[Android Head-Units] threadreaper:
So you followed a bad tutorial, or lost power during a flash, or formatted your unit for some reason and now you have a unit that seems mostly unresponsive. All hope may not be lost. You do have a backup, right??

If you don't have your own backup, you may be able to find one online somewhere that will work, but be aware that not all 8227L units are the same, and not every ROM dump you find online is going to work. At any rate, the issue is beyond the scope of this tutorial, so we'll proceed assuming you either have your own backup or have located a compatible one. I'm also going to assume that you have SP-Flashtool and have been able to use it, as it's fairly hard to end up with a bricked unit without using SP-Flashtool to begin with.

There are two different types of backup that can be relied on in this situation. The first, and probably more reliable backup format is a ROM dump from SP-Flashtool, consisting of 3 files, BOOT_1, BOOT_2, and EMMC_USER. They may be named something different. If SP-Flashtool's automatically suggested names were used, they could be named ROM_0, ROM_1 and ROM_2, in which case you'll need to pay attention to the file sizes. The other type is a group of many files, containing backups of the individual partitions, usually named boot.img, recovery.img, system.img, userdata.img, etc. In either case, you will also require a suitable scatter file, which you should have with your backup.

You're going to need to access the "test point" on your unit in order to flash your backup if you have flashed the wrong pre-loader or formatted the pre-loader partition. There is a chunk of read-only memory on the board containing the factory preloader, and that's what we'll be accessing to pull this off.

For information on disassembling your unit and accessing the test point, see my tutorial here on unlocking the bootloader.

Determine the process for reloading your backup based on the type of backup that you have and the state your system is in by reading the Getting Prepared section. The Flashing section will explain how to actually start the flashing process. It's important that you don't skip ahead! Ensure you've prepared everything correctly!

Getting prepared:

Remove all external power from the unit, and prepare SP-Flashtool with your scatter file and backup files. Do not connect the USB cable yet. If you are using system.img, userdata.img, recovery.img etc, make sure all the paths to the files are correct on the Download tab. As long as you have not attempted to modify the partition file, you can flash in Download Only mode, and you're good to go. If you have attempted to modify the partition table, the most reliable way to ensure that your backup loads correctly is to flash only your preloader first on the first pass, and then do another pass in Format All + Download mode with all of your files selected. After your preloader is restored, you should not need to use the test point for the second pass.

If your backup is a ROM dump, and you have a BOOT_1, BOOT_2, and EMMC_USER backup file, then you will need to use the "advanced mode" in SP-Flashtool to restore. While in SP-Flashtool, press Ctrl + Alt + v to enable advanced mode. Then from the Window menu at the top, check the box for Write Memory, and switch to the newly opened Write Memory tab. For the file path entry, browse or type the path to your BOOT_1 backup. Set the Begin Address to 0x0. After flashing BOOT_1, you will need to repeat the flashing process for BOOT_2 and EMMC_USER, but once BOOT_1 is flashed, your preloader is restored and you should not need to use the test point to restore the other files.

Flashing:

At this point, you should have SP-Flashtool prepared with your backup files and the unit should be disconnected from power and USB. In the next step you'll need to have the test point shorted as you plug the USB in, and remove the short when the tool connects to the factory preloader so get prepared to do that. If you're in the Download tab at this point, click the Download button, if you're in Write Memory mode, click the Write Memory button. SP-Flashtool will start looking for a device. Plug in your USB cable with the test point shorted on your board. Once SP-Flashtool recognizes the device, you usually need to give it a couple of seconds to initialize the connection before you remove the short. You may have to try a few times to get the timing right. If you remove the short too quickly or hold it in place for too long, the connection will fail and you'll need to try again. Once you get it right, it should begin flashing as normal. If you're only flashing your preloader on the first pass, you should not need to use the testpoint to get SP-Flashtool to recognize your device on subsequent passes. Finish reloading all of your backup files and you're done! You should have a functional device!