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G981U and G981U1 Firmware Links and Flashing Discussion Here

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By iBowToAndroid, Senior Member on 22nd February 2020, 12:02 AM
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For those who aren't already aware, G981U is the model number of all of the US carrier versions of the S20. The G981U1 is the model number of the same device, but sold by Samsung SIM unlocked and with no carrier bloatware. Firmware is 100% interchangeable among these models: any U or U1 firmware version can be flashed to any U or U1 device at any time, assuming that you're not trying to downgrade the bootloader. A "U to U" or "U1 to U1" flash does not require a factory reset, but changing from one firmware to the other will require one. Also, U firmware is identical for the 4 base files (AP, BL, CP, CSC) for each individual build, no matter which carrier it comes from. So if you download 2 different carrier versions of the exact same build, the 4 base files will be identical. Where the firmware differs is in the USERDATA file - that's where the carrier bloatware and customizations reside.

Manual Odin flashing is designed for those who:

- want to manually update to a newer version of U firmware on their U device, either because they don't want to wait for their carrier's OTA or because OTAs aren't working on their device, or a different carrier got a new feature/patch before they did
- want to flash U1 firmware to their U device
- want to convert from U1 firmware to carrier U firmware
- want to convert from one carrier's U firmware (with all apps and bloatware) to a different carrier's U firmware (with all apps and bloatware)

For those who aren't already aware, anyone can now download firmware for almost any Samsung device any time that they want, via SamFirm or Frija. There are threads and info about them here on XDA so I won't waste time explaining - do a search if you're not already familiar with these tools. But they only provide whatever the latest/newest/current version is - nothing older. I pay for a subscription to a site that gets the official releases (usually) before they hit SamFirm/Frija, so that's where my files come from. However, I don't have unlimited bandwidth on the site, and it's also quite time consuming to download the files, zip them up, and upload them to AFH. And, I do threads like this for every single Sx and Note x model - so I won't be uploading every single version. The only full builds that I upload are ones where I get access to a new bootloader and/or Android version early, before they hit SamFirm/Frija.

This is not a "beginner's guide to Odin flashing" -type post/thread, so I won't list basic, step-by-step flashing instructions. My threads are geared towards those who already know what they're doing. If you're new to manually flashing Samsung firmware (or haven't done it in a long time), I recommend you consult one of those "beginner's" guides- there are tons of them here on XDA.

Happy flashing!

U firmware: https://www.androidfilehost.com/?w=files&flid=305577
U1 firmware: https://www.androidfilehost.com/?w=files&flid=305578

(Quebec tends to be the fastest download mirror, if it gives you that option)

Notes:

- DON'T QUOTE THE OP WHEN YOU REPLY, kthx

- I have lots of threads just like this one for other Samsung flagships, if it interests you. For those who have already made use of my previous threads for a different device and are upgrading to an S20, welcome back

- My zips are compressed extra small for space and bandwidth savings. The default Windows extractor can't handle it, so you'll need a 3rd party tool like 7zip, WinRAR, etc

- My naming method for folders on AFH is: build - bootloader - Android version
So "SAT - 1 - 9.0" means the full build number ends in SAT, it's bootloader version 1, and it's Android 9.0. When bootloader and Android versions increment, the first build to have those changes will have its folder notated appropriately.

- HOME CSC file keeps data intact; using the other CSC will wipe data. Flashing USERDATA will also wipe data.

- Since AT&T doesn't allow their firmware to be publicly available (for any of their devices), I'll try to always upload at least one USERDATA per bootloader increment for AT&T (and Cricket, if they get this model). I'll also upload any full builds if AT&T is the only carrier to get that specific build, because you won't be able to find the files anywhere else.

- For identifying USERDATAS, and to know what region/CSC to use in SamFirm/Frija:

AIO = Cricket (not available via SamFirm/Frija)
ATT = AT&T (not available via SamFirm/Frija)
BST = Boost Mobile
CCT = Xfinity Mobile (Comcast)
CHA = Spectrum Mobile (Charter)
SPR = Sprint
TMB = T-Mobile
TMK = Metro PCS
USC = US Cellular
VZW = Verizon (available via SamFirm/Frija, but Manual Entry is required - Auto will not work)
XAA = U1 firmware

- the correct procedure for switching from one carrier's firmware to another is:
1. Flash full U1 firmware package including non HOME CSC
2. Upon boot, insert a SIM of the carrier whose firmware you want
3. Watch for the popup that says "reboot to apply new carrier settings" etc, and do it
4. After that restart completes, reboot back to Download mode and flash the full U firmware package, with the USERDATA file of the carrier whose firmware you want
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22nd February 2020, 12:04 AM |#2  
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Pre-release notes:

1. I do not have one of these and do not plan to acquire one, so I have no idea if anything can actually be flashed at this moment - I'm just providing the firmware. Like all other models, I'm assuming patched Odin is needed for this, but it wouldn't surprise me if a new version is needed for this specific device. There's only one way to know though, so as soon as someone gets their hands on one and can try this, please let us know.

