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Offline Phrozenbit

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A23 based Denver TAD-90032MK2 tablet recovery methods.
« on: August 24, 2015, 04:25:07 PM »
A23 based Denver TAD-90032MK2 tablet recovery methods.

This is a piece of an article I wrote on my blog that should help you restore the Denver TAD-90032MK2, and took the time to properly format it for easy reading on this forum. You can read the full article here.

Here's how to fix the tablet. It took me a week to fix it and I share this here because nobody else has to go through the same difficult and tedious recovery process as I have. This how-to is divided in two parts, the first part is for those who were wise enough to create a full partition backup which can be used to recover the tablet and the second part is for those who want to recover their tablet using the stock firmware.

Part 1: Using your partition dumps, or mine if you prefer so.

This method is recommended is you have made backups of your partitions. You can fully recover your tablet and recover all your installed apps and other files. You may also use mine, if for some reasone flashing the stock firmware doesn't work.

There are a couple of things you need first. Your tablet has to be booted with a firmware that comes really close to your original firmware. It's likely some hardware doesn't work at all, but all you need is an ADB  shell. You need to have the ADB driver set up correctly, you need adb.exe and fastboot.exe. You also need to have root access on your tablet. You need to have your raw partition dumps and your partition table ready. If you choose this route I will assume you're familiar with the above mentioned things. If not I recommend reading this forum thread by HardcoreHacker to set up the Android debug bridge. If you'd like you can download everything you need from my DropBox account, unpack everything before using though.You'll also need a good amount of time and patience for this one, it may be quite tedious if you're not used to this kind of tinkering. Get the downloadable stuff here:


First, make sure your tablet is running, has the USB debugging is ebabled ( which is default on most close firmwares that work on this particular tablet ) and that ADB is recognizing your device. Open up a dos prompt by pressing and holding the windows flag button and pressing 'R'. In the window that pops up type 'cmd'. When the dos prompt has opened navigate to the folder which contain the adb.exe and fastboot.exe and type the following code:

Code: [Select]
adb devices
It should, provided you've got the ADB USB driver set up correctly, show your device in the list.

Next, fire up a shell on your tablet using the adb, enter the following command to get there:

Code: [Select]
adb shell
You should now have a root shell on your tablet. What you're going to do is remount the /system partition so you've got write permissions, you'll need that because you're going to recover the system partition with your backup copy. Enter the following command to do so:

Code: [Select]
mount -o remount,rw /system
You shuld now fire up another dos-prompt using the windows flag key and 'R', and you should navigate to the folder containing adb.exe and fastboot.exe again. You should also copy your raw backup of the system partition to the folder containing the adb.exe and fastboot.exe.

Once you've got everything in place, enter the following command in the second dos-prompt to push the backup to the tablet:

Code: [Select]
adb push system.img /mnt/sdcard/
This pushes the backup to the /mnt/sdcard/ user storage partition, and it may take up to 5 minutes depending on your system. Now, in the first dos-prompt, the one with the shell on the tablet, you should enter the following command to write your system.img backup to the partition:

Code: [Select]
dd if=/mnt/sdcard/system.img of=/dev/block/nandd bs=4096
This process may also take up to 10 minutes depending on how much data you've got in the system partition. The next steps are really crucial to this recovery process because there's a certain checksum based backup and restore going on with android you don't want doing it's thing right now. The only thing you can now do is get out of the shell because you've written e complete new /system partition. Because of that nothing works with regards to shell commands so just type exit and hit enter. In the first command prompt you're now back in the dos emulator. You're now going to boot your tablet into it's bootloader, and perform some flashing using fastboot.exe. This is the most important procedure you must follow this to the letter. In the first dos-prompt enter the following command to reboot your device into it's bootloader:

Code: [Select]
adb reboot bootloader
You're device should now be waiting for instructions for fastboot, which is exactly what we need now. What we are going to do next is erase every partition on the device except for the system partition. There are partitions on this tablet that contain backups of /system, /boot, and /boot-resource that are created upon first boot. Whenever you reboot your tablet, android checks these partitions and compare the data in the backup partitions ( /misc and /databk ) with the boot and system partitions to see if something has changed. If something has changed android restores the data from these backup partitions. Extremely secure but also extremely annoying if something is wrong with hardware configuration for example. To circumvent this we're going to just erase the backup partitions and leave them empty at first boot. We're also going to make sure the tablet recieves it's instructions and data by using the USB vendor ID, in case fastboot doesn't recognize your tablet (like it didn't in my case). You'll be sending the instructions and data blindly so make sure you don't send it to other USB devices! First you need to get rid of the boot partition, enter the following command in your second dos-prompt:

Code: [Select]
fastboot -i 0x1f3a erase boot
Then erase the boot-resource partition:

Code: [Select]
fastboot -i 0x1f3a erase boot-resource
Erase the env parition:

Code: [Select]
fastboot -i 0x1f3a erase env
Get rid of the randomness in the misc partition:

