[Upgrading, Modifying and Unlocking] twrock:
“Unofficial” Guide to Flashing the Official Jiayu G2S ROM

Disclaimer: I’m just one guy who got this to work after a lot of trial and error. I’m only telling you how I did it. I don’t claim it will work for you. I don’t guarantee you won’t brick your phone by following these instructions. And you should understand that if you don’t bother to read carefully and do exactly what I say, you really can brick your phone. Also, it seems there has been an upgrade to some of the components in later versions of the phone released in March 2013, and you will want to verify which version of the phone you have before installing any roms. You should be able to check the rom build information for the date on your particular phone. This guide only describes how to flash the official rom from Jiayu for the G2S. If you intend to install some other third-party rom, please follow that rom builder's instructions.​

Pre-requisites:

You need a PC running Microsoft Windows 2000 or higher.

If you haven’t previously installed msxml 6.0 and .net Framework 4.0 or higher on you Windows PC, do so first. Get them directly from Microsoft. (I assume you know how to search.)

Download the following:

Latest Jiayu G2S ROM update; the rom I installed was the G2s_20130109-104044 stock rom: http://pan.baidu.com/share/link?shareid=157669&uk=839171988 (Note: the build number of the ROM after installation is: G2S 20130108-104044; don't be confused by the name of the file.) Use Google Translate if you need to see which button to push to start the download. Also note that there is a newer official rom for newer versions of the phone. The rom date is 20130306. I don't know what happens if you install the newer version on an older phone.

This zip file contains the Android USB driver, VCom drivers, SP Flash Tool, and a document of these instructions (ReadMe.doc): http://www.mediafire.com/?tc4q3wy5eabowhf

Unzip the files you downloaded and move/copy folders and files where they need to go:

Within the rom zip that you downloaded from the Baidu website, you can find the \G2s_20130109-104044 sub-folder. This folder contains the actual rom files (14 files). Move this entire folder onto your desktop. The reason for doing this is that there are folders within the zip file whose names contain characters that your version of Windows might not be able to read, even if you can see them in Windows Explorer (the filemanager). This will cause you trouble when you try to flash the rom.

After unzipping the driver and flash tool zip file, you will find the \USB-VCOM-Drivers folder with \INF and \SYS sub-folders. In the \INF folder there are three other sub-folders: \ 2K_XP_COM, \Vista, and \Win7.

Copy the \INF\cdc-acm.inf file into your C:\Windows\inf folder. (You may have to give permission to do this.)

Based on your version of Windows (2K-XP, Vista, Win7, 32-bit or 64-bit), locate the one correct usb2ser_????.inf file and copy it to your C:\Windows\inf folder. (You may have to give permission to do this.)

Copy both the \SYS\androidusb.sys and \SYS\usbser.sys into your C:\Windows\System32\driver folder. (You may have to give permission to do this.)

Install the drivers:

Plug your phone into your computer with a USB cable. If you had not previously installed the drivers, the system will start trying to install them.

If the system asks you to choose to install the drivers, click on “install the software automatically” and proceed.

If system is unsuccessful in locating and installing the drivers, you can try to go back and locate the drivers yourself by pointing to the individual files, but this should not happen if you properly copied the drivers over to your C:\Windows system folders.

BACKUP YOUR DATA NOW!

Proceeding beyond this point is going to mean that EVERYTHING on you phone is going to be deleted and a new system will replace it.

You have been warned!

Warning!

Attempting to install a rom that does not use the correct “scatter” file (see description below) will brick your phone. Don’t do it. If you aren’t sure a rom is made for your phone, don’t attempt to install it.

Install the updated ROM:

1.	Turn off your phone, open the back, and remove the battery.

2.	Plug your USB cable into your PC and phone. If your PC attempts to install drivers, let it finish.

3.	Unplug your phone from the cable.

4.	Start the SP Flash Tool program by clicking on the Flash_tool.exe file. If you get a security warning, allow it to run.

5.	Click on the “Scatter-loading” button on the right side.

6.	Browse to your \Desktop\G2s_20130109-104044 folder and choose the MT6577_Android_scatter_emmc.txt file. All other files will be chosen automatically.

7.	Click on the “Firmware -> Upgrade” button.

8.	Plug your USB cable firmly into the phone. The Flash Tool will automatically start flashing your new rom. Wait for it to finish and show you the green circle.

9.	Unplug your phone from the cable.

Rebooting the phone:

1.	Install your battery.

2.	Very carefully, without touching the screen, push the power button.

3.	Do not touch the phone as it boots!

4.	After it has completed booting, you may again use your phone normally.