & Data Format are necessary but I like a full clean flash.

      [*]Once you have done full wipe type in command prompt.
      Code:
      adb reboot-bootloader

      or manually reboot to bootloader, hold vol- and power button.

      [*]Now again in bootloader select the "RCK" icon to enter twrp recovery.
      [*]In twrp recovery disconnect your device usb cable from PC.

      [*]Select "Install" & select the firmware zip you copied to your external sd card and slide to flash/install.

      [*]Once completed reboot, you will get message at top of recovery saying there is no OS installed are you sure you want to reboot - slide to confirm yes, another message will popup asking if you want root permissions installed - I select NO "Do not install" you can probably select yes here if you want twrp to root.

      The device will reboot, you'll see a progress bar as the signature is being matched, it will reboot again when done.
      Now device will boot with the stock JB bootloader & firmware you have chosen.

      Done.


    You can now flash twrp, then flash any custom rom for that firmware.



    As I have said I have done this with all stock WW JB firmware available and can confirm that the bootloader does change and system will boot and run without any issues. But try at own risk.

    Firmware I have done this with: Only tried with WW SKU
    • 10.6.1.27.5
    • 10.6.1.27.1
    • 10.6.1.15.3
    • 10.6.1.8
    • 10.4.2.20
    • 10.4.2.18
    • 10.4.2.17
    • 10.4.2.13
    • 10.4.2.9

    More Info:
    Downgrading from CROMi-X back to CROMi-3.4.6

    Upgrading from ICS to JB

    If you this information is helpful please hit the thanks button.
    6
    Downgrading from CROMi-X back to CROMi-3.4.6

    Here are two methods I use for downgrading from CROMi-X back to CROMI (4.2 bootloader back to 4.1 bootloader).

    Method 1

    1. Download the 10.4.2.20 firmware zip - All stock asus firmware zips can be found here - On your tablet you can check what SKU your using by going to settings>about tablet, scroll down to build number and you can see SKU version.
    2. Once downloaded unzip xx_epaduser_10_4_2_20_UpdateLauncher.zip to a folder & you should find a second zip file, xx_epad-user-10.4.2.20.zip - xx is the SKU version your using, ie WW/US...
    3. Unzip the xx_epad-user-10.4.2.20.zip and you should find a blob file - this file is the 10.4.2.20 system, stock recovery, kernel & bootloader all rolled into a one blob file.
    4. Copy this blob file to your android-sdk/platform-tools folder
    5. The version of twrp you need for 10.4.2.20 would be "2.5.0.0-tf300t-JB.blob" NOT THE -4.2 versions, these are for the 4.2 bootloaders which are firmwares 10.6.1.8 / 10.6.1.15.3 / 10.6.1.27.1
    6. So download "openrecovery-twrp-2.5.0.0-tf300t-JB.blob" and also put this in android-sdk/platform-tools folder - you can rename it to something shorter if you want, like "twrp-JB.blob"
    7. Download CROMI 3.4.6.zip and copy to your microSD card.
      CleanROM 3.4.6 Inheritance ODEX_Signed.zip
      CleanROM 3.4.6 Inheritance DEODEX_Signed.zip
    8. Now boot device to bootloader (vol- & power) and connect to PC - fastboot will start automatically when connected to PC on the 4.2 bootloaders.
    9. Open command prompt (run as admin) & check that PC can see your device OK.

      Code:
      fastboot devices
    10. you should see device s/n here, if OK we can flash the system blob we put in the platform-tools folder

      Code:
      fastboot -i 0x0b05 flash staging blob

      This will take about 10 minutes, it will send file then write file and you should a blue progress bar on tab when it starts to write.

    11. When complete

      Code:
      fastboot reboot-bootloader
    12. You should now check that your bootloader has downgraded, look at the text in the top left of the bootloader screen and make sure it's now has 10.4.2.20 - you should now also have 4 icons RCK (recovery), android (cold boot), usb (fastboot) & wipe-data - don't use the wipe data icon in bootloader - it seems to brick tabs.

    13. So from bootloader screen go to fastboot (vol- to the usb icon - then vol+ to select) and flash the twrp recovery.

      Code:
      fastboot -i 0x0b05 flash recovery twrp-JB.blob

      again here you should see a blue progress bar on your tab.

    14. When complete reboot to bootloader again.

      Code:
      fastboot reboot-bootloader
    15. This time select the "RCK" icon and twrp recovery should boot up.

    16. I do a full wipe here in recovery then reboot back to recovery again as I also format data in recovery.

      Code:
      adb reboot-bootloader
    17. Now select RCK and boot back to recovery, select and flash the CROMI 3.4.6.zip you put on your micro SD.
    18. When complete reboot system, Done.


    This method should work fine but have found that sometimes the device will get stuck at the boot animation, if this happens method 2 works fine every time.


