Resources for Samsung Galaxy TAB A 7.0 (2016) SM-T285

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gian20

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Apr 19, 2013
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I have a problem in my SM-T285 the Device is encry pted with a password. After the device locks, the keyboard is gone from the lock screen so you can't type the password. I don't know if this is a bug but I am using the default samsung keyboard and hacker's keyboard (fdroid). Anyone encountered this issue? I don't know if this persist only in encrypted devices... I've tried resetting the device to factory defaults and encrypting again so it maybe a bug? I am using the stock firmware that was released on Mar 2016. (initial firmware)

I have rooted and installed TWRP. and changed the boot password from the screenlock password.
Upon entering the boot password the android boots and displays the lock screen. the keyboard popups for about 30 seconds and disappears forever* since you cannot unlock the tablet because there is no keyboard popping up. (might be a BUg in android?)
Is there a way to force change the screenlock password to a pattern lock? It is greyed out because I have used the device encryption...
 
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gian20

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Apr 19, 2013
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I 've tried to Wipe Data and Factory Reset, the SELinux from ABout device is still not visible. I don't know but the SUperSU is gone after Factory reset of /data. So it may the TWRP installation using heimdall? I haven't tried to Flash a stock firmware since the device is under wranty.

Any idea on how to force set pattern lock on the screen lock it is currently a 'Swipe' unlock which is not secure, but boot paswsowrd is still requiered...
 

jedld

Senior Member
Oct 15, 2007
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I don't know but the SUperSU is gone after Factory reset of /data. So it may the TWRP installation using heimdall?

Not entirely true, SuperSU makes permanent changes to the boot and system partition that survives a factory reset. The only way to remove SuperSU/root is to flash stock boot and system images.
 

gian20

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Apr 19, 2013
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?

Not entirely true, SuperSU makes permanent changes to the boot and system partition that survives a factory reset. The only way to remove SuperSU/root is to flash stock boot and system images.
When I tried to factory reset, (reformat /data) the supersu is gone so I need to flash the SR5-SUpers-* again to get the SU (Root Mode). Before flashing the SELinux from the about device is gone, maybe because of the earlier flash of TWRP or SR5-SuperSU., by the way in the download mode, that is the "MDM DOWNLOAD BLOCK: 0". and currently i am trying to debloat my tab using the stock firmware what apps/system can be safely removed? thanks
 

serv-inc

New member
Jan 7, 2017
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FRP lock after missing OEM unlock

Hi all,

after installing a custom ROM with root (thanks, ashyx and jedld), the device worked fine - until the reboot. I had missed the "OEM unlock" part. The device is a 280 Now the only modes that work are Download and Recovery (the latter after Samsung returned the device). All other modes show the Custom binary blocked by FRP lock-message. I tried downloading a stock rom from sammobile, but flashing it did not fix the problem (maybe I chose the wrong ROM, there are quite a few to choose from).

Any help? Thanks in advance

serv-inc
 
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ashyx

Inactive Recognized Contributor
Oct 14, 2012
15,087
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Hi all,

after installing a custom ROM with root (thanks, ashyx and jedld), the device worked fine - until the reboot. I had missed the "OEM unlock" part. The device is a 280 Now the only modes that work are Download and Recovery (the latter after Samsung returned the device). All other modes show the Custom binary blocked by FRP lock-message. I tried downloading a stock rom from sammobile, but flashing it did not fix the problem (maybe I chose the wrong ROM, there are quite a few to choose from).

Any help? Thanks in advance

serv-inc
Installing the correct firmware for your device region will remove the frp lock.
Do NOT factory reset your device while the lock is in effect.
 
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serv-inc

New member
Jan 7, 2017
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Installing the correct firmware for your device region will remove the frp lock.
Do NOT factory reset your device while the lock is in effect.

Thanks. So how to determine the correct firmware? Should I just try all 4 that exist for my country? And should I flash all images (including sp2.img etc)?
 

ashyx

Inactive Recognized Contributor
Oct 14, 2012
15,087
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Thanks. So how to determine the correct firmware? Should I just try all 4 that exist for my country? And should I flash all images (including sp2.img etc)?
Not sure you're flashing the right thing there.
The firmware package will be in md5 format and will be flashed as a complete package with odin.
Find the one for your country and just flash the latest.
 
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serv-inc

New member
Jan 7, 2017
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Not sure you're flashing the right thing there.
The firmware package will be in md5 format and will be flashed as a complete package with odin.
Find the one for your country and just flash the latest.

Thanks. I used heimdall, where I selected the .bin files to flash. Let me see if it can somehow used differently...
 

macapa1994

Member
Sep 12, 2012
20
8
what do you thing about any hope for ROM like lineageOS, cyanogenmod, candy, AOSP or whatever for the model T280? I hate ROM stock and the touchwiz :'(
 
Maybe, one day?

what do you thing about any hope for ROM like lineageOS, cyanogenmod, candy, AOSP or whatever for the model T280? I hate ROM stock and the touchwiz :'(

The problem with the SM-T280 is that we don't yet have a working selinux permissive kernel. I imagine once that happens (if ever), we'll see other ROMs. For now, I'm more than happy to run jedld's custom Tinker Edition on my SM-T280.
 

jedld

Senior Member
Oct 15, 2007
430
438
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The problem with the SM-T280 is that we don't yet have a working selinux permissive kernel. I imagine once that happens (if ever), we'll see other ROMs. For now, I'm more than happy to run jedld's custom Tinker Edition on my SM-T280.