Code: [Select]
fastboot -i 0x1f3a erase misc
Erase the databk partition:

Code: [Select]
fastboot -i 0x1f3a erase databk
You might as well just erase data, cache and recovery as well to get a clean start. Erase the recovery partition:

Code: [Select]
fastboot -i 0x1f3a erase recovery
Erase the Data partition:

Code: [Select]
fastboot -i 0x1f3a erase data
And finally erase the cache partition:

Code: [Select]
fastboot -i 0x1f3a erase cache
Obviously you can't boot the device now becasue you don't have a bootloader and recovery partition at this point so make sure you copy the boot.img, boot-resource.img, recovery.img and env.img in the folder that contain the adb.exe and fastboot.exe file. If you've done that it's time to flash the most important partitions, namely the boot, boot-resource, env and recovery partitions. We've already got the system partition, the cache and data partitions will be re-created at first boot and we absolutely want the databk and misc partitions to remain empty. So first we flash the boot image using the following command in your second dos-prompt:

Code: [Select]
fastboot -i 0x1f3a flash boot boot.img
This should restore your boot partition, second get the boot-resource back on there:

Code: [Select]
fastboot -i 0x1f3a flash boot-resource bootre-source.img
This restores your hadware configuration and other boot related thingy-mabobs. Next get your env partition on there:

Code: [Select]
fastboot -i 0x1f3a flash env env.img
I don't exactly know where this partition comes to use during tablet operation but according to the internet it's U-boot's environment. Lastly get your recovery partition restored. Although not that important if you know how to recover your tablet using this method it's just nice to have around for completion sake:

Code: [Select]
fastboot -i 0x1f3a flash recovery recovery.img
That's about it, as stated before cache and data will be created at first boot, and we've already got our system partition so let's reboot and fire up your tablet by typing the following command:

Code: [Select]
fastboot -i 0x1f3a reboot
This should reboot your device. If all went well, and you have recieved no errors what so ever you're device should now be fully restored even with your device driver configuration and installed apps. Now never mess around with your tablet again!

Part two: Recoverying the tablet with the stock firmware

I've contacted Denver support and requested the stock firmware. It took a short while but eventually, to my surprise, they responded and sent me a WeTransfer link with the original firmware. At this point I already fixed my tablet using the above mentioned method but it's still very usefull for people who brick their tablet and want to fix it. Using this method you don't restore every installed app and its data, it's restored to factory settings, it will be as brand spanking new again. This tutorial also isn't as lengthy as the previous one so don't be afraid of reading a wall of text again just follow the instructions well.

You need a couple of things to get this done. It is VERY important to have a charged battery or to have it hooked up to the AC charger when you flash your device. You'll need the stock firmware and the PhoenixSuit tool you can download from my DropBox account:


First, unpack everything and install the PhoenixSuit program on your PC. Then press and hold the power button for 10 seconds, get a clock or just steadily count to 10. It's important that your device is really off. Make sure it's NOT connected to the USB port of your PC at this point.

After installing PhoenixSuit, fire it up using the icon on your desktop and press the "Firmware" tab on the top of the program.

Next, select the image by clicking the blue "Image" button to the right of the box that says "Please Select the Image File First". Navigate to the directory to which you've downloaded the firmware to, select the image and click "open".

Now click the big green "Upgrade" button and click though the first couple of dialogs with "yes" and "ok" until you see a dialog that reads "Do Mandatory Upgrade?" with a set of instructions on how to enable hardware flashing mode of your tablet. DO NOT PRESS the "ok" button just now.

Get your Denver tablet, plug the USB cable into your PC, and follow the following instructions to the letter.

  • Press the Volume + button and hold it
  • Get your USB cable and plug it in
  • While still holding the Volume + button, sequentially press and release the Power On button three times and then let go of everything.

PhoenixSuit should respond immediately and it will ask you if you want to do a mandatory upgrade and a mandatory format. Choose "yes" if those dialogs apear. Let PhoenisSuit do it's thing for 7 to 10 minutes. When it's done flashing, your tablet should restart and boot.

Congratulations, your tablet has been un-bricked and is now fully functional again.
« Last Edit: August 24, 2015, 07:38:01 PM by HardcoreHacker »
~Phrozen

Offline Stephan

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Re: A23 based Denver TAD-90032MK2 tablet recovery methods.
« Reply #1 on: August 25, 2015, 11:52:12 AM »
Hey PhrozenBit,

congratulations on your success unbricking the A23! Thank you very much for this nice tutorial which is well written!

Interesting, "fastboot -i 0x1f3a flash env env.img", I wonder if there's a way to read/dump the env usig fastboot.

Too bad I never had a A23 :( :( :( reading all this makes me wonder many things and a lot of that I would like to try out :)

HcH

Offline Vicenter

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Re: A23 based Denver TAD-90032MK2 tablet recovery methods.
« Reply #2 on: April 18, 2018, 05:27:38 AM »
For the reason I came in this time, I needed some useful information.