[General Topics] CatStoleTheCrown:
Xiaomi Qin F21 Pro with US Bands

LTE Bands 2, 4, 12, 13, 17, 66, 71 as provided by the US Qin F30 Kosher.

Things you need:

Windows PC (as far as I know this only works on Windows)

Qin F21 Pro with unlocked bootloader and TWRP installed.

See: https://xdaforums.com/t/tools-mod-scripts-mlgmxyysds-qin-f21-pro-unlock-tool.4368277/

(This can be a headache, there are probably better ways to do this.)

See: https://xdaforums.com/t/guide-xiaomi-qin-f21-pro-custom-firmware-root-playstore-certified.4405615/

You only have to follow this tutorial up to the point of installing the boot_2.img in TWRP you do not have to root if you don't want to. I do believe most of us with F21's probably have already done this entire tutorial though.

SP Flash Tool: See tutorial above, it comes with it.

ADB (and please know how to use it): https://www.xda-developers.com/install-adb-windows-macos-linux/

The files I provide with this link :)Which are: F30 files (from my purchased F30), my edited scatter file to show new partitions, SN Write tool with provided Database files.

https://www.mediafire.com/file/3fba0dugos3lkdv/F30_US_LTE_Bands_Package.zip/file

I WILL NOT BE HELD RESPONSIBLE IF YOUR PHONE DOESN'T BOOT, SOFT/HARD BRICKED! THIS TUTORIAL IS TO DO AT YOUR OWN RISK!

GUIDE:

1. Write down your F21's Original IMEI, Wifi Mac Address, and Bluetooth Address.

Go into your phone settings and scroll all the way down to "About Phone".

Here you will find your IMEI, Device Wi-Fi MAC address, and Bluetooth address.

WRITE THESE DOWN!!!!!!!! YOU NEED THESE LATER!!!!!!! I even included a txt file for you to do it in!

We want to write these down because we will need them for the SNwriter tool later.

2. Turn off your phone and boot into TWRP, you can do this by holding the heart/owl key (top left) and the * (star, bottom left) key, you will see the Douqin Logo. Keep holding until TWRP boots.

3. Plug the F21 into computer and TWRP will allow ADB connections. We are going to use ADB to pull/backup your modem and identifier files in case you mess up =)

DO NOT SKIP THIS STEP. WE WILL BE OVERWRITING THESE FILES - THEY CONTAIN THE IDENTIFIERS THAT YOU WROTE DOWN ABOVE.

Even though we will no longer be using these files, they are original to your phone, and I think its incredibly important to have a back up. I even included an empty folder for you to put them in!

Use the following ADB commands:

adb pull /dev/block/by-name/nvdata

adb pull /dev/block/by-name/nvram

adb pull /dev/block/by-name/nvcfg

Now find those files and put them some where safe!!!

(You can also use TWRP and copy the files, and put the on a USB stick or maybe some where else on the phone)

4. Turn off the phone again, you can do this from TWRP by going to Reboot and chosing Power Off.

5. Open SPFlash Tool and load the scatter file provided from my files "MT6761_Android_scatter - edited.txt". This will add the NVData, NVRam, NVcfg partitions to flashable partitions.

5a. Uncheck all the boxes we don't need and only check off nvcfg, nvdata, nvram, and md1img_a. These are the ONLY partitions we are flashing. (They should already be selected! BUT SO WILL THE PRELOADER, UNCHECK PRELOADER, I had to include it in the folder for the flashing to work, but we do NOT need to flash it!)

5b. Click the "location" portion of each row and find the corresponding file from the files I provided. (This should already be done!)

5c. When you got everything set up, click the Green Arrow Download button. With your phone turned off, hold the BACK button (top right) and plug it in. It will flash these files to your phone. KEEP YOUR PHONE OFF FOR NOW.

6. Open SNwrite tool on your computer, make sure ComPort says USBVCOM, and Target Type says Smart Phone.

6a. Open the System Config button and make sure ONLY IMEI, BT Address, and Wifi Address are checked off in the "Write Option" (top left) section.

6b. In the DataBase File section (at the bottom) and make sure "Load AP DB from DUT and Load Modem DB from DUT are checked.

6c. Click on the MD1_DB button and select the "MDDB_InfoCustomAppSrcP_MT6761_S00_MOLY_LR12A_R3_MP_V88_3_1_ulwctg_n.EDB" file located in the AP DB Base\\MT6761 folder (within SNwrite folder).

6d. Click on the AP_DB button and seelect the "APDB_MT6761_S01__W1947" file located in the AP DB Base\MT6761 folder (within SNwrite folder).

6e. Click Save and go back to the main window, click on "Start" and a new window will pop up. Remember how I told you to WRITE DOWN all of these from your F21? This is where we need it.

IMEI_1 = your original IMEI.

BT Addr = Your Bluetooth Address (no colons!)

Wifi Addr = Your Wifi MAC Address (no colons!)

6f. Before you click OK be sure to have your phone at the ready. You will need to, just like with SP Flash Tool, hold the back button as you plug it in! Click OK and plug in your phone with the back button held. Wait for the bar to progress and the green PASS signal to light up.

6g. When its done, your original identifiers will be flashed to your phone! Another window may pop up making you think you have to flash again, just close it as long as you saw that Green PASS signal you are good.

7. TURN ON YOUR PHONE AND ENJOY US LTE BANDS!!!!!! 2, 4, 12, 13, 17, 66, 71

These cover most of T-mobile and Verizon users!

Go back into your phone settings as in Step 1 and make sure your original IMEI, Wifi Mac Address and Bluetooth Address are there.

To confirm the bands, use the phone dialer and type:

*#*#3646633#*#*

This will take you into engineering mode (use at your own risk, don't mess with anything!) and click on Band Mode. Scroll thru the bands and you can confirm which ones are active. As far as which ones are currently being used, I am unsure of how to do that just yet. Will update when I know (was told there are apps that might be able to do this).

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Things to note:

AGAIN: BE SURE TO BACK UP YOUR FILES and write down your IMEI, Wifi MAC ADDRESS and BLUETOOTH ADDRESS! I cannot state this enough.

If you do not do the SNwrite tool (section 6 of the steps) you will have DUMMY made-up identifiers, and technically those will work for a while.. but you don't want to have the same ones as others, so please do section 6.

I cannot help you with unlocking your bootloader, that part can be easier and the tool I linked was not fun. There are apparently much easier ways, please look into them.

If you can unlock your bootloader, and install TWRP you can do the rest of these steps easy!

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If you would like to buy me a coffee: https://ko-fi.com/storymode

I'd like to thank:

Jbazt_katuforzs (XDA forums) for the Unofficial Qin F21 Pro firmware tutorial.

Sense_101 (XDA forums) who I couldn't have done this without, they helped me with learning ADB commands and knowing which files I would need to get this done.

mosheys (XDA) who told me about SNwrite tool.. which I knew about, but couldn't work before, and gave me the motivation to try again, really made this all come together.

jbriones95 (Reddit) who got me into Dumbphones and introduced me, through his videos, to the F21 Pro. The perfect phone for me!

eitokai (Reddit) who worked on tinkering with the F30 and made me believe I could do it too, and make progress - and everyone they thanked helped too!

Quick shout outs to Highpowers23 (Reddit), and 154FAviator (Reddit).

Lots of other random tutorials online where other people were trying to do similar things with their phones!!

-edits-

4/25/23: Fixed an issue where SPFlash tool was giving an Invalid Preloader error on Step 5a. I had to add the preloader file to the supplied download, but we do NOT need to flash the preloader. Edited step 5a to reflect change. Thanks to XDA user mosheys for pointing it out =)