If anyone is willing to part with their T280 or donate one to me, I'll be willing to work on it. It is quite unfortunate that the T280 isn't offered in my country otherwise I would have taken care of this device by now.
 

One.Hit.Kill

Member
Jun 17, 2014
19
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Lake Worth
If anyone is willing to part with their T280 or donate one to me, I'll be willing to work on it. It is quite unfortunate that the T280 isn't offered in my country otherwise I would have taken care of this device by now.

If anyone starts a donation page to get jedld to get an SM-T280 let us know. I'll definitely donate at very least $50. The SM-T280 is around $130 in the USA at most retailers. I can't imagine shipping being more then $50 reguardless which country it is going to. So this should be somewhat easy to achieve.
Thank you
 

gian20

Senior Member
Apr 19, 2013
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Member52 posts Thanks: 2

hi, i am stuck at bootloop. I am using the stock firmware *APCN then I have encrypted my device. Decryptd and factory reset using TWRP 3.0.2.0. now I have download the xtreme version "CM13-XTRM-20170116-2-UNOFFICIAL-SMT285-BETA.zip". I am using GNU/Linux and tried to flash using Heimdall.
Commands executed:
$ tar -xvf CM13-XTRM-20170116-2-UNOFFICIAL-SMT285-BETA.zip
# Vol + Home + Pwr = DOwnload Mode
$ sudo heimdall flash --RECOVERY ./recovery.img
$ sudo heimdall flash --KERNEL ./boot.img
$ sudo heimdall flash --SYSTEM ./system.img

then the device is not boot looped showing the Marshmallow logo (animation). I don't know what triggered it. does the boot.img from the ZIP and tar.md5 corresponds to the partition KERNEL or BOOT ? Please help
 

jedld

Senior Member
Oct 15, 2007
430
438
Bacoor
Member52 posts Thanks: 2

hi, i am stuck at bootloop. I am using the stock firmware *APCN then I have encrypted my device. Decryptd and factory reset using TWRP 3.0.2.0. now I have download the xtreme version "CM13-XTRM-20170116-2-UNOFFICIAL-SMT285-BETA.zip". I am using GNU/Linux and tried to flash using Heimdall.
Commands executed:
$ tar -xvf CM13-XTRM-20170116-2-UNOFFICIAL-SMT285-BETA.zip
# Vol + Home + Pwr = DOwnload Mode
$ sudo heimdall flash --RECOVERY ./recovery.img
$ sudo heimdall flash --KERNEL ./boot.img
$ sudo heimdall flash --SYSTEM ./system.img

then the device is not boot looped showing the Marshmallow logo (animation). I don't know what triggered it. does the boot.img from the ZIP and tar.md5 corresponds to the partition KERNEL or BOOT ? Please help

Your heimdall commands look correct. My only advice is that you reformat your /data /cache partition using ext4 or f2fs. Also be patient, the first startup takes a while.
 

gian20

Senior Member
Apr 19, 2013
91
7
Manila
Your heimdall commands look correct. My only advice is that you reformat your /data /cache partition using ext4 or f2fs. Also be patient, the first startup takes a while.

the first bootloop was : reboot after 10 seconds of marshmallow animation
(I tried to Wipe data partition using the TWRP 3.0.2.1 asphyx)
second: endless boot animation (still waiting for the boot to complete almost 20 minutes now...)
 

jedld

Senior Member
Oct 15, 2007
430
438
Bacoor
the first bootloop was : reboot after 10 seconds of marshmallow animation
(I tried to Wipe data partition using the TWRP 3.0.2.1 asphyx)
second: endless boot animation (still waiting for the boot to complete almost 20 minutes now...)

Try using advance wipe and try to switch filesystem from ext4 to f2fs vice versa. Do try to reflash boot and system again if it persists.
 

gian20

Senior Member
Apr 19, 2013
91
7
Manila
I am gonna try that build, but it will take me 7 hours to download it so I'll update after flashing it. thanks
 

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  • 13
    I've just got a new Samsung Galaxy TAB A 7.0 LTE SM-T285, For some reason I can't seem to find any resources for this hardware yet in this forum, anyone know where I could find one? I'll try to find out if the current methods (custom recovery and root) for other tab versions work on this.