2. I don't know if using the HOME CSC will actually save data. I don't get access to that file straight from the source - I have to decompile the regular CSC, remove the parts that initiate the factory reset, and then re-compile it. Based on the S10 and Note 10, I've done what I think will avoid a factory reset. But the S20 has some new partitions, so we won't know for sure until someone tests it. So if you're willing to be that guinea pig, you're responsible for taking proper steps to avoid an FRP lock, make sure your data is backed up, etc
12th March 2020, 03:11 AM |#3  
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So I flashed with Odin with my unlocked from Samsung U1 firmware to the T-Mobile U firmware because I wanted the advanced messaging. Only issue in the beginning was not using the patched Odin, but once I did, no problems.

Tools:
Downloaded from this previous thread, post #2, with Modified Odin and Samsung Drivers https://forum.xda-developers.com/s10...r-att-t3908657

Since it's been awhile since I've done flashing or Odin, I followed this basic guide:
https://forum.xda-developers.com/s10...-faqs-t3936704


Of note, only needed the files from the TAW folder only, did not need the T-Mobile specific U firmware as resetting the phone with a T-mobile sim automatically loaded it.

My quick rundown:

1)Extract the G981U_TAW firmware file you just downloaded. You should get 5 files:
AP (System & Recovery)
BL (Bootloader)
CP (Modem / Radio)
CSC_OXM (OXM CSC file, will wipe your phone)
HOME_CSC_OXM (OXM CSC file, will NOT wipe your phone)

2.)In Modified Odin I added each file to it's respective slot EXCEPT for HOME_CSC as I wanted to do a clean factory reset

3) Put the S20 in Download/ Odin mode. 2 different ways as outlined here https://www.youtube.com/watch?v=ZPSWEL6-gWg&t=8s

4) Once the phone was detected in the COM port number in Odin, I clicked the start button and waited til Odin said "PASS". One thing I noticed was the phone didn't reboot all the way automatically, it actually went into recovery mode and I ended up having to do a factory reset through there because at first it would bootloop and take me back into recovery mode, but after doing a factory reset in recovery mode it restarted just fine with the T-mobile firmware along with the t-mobile apps and advanced messaging working as it should be.
12th March 2020, 08:54 AM |#4  
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I want to flash my unlocked samsung s20 so I can use the ATT Volte and wifi calling but will rom eventually get released
12th March 2020, 04:46 PM |#5  
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Quote:
Originally Posted by jameslee2

I want to flash my unlocked samsung s20 so I can use the ATT Volte and wifi calling but will rom eventually get released

If you're saying that you want AT&T apps and bloatware and features, then all the files that you need are already linked in the OP
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17th March 2020, 05:52 AM |#6  
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I'm worried that I already know the answer, but i'm asking it anyways. I'm currently on a SM-G981N (South Korean version), which is a Snapdragon865 phone. I'm wondering if I can change my firmware to the SM-G981U version to get rid of the bloatware on my phone. For what I read for other phone's this wouldn't work. Perhaps I should start looking for an unbloated SM-G981N rom? Thanks!
17th March 2020, 07:02 AM |#7  
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Quote:
Originally Posted by tijsva

I'm worried that I already know the answer, but i'm asking it anyways. I'm currently on a SM-G981N (South Korean version), which is a Snapdragon865 phone. I'm wondering if I can change my firmware to the SM-G981U version to get rid of the bloatware on my phone. For what I read for other phone's this wouldn't work. Perhaps I should start looking for an unbloated SM-G981N rom? Thanks!

I'm assuming the flash would fail. But there's only one way to know for sure
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17th March 2020, 07:22 AM |#8  
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I'll first try an unbloated korean firmware, until I'll find out if crossflashing between different region phones is safe and working...
18th March 2020, 10:44 PM |#9  
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Quote:
Originally Posted by tijsva

I'll first try an unbloated korean firmware, until I'll find out if crossflashing between different region phones is safe and working...

Is the a recovery for sm-g981u?

Sent from my SM-G981U using Tapatalk
18th March 2020, 11:42 PM |#10  
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Quote:
Originally Posted by Bee101

Is the a recovery for sm-g981u?

Sent from my SM-G981U using Tapatalk

I don't understand what you're asking
19th March 2020, 08:09 AM |#11  
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Tried to flash the unbloated (my assumption at least) of the Korean rom: KOO. Followed the correct steps, flashed without problems but bloatware was not removed, also bootlogo of the original carrier doesn't disappear.
@iBowToAndroid, have you tested this method yourself with the S20 series? Flashing from unlocked to carrier firmware should always work I would say, but the other way around, have you got confirmed results for the S20 series?
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