    Method 2

    1. Download the 10.4.2.20 firmware zip - All stock asus firmware zips can be found here - On your tablet you can check what SKU your using by going to settings>about tablet, scroll down to build number and you can see SKU version.
    2. Once downloaded unzip xx_epaduser_10_4_2_20_UpdateLauncher.zip to a folder & you should find a second zip file, xx_epad-user-10.4.2.20.zip - xx is the SKU version your using, ie WW/US...
    3. Here I put a copy of the xx_epad-user-10.4.2.20.zip on my micro SD card. You can also download & copy the CROMI 3.4.6 zip to your microSD.
    4. On pc unzip the xx_epad-user-10.4.2.20.zip and you should find a blob file - this file is the 10.4.2.20 system, stock recovery, kernel & bootloader all rolled into a one blob file.
    5. Copy this blob file to your android-sdk/platform-tools folder
    6. The version of twrp you need for 10.4.2.20 would be "2.5.0.0-tf300t-JB.blob" NOT THE -4.2 versions, these are for the 4.2 bootloaders which are firmwares 10.6.1.8 & 10.6.1.15.3
    7. So download "twrp-2.5.0.0-tf300t-JB.blob" and also put this in android-sdk/platform-tools folder - you can rename it to something shorter if you want, like twrp-JB.blob
    8. Now boot tab to bootloader and connect to pc - fastboot will start automatically when connected to pc on the 4.2 bootloaders.
    9. Check that pc can see your device ok

      Code:
      fastboot devices
    10. you should see device s/n here, if ok we can flash the system blob we put in the platform-tools folder

      Code:
      fastboot -i 0x0b05 flash staging blob

      This will take about 10 minutes, it will send file then write file and you should a blue progress bar on tab when it starts to write.

    11. When complete

      Code:
      fastboot reboot-bootloader
    12. You should now check that your bootloader has downgraded, look at the text in the top left of the bootloader screen and make sure it's now has 10.4.2.20 - you should now also have 4 icons RCK (recovery), android (cold boot), usb (fastboot) & wipe-data - don't use the wipe data icon in bootloader - it seems to brick tabs.

    13. So from bootloader screen go to fastboot (vol- to the usb icon - then vol+ to select) and flash the twrp recovery.

      Code:
      fastboot -i 0x0b05 flash recovery twrp-JB.blob

      again here you should see a blue progress bar on your tab.

    14. When complete reboot to bootloader again.

      Code:
      fastboot reboot-bootloader
    15. This time select the "RCK" icon and twrp recovery should boot up.

    16. I do a full wipe here in recovery then reboot back to recovery again as I also format data in recovery.

      Code:
      adb reboot-bootloader
    17. Now select RCK and boot back to recovery, select and flash the xx_epad-user-10.4.2.20.zip you put on your micro SD.
    18. When complete reboot system & again on boot you should see a blue progress bar, it will reboot once more and load up to android.
    19. You have now downgraded to stock 10.4.2.20 - you will also have stock recovery so just fastboot flash twrp again, step 13-14.
    20. Boot to twrp recovery and flash the CROMI 3.4.6 rom zip, reboot, Done.
    1
    Thank you for the detailed information. Couldn't one just flash the stock .zip file from TWRP, reboot, reinstall TWRP recovery from fastboot and then wipe in TWRP as you would do when upgrading? I have done that between JB releases before, but I guess the bootloader didn't change.

    Yeah quite possibly, I didn't even think to try it that way :laugh:

    However if just flashing the system blob via fastboot then rebooting, my devices will get to the boot animation screen and just sit there.

    I do prefer being on the correct bootloader before flashing the firmware though and this way allows for that.
    1
    Have you actually downgraded from 4.2.1 to 4.1.1?

    I'm on 4.2.1 (10.6.1.8; Energy Rom) at the moment and eager to browse all those nice custom roms that are based on 10.4.x.x. like cm 10.1 & co.

    Since the 4.2 upgrade rearranged the file system i'm afraid of messing it up when reverting to pre-multiuser-versions ...

    Also i'd love to have this nvflash brickproof thingie ...

    You think I could give this a go?

    To be honest - I'm not sure, I didn't downgrade, let pjc21 say did he. I would be afraid to do mess with file system just like you.
    But I would be interested to try this if his downgrading method works.
    1
    Hi, sorry to revive an old post.
    I have a TF300T with 4.2.1 stock and no unlocked bootloader. I've downloaded v8 bootloader and it gives me "network connectivity issue" every time.
    I'm currently trying to figure this out with Asus Support, but since I've seen this had something to do with the Device Tracker database and it seems Device Tracker doesn't exist anymore... then my guess is v8 won't work.

    So I'm wondering if v7 would work even if it says on Asus Support that it's only for 4.0... I've seen a youtube video of a guy unlocking and installing twrp on a 4.2.1 with v7. Is this a bad idea? Otherwise, could I use the fastboot method to flash in a 4.0 ROM and try v7 and once unlocked, upgrade to 4.2.1 again?

    Hope I get an answer. Thanks!

    Your problem is well known and widely discussed on several forums. To your understanding please Google it firstly if you want to unlock your devise. Here we go:

    1. As far as I know V8 does not install at all anymore. V7 will install if you allow "less secure apps" in your Google account settings. On the web - not your Google account on the tablet!

    2. Delete the Google account from the tablet (Settings > Accounts), then run the tool again,

    3. If that doesn't do it, do a factory reset from Settings, reboot and during the initial setup establish a WiFi connection but skip the google account setup, then run the tool.

    This can be a 5 Minute operation that goes without a hitch or a very frustrating experience with lots of error messages. There is no definite rhyme or reason for this. For some people it works like a charm, for others it works after 15, 25 or 55 attempts, for some never....
    To check finally if you are unlocked, boot the tablet and read the tiny script in the left corner above. It should say: “The device is unlocked”.