[FIXED] Help! My tablet is not booting anymore

[Arévalo Frutos]

I have changed some options in the bios that have made my tablet not boot any OS. I’ve disabled the usb devices so I can’t reset the bios settings, and I have changed the ACPI mode to the PCI mode in the eMMc config. I’ve tried to reset it by connecting the tablet in flash mode but it can’t flash the files becouse it does not detect the gpt partitions.

What can I do?

My tablet is the Chuwi Vi10 dual boot 32GB

PD: Sorry if I don’t write well in english, I’m spanish

Edit: Fixed. @Jonathan modified the TWRP recovery of @ImADev for make it restore the bios config when it was booted as droidboot and it worked for me.

[ImADev]

The combination of setting changes that you’ve made is really going to make this difficult for you. You’ll probably only be able to fix this by taking the tablet apart and flashing the BIOS with a programming tool.

You’ll probably need a CH341A programmer, a SOP8/SOIC8 clip + cable and maybe even a 1.8v adapter. It’ll depend on the type of BIOS chip that the Chuwi Vi10 uses. I can’t find any info on that though.

If you hold volume down as you power on the tablet can you access Android?

[Jonathan]

@ImADev, do you know any fastboot command to write UEFI NV variables? All of the settings he’s changed are in one 700 byte variable that simply needs to be reset (to values that I can probably provide).

@Arévalo, at some point you’ll need to know what version of BIOS you have, can you provide any information that you have on that please? Also this would be easily fixable from Windows so try the boot menu ImADev mentioned for both Android and Windows just in case.

[Arévalo Frutos]

@ImADev @blackbox thanks for your answer. The programmer chip you have mentioned will be my last option becouse I don’t want to disassemble it. I can change to Android or to Windows with volume buttons, but both take m o the bios shell.

@Jonathan I updated the bios with a file from this website, I’ve attached some photos for more information.

Attachments:

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[Jonathan]

@Arévalo, first and foremost please realise that you’ve screwed up badly and this won’t be simple 🙂

That said I have a plan, but really it needs an Android guy too.

I’ve done some experimenting on my device, as much as I can without getting into your position.

fastboot mode works when either the USB controller or port 0 is disabled.

Using Intel’s Manufacturing Flash tool I can boot a version of TWRP that’s been modified by ImADev to work with the Vi10.

Using a directory browser within TWRP (which works with the touchscreen) I’ve found the UEFI variable we need to set so it clearly supports the EFI service I need.

I think that it should be possible to unpack the TWRP recovery img and add something to reset the variable.

Also you have a BIOS version I can work with.

I’ll need to experminent some more before I know if my idea is feasible.

@ImADev, any thoughts you might have on this idea would be apreciated. I’m thinking that repacking TWRP with something to set the UEFI variable is clearly in your area? You  could probably also point me in the right direction with regards to removing the need for Intels Flash tool, i.e. just a way to boot TWRP with fastboot?

[ImADev]

@Jonathan
The fastboot commands are limited to Android only and AFAIK they can’t adjust the BIOS at all.

Within Android/TWRP you might see variables for USB related things, but none of them would adjust the BIOS settings. At best you could try to modify the kernel to force a parameter, but that might only get Android booting.

If he hadn’t of adjusted the ACPI mode then he could of just booted to Windows to clear the CMOS. Currently he’s pretty much screwed though as he can’t boot to Windows, he can’t boot from USB devices and the Android side of things can’t adjust the BIOS area.

Fastboot can’t boot directly into recovery by the way. It can flash the recovery image, but then you need to reboot into Android to reboot into recovery.

With the EFI shell it might be possible to force boot Windows if given the right commands.

https://software.intel.com/en-us/articles/uefi-shell
http://wiki.xkyle.com/EFI_Shell_Commands.html

@arevalo-frutos
What’s the ID written on the bottom left of your tablet?

If you’ve got a newer Vi10 then you wouldn’t of needed to change the BIOS. G1D_2165_206 is for older revisions of the Vi10, an update from G1D_2165_205. Newer Vi10 devices e.g. 221511 use J1D_S165C_206 instead.

[Arévalo Frutos]

@Jonathan @blackbox @ImADev thanks for yor help! I tested the tool to root the Chuwi Android and it launchs the CWM recovery as you say. It detects the partitions but

it can’t mount anything except the external sdcard. Where can I download the TWRP for test it?

@blackbox @ImADev my CPU ID : 30678

[Jonathan]

Sorry if I wasn’t clear enough I’m thinking of using the Linux filesystem interface to set the Setup variable.

I’m fairly sure I have booted TWRP without flashing though, I will need to pack some stuff together so we can test…

[ImADev]

@arevalo-frutos
I mean the code printed on the bottom of the tablet e.g. Vi10PQ64G221511.

[Jonathan]

I did however mistake the BIOS version for the one I have, that’ll be an extra headache but no matter…

[Arévalo Frutos]

@blackbox oh sorry, my code is: Vi10 Q32G22150504708

[ImADev]

You’ve got a May 2015 version. I’m not sure if that’s passes as a S165 or a S165C.

When you updated the BIOS did everything work or did something stop working and that’s why you changed the BIOS settings?

@Jonathan
I can’t say I’ve heard of that being done before. Which one either enables USB’s or changes the ACPI mode though? I don’t see either setting.

[Jonathan]

@ImADev, sorry I don’t understand what you are asking 🙂

“I can’t say I’ve heard of that being done before. Which one either enables USB’s or changes the ACPI mode though? I don’t see either setting.”

—-

An update on my experiments:

1. I can boot TWRP with the eMMC support disabled, it can’t see anything on the drive at all.
2. I can’t boot TWRP, or even get to the shell, with HW enumerating in PCI mode versus ACPI, this doesn’t bode well.
3. I can read the Setup NV variable from Android (after rooting), writing should be trivial and I will try and hack out something tomorrow.
4. I can’t read the Setup NV variable from TWRP, this could mean that the EFI variable support is broken or it could just be the way cp is reading the file.

I’m going to put together the Intel Flash setup that I’ve hacked up and see if the OP can boot TWRP, if not it’s game over unfortunately…

[Arévalo Frutos]

@blackbox I updated the bios after uprading to Windows 10 becouse I thought it was going to work better, after the update everything was ok. Some months later I started using Ubuntu with the mixed mode, but it was not detecting all the eMMc partitions, so bored I changed some options in the bios without think I could broke the os loaderand the usb keyboard.

[ImADev]

@Jonathan
I went to /sys/firmware/efi/vars/ on Android. It doesn’t contain any specific ACPI or USB folder, so I’m curious as to what directory you’re looking to modify?

You know, you could use hexdump to read the contents of your file and then use the terminal in TWRP?

hexdump /sys/firmware/efi/vars/folder_here/raw_var

echo -n -e "\x64\x65\x6d\x6f" > /sys/firmware/efi/vars/folder_here/raw_var

TWRP works with a mouse and keyboard to speed things up.

[Author]

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