[G Tablet Q&A, Help & Troubleshooting] djab67:
GUIDE - Restore G Tablet after a Failed Recovery Mode "update.zip"

(continued from previous post)

APPENDIX

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M ) APX MODE AND NVFLASH TIPS

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Understanding APX Mode and how to use NVFLASH when in APX Mode was the most confusing piece for me to learn. It seems that others also struggle with the relationship between the two and how they are used.

APX Mode is a low level “on” state for devices with the tegra chips. I equate it to the “Bootloader” level on my HTC android phones. That comparison may not be entirely accurate because it seems APX Mode is at an even lower level than a Bootloader. The important point is both exist before any Recovery Mode (for example; Stock Recovery or ClockWorkmod Recovery).

NVFLASH is a program used to “flash” partitions (one or more) from a computer to the G Tablet when the gtablet is in APX Mode. NVFLASH can be used to flash just one or multiple partition images. NVFLASH should be run from a terminal session (command prompt in windows) since it needs various expressions and/or options defined when it is executed. The NVFLASH program can also be called from a script file (filename.sh) in Linux or a batch file (filename.bat) in windows. In the steps presented above, NVFLASH is run through script files.

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01 ) APX MODE TIPS

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Understanding APX Mode and how to use NVFLASH when in APX Mode was the most confusing piece for me to learn. It seems that others also struggle with the relationship between the two and how they are used.

To place the G Tablet in APX Mode I held down volume minus key and then pressed the power button for a second or two before releasing both. I did this with the G Tablet connected to my laptop via usb (mini usb port on the tablet and standard usb port on the laptop).

Validating a connection in APX Mode involved opening a terminal session (on the laptop) and typing the command lsusb. If the resulting output included a line containing “ID 0955:7820 NVidia Corp.”, then I knew I was connected to APX Mode with the laptop.

The G Tablet never gave me an indication that I was in APX Mode other than maybe a brief flash of light. Mostly I was staring at a blank screen and did not see any splash images. That is why I would validate the connection with the lsusb command.

Sometimes it would take a couple of attempts for me to get into APX Mode and establish a connection.. To set up a second attempt I would press the power button and then hold the volume minus and press power again. After each attempt I would check connection with lsusb.

IMPORTANT - An APX Mode connection is all that is needed to start the G Tablet restore steps. Recovery Mode (Stock or ClockWorkmod) and ADB are not needed to start. If the early APX Mode steps are successful then you will have access to those tools later on. When I messed up my G Tablet, the only thing I had to work with in the beginning was APX Mode and early on I didn't even know I had that. From my perspective all I had was a blank screen.

If APX Mode and connection to your PC cannot be obtained the first thing to do is check your drivers assuming your OS is windows. I never had a driver issue running Linux Mint Debian. You can find windows driver information at this site -Viewsonic GTablet For Dummies - nvflash.

If you think the drivers are ok and you still can't put the G Tablet in APX Mode, then you next step would be to research some “hard reset” options like “battery draining” and/or “unplugging the battery and shorting connections”. I am not addressing these methods in this post, but you can find techniques and information on this site and others with a little searching.

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02 ) NVFLASH TIPS

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NVFLASH is used when a G Tablet is in APX Mode. Do not use just any ROM download when using NVFLASH! It is important to make sure the ROM being used was set up for NVFLASH. When you extract a NVFLASH ROM download you will see the multiple files with the .img extension.

A “regular” ROM image usually just contains an “update.zip” file along with a “recovery” folder. Within the “recovery” folder there is usually a “command” file. A “regular” ROM image is applied using Recovery Mode, NOT nvflash. Again, make sure you are matching the downloads with the right application tools.

If you want to start learning about backing up with nvflash, here are a couple links to get your started:

[STICKY][GUIDE] Backup of your BCT AND Partition with NVFLASH on the gtab

Automated NVFlash backup for Linux

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N ) WINDOWS USER NOTES

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The major steps and sub-steps in this guide can also be executed from a windows computer. Here are the minor differences when using windows:

Download and use the contents of nvflash_windows_2010110500.zip instead of nvflash_linux_2010110500.tar.gz from [RECOVERY] nvflash FULL restore, using either 1.1 or 1.2 based images - [G-TABLET]. This is the same link provided earlier. Note that roebeet's post covers windows setup.

windows users will be using batch commands instead of shell scripts.

In one step above a script is edited. windows users will edit the batch (extension .bat) file instead. Be sure to use the right syntax for batch files, it is not the same as the script syntax illustrated in this guide. The downloaded batch file could be used as an example.

use the windows "command" window (aka; dos prompt, c:\> prompt) where ever a reference to "terminal" is made above.

some windows users report usb driver issues when trying to connect to a tablet in APX mode. Here is a place to begin searching for a solution if you have driver issues - Viewsonic GTablet For Dummies - nvflash

Here is a guide that may help windows users set up ADB - [STICKY][GUIDE] adb for your gtab (windows)