[Desire 820 Android Development] Gibz97:
I'm quite new to mediatek devices but from my experience with this device so far, the entire firmware is distributed into partitions that are dictated by the scatter file.

When you open the scatter file with a text editor like notepad ++, it clearly shows the different partitions within the firmware.

Other than file names, it also shows the start addresses (physical and linear) of every partiton which is the point at which the partition begins. It is shown in hex values, with a programmer calculator you can convert them into decimal values and know exactly the point of start of a partition in terms of Bytes(you can convert to KBs,MB or GB). I don't know the difference between physical and linear addressees so far but they have the same exact value for each partiton.

Then there is the partition size. As the name suggests this is the size of the partiton, same thing, hex values. Now if you want to try and flash a file that exceeds the limit of a partition's size SP Flash Tool will throw an error about overlap since it is too big to fit.

Same thing with the bootloader. It occupies the lk partition, but the lollipop one is larger than the kitkat partition so if you wanted to flash it on kitkat, you'll have to increase the size of the lk partition by editing the scatter file(DANGEROUS). So if you increase the size of a partition you will have to edit the entire scatter file after that partition because you will have altered the start address of the next partition and the next... till the end. I wouldn't advise anyone to do that.

Coming to the decrypted lollipop firmware, it is about 99% complete, but It misses some important partitions like : persist, pg1fs and pg2fs which I believe are responsible for securing the bootloader, making it impossible to boot without them because the bootloader thinks security has been breached.

The other important absent partition is carrier for your carrier,no wonder the bootloader showed superCID. Others are Battery and lkbackup.

Lollipop scatter file

Kitkat scatter file

---------- Post added at 07:10 PM ---------- Previous post was at 07:09 PM ----------

With an SP Flash Tool readback you are able to backup the entire partition:

It doesn't require root and does not flash anything on your phone.

On our devices it can be performed by:

1. Go to download section and load exact scatter file for your firmware at download section. (If you have Lollipop on your phone then load the lollipop scatter file)

2. Uncheck every item

3. Go to readback section, let the type be 'hex'

4. Click add

5. Double click on the added item and choose the name of the file you want to backup as per the scatter file. Should be the File_name of the partition in the scatter file. if it is NONE then save it as partition_name and add ".img"

6. Set the start address to linear start address of the partition in the scatter file.(or physical start address, they are the same).

7. Set length to partition size as per scatter file for that partition

8. You might add another partition if you want to backup more than one partition, (same procedure)

8. Click Ok

9. Click on Readback

10. Switch off phone and connect it to PC via USB cable, DO NOT interrupt until it finishes and hey you've backed up an entire partition in your phone.

You can repeat this for every partition and backup your entire firmware.

If I'm wrong someone can correct me.