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G981U and G981U1 Firmware Links and Flashing Discussion Here

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sreyn

Member
Aug 15, 2021
6
0
Newbie that probably made a mistake......

I purchased an unlocked, G981U1 phone. Worked okay with AT&T but I didn't have some features including WiFi calling. The phone had TMB software per review of the Software Information screen. Decided to change to AT&T's U firmware to try to get WiFi calling. I first tried the firmware in the link in the OP of this thread (G981U_TAW_1). First step seemed to update okay (BL, AP, CP, no home CSC) but I never got the "reboot to apply new carrier settings" and the software still seemed to be from TMobile since I saw still saw TMB in multiple places on the software information screen page. I then gave G981U_UDA_2 firmware a try. This updated fine but then I had the T-Mobile splash screen and I could no longer get service with my AT&T sim. I tried uploading the USERDATA file but that didn't make any difference. I am now reading more about this UDA and think that I now have a bootloader that won't let me go back to a U1 version. I am using Odin 3.14.4 but get the SHA256 error. At this point I would like to get either to the AT&T U version or the generic U1 software. I hope it's not too late to yell HELP!
 

mcssym

Member
Aug 11, 2018
7
0
After reading this thread, it seems it's better a U than a U1.
I just bought a SM-G981U1/ATT unlocked. I wonder why I have ATT instead of XAA.
So, my question is:
Should I pass the firmware U1/ATT to U/XAA?

Thank you
 

mcssym

Member
Aug 11, 2018
7
0
It shows ATT because that's where it's originally from. Then someone flashed U1 firmware to it
Ok, I bought it refurbished from Amazon.
But so, you confirm is better the firmware U/XAA?

Anyway, I don't have the option "Unlock OEM", I deduce that the bootloader is locked as all the U/U1. But if you say someone flashed U1 on it, my bootloader is supposed to be unlocked so?
 

iBowToAndroid

Senior Member
Nov 9, 2010
4,700
1
1,460
Twin Cities MN
Ok, I bought it refurbished from Amazon.
But so, you confirm is better the firmware U/XAA?

Anyway, I don't have the option "Unlock OEM", I deduce that the bootloader is locked as all the U/U1. But if you say someone flashed U1 on it, my bootloader is supposed to be unlocked so?
No, your bootloader is not supposed to be unlocked. Whoever told you that doesn't know anything about bootloader unlocking
 

mcssym

Member
Aug 11, 2018
7
0
First of all, XAA belongs to U1 firmware, not U firmware

Second, what's the current phone's Baseband Version? (And don't do any software updates, if it asks you for one)
1. Ah ok, so if I use a U firmware, what is the CSC?

2. G981U1UES2DUH2, and sorry, but trying a method to get OEM Unlock at the beginning, I did all the updates till September 1st. Can't I downgrade?
 

iBowToAndroid

Senior Member
Nov 9, 2010
4,700
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1,460
Twin Cities MN
1. Ah ok, so if I use a U firmware, what is the CSC?

2. G981U1UES2DUH2, and sorry, but trying a method to get OEM Unlock at the beginning, I did all the updates till September 1st. Can't I downgrade?
1. U firmware is universal. It doesn't matter which CSC you use, since they're all the same

2. No, you can't downgrade. If you had an older version, then the bootloader would be unlockable via paid services. But since you updated, never mind.
 

mcssym

Member
Aug 11, 2018
7
0
1. U firmware is universal. It doesn't matter which CSC you use, since they're all the same

2. No, you can't downgrade. If you had an older version, then the bootloader would be unlockable via paid services. But since you updated, never mind.
So, even with paid services, I can't unlock the bootloader?
If I don't update more, do you think in few weeks this will be possible?
Putting the U firmware can resolve it but I need the bootloader for that, right?
 

iBowToAndroid

Senior Member
Nov 9, 2010
4,700
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1,460
Twin Cities MN
So, even with paid services, I can't unlock the bootloader?
If I don't update more, do you think in few weeks this will be possible?
Putting the U firmware can resolve it but I need the bootloader for that, right?
1. No, you can't unlock the bootloader no matter what

2. No, I don't think it will become possible in a few weeks

3. Putting U firmware will resolve what, specifically?
 

big_sea

Senior Member
Jul 20, 2011
66
2
I bought a SM-G981U from T mobile.
Received the phone, unlocked it within android.
Flashed the SM-G981U1 VZW firmware from Frija/Odin patched 3.14.1
All works well and we have no Verizon apps.
Unfortunately, no voice mail app and others.
Any way to flash the SM-G981V user data to the phone from Odin? Or will that cause issues?
 

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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
    1
    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
    1
    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
    1
    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
    1
    Got it figured I used the wrong firmware
    Oh okay :)