[Transformer TF300T General] pjc21:
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

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.

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...

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.

Copy this blob file to your android-sdk/platform-tools folder

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

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"

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

Now boot device to bootloader (vol- & power) and connect to PC - fastboot will start automatically when connected to PC on the 4.2 bootloaders.

Open command prompt (run as admin) & check that PC can see your device OK.

fastboot devices

you should see device s/n here, if OK we can flash the system blob we put in the platform-tools folder

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.

When complete

fastboot reboot-bootloader

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.

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

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

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

When complete reboot to bootloader again.

fastboot reboot-bootloader

This time select the "RCK" icon and twrp recovery should boot up.

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

adb reboot-bootloader

Now select RCK and boot back to recovery, select and flash the CROMI 3.4.6.zip you put on your micro SD.

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

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.

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...

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.

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.

Copy this blob file to your android-sdk/platform-tools folder

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

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

Now boot tab to bootloader and connect to pc - fastboot will start automatically when connected to pc on the 4.2 bootloaders.

Check that pc can see your device ok

fastboot devices

you should see device s/n here, if ok we can flash the system blob we put in the platform-tools folder

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.

When complete

fastboot reboot-bootloader

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.

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

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

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

When complete reboot to bootloader again.

fastboot reboot-bootloader

This time select the "RCK" icon and twrp recovery should boot up.

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

adb reboot-bootloader

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.

When complete reboot system & again on boot you should see a blue progress bar, it will reboot once more and load up to android.

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.

Boot to twrp recovery and flash the CROMI 3.4.6 rom zip, reboot, Done.