    CUSTOM ROMS
    ============

    Android 5.1.1 Lollipop (Stock)


    Tinker V5 Edition based on the Samsung Stock Rom SM-T280/T285


    Android 6.0 Marshmallow

    Cyanogenmod 13 for the SM-T285 Only
    OMNIRom for the SM-T285 Only

    Android 7.1 Nougat

    Cyanogenmod 14.1 for the SM-T285 Only (Experimental, things are broken, depcrated in favor of LOS 14.1)
    LineageOS 14.1 for the SM-T285 Only

    Other Operating systems

    Porting for Sailfish OS is currently in progress for the SM-T285, stay tuned

    TWRP RECOVERY AND ROOT
    =======================

    TWRP is available for both the T280 and T285. You should find the relevant threads in this Galaxy Tab A forum.

    If you want to root stock, easiest way is to install TWRP and go for SuperSU. Please see the TWRP threads for SM-T280/T285 on how to root after TWRP is installed.

    KERNEL
    ======

    Custom kernel with working sources for the SM-T285 can be found Here

    DEVELOPMENT
    ============

    If you want to build LineageOS 14.1 on your SM-T285 LTE device, you can use this manifest, not that this is still a work in progress:

    https://github.com/jedld/android.git

    UPDATE 10/06/2016
    ================

    After a couple of weeks of trial and error and tinkering, I've been able to compile a kernel for the SM-T285 from source and so far it seems to work flawlessly!

    Screenshot here: http://imgur.com/a/HRgsq

    link to my kernel sources here: https://github.com/jedld/kernel_samsung_gtexslte.git

    You can also thank samsung for giving us a "broken by default" kernel source. I had to mix and match defconfigs from their other kernel releases just to make this thing work. Download modified boot.img here:

    http://forum.xda-developers.com/galaxy-tab-a/development/kernel-galaxy-tab-7-0-2016-lte-sm-t285-t3474967

    UPDATE 09/20/2016
    ================

    This device is now ROOTED!

    http://forum.xda-developers.com/galaxy-tab-a/help/resources-samsung-galaxy-tab-7-0-2016-t3431022/post68777842#post68777842

    Download Pre-rooted Tinker Edition V5 in this thread: Tinker Edition Thread

    Post Root Post Mortem Analysis for the SM-T285 (09/21/2016)
    =========================
    Q: How were you able to find root? What did you do?
    A: Surprisingly the SM-T285 bootloader isn't actually locked like we thought it was (Once you OEM unlock of course and disable FRP). The bottomline is that
    we simply needed patches to mkbootimg to properly package a boot image for this device as there were additional fields and sections not found on a normal boot image. There were even minor breaking difference between the tab 4 and the boot image for this device.

    Q: I thought the bootloader was locked?? Why did it take so long?
    A: I blame it on the really vague errors the bootloader shows when loading an improperly packaged boot image. What helped was my faith to open up a hex editor when I needed to, and really look at the stock images and the images we were making. What really pushed me to investigate further was the fact that I was able to make a really small modification to the ramdisk and use the abootimg -u update function instead of the create options.

    Q: So the bootloader doesn't really check the image?
    A: Yup, The bootloader doesn't do any check. I haven't checked if that is the case for the recovery partition though. Even without the SELINUXENFORCE headers at the end it still continues like other samsung devices do.

    Q: So the mkbootimg patches are all that we need?
    A: Yup, if you have CM, AOSP build env ready you can simply add the modified mkbootimg to system/core:

    https://github.com/jedld/degas-mkbootimg/commit/b63ae38e2ab7040cc7ddaef777652a56b2e48322

    Sample usage below:

    Code:
    degas-mkbootimg -o boot.img --base 0 --pagesize 2048 \
      --kernel boot.img-zImage --cmdline "console=ttyS1,115200n8" --ramdisk boot_kitchen/boot.img-ramdisk-new.gz --dt boot.img-dt

    Next challenge will be getting Cyanogenmod on this device as well as TWRP.
    5
    rooted. The Galaxy Tab A 7" 2016 LTE (SM-T285) now joins the family of rooted devices. Now uploading the latest pre-rooted ROM. Will work on the SM-T280 next.

    uploaded the boot.img now. Sorry I have a slow net connection.

    Proof below for the unbelievers:

    http://imgur.com/a/7Bl8t
    4
    @ashyx - Reversed engineered the 280 header and came up with the following notes:

    The header is 512 bytes long.
    First 8 bytes consists of magic - 0x44 0x48 0x54 0x42 0x01 0x00 0x00 0x00 - DHTB
    This is followed by a sha256sum of the payload. Note that the "payload" starts with the start of the ANDROID header until the first 20 bytes of the SEANDROIDENFORCE header
    Followed by 4 bytes which I think is unused and then followed by a 32-bit unsigned integer consisting of the size of the payload.
    After that it is mostly empty bytes as far as i can tell.

    This is true for both boot and recovery headers.

    Below is the sample header of the DHTB header of the T280:

    < 00000000: 4448 5442 0100 0000 4b40 f348 e206 7672 [email protected]
    < 00000010: 8fe4 72c2 06ed 0fdd 9df7 16d7 80d0 fc64 ..r............d
    < 00000020: 17bd 6594 5881 07b2 0000 0000 0000 0000 ..e.X...........
    < 00000030: 1498 d600 0000 0000 0000 0000 0000 0000 ................


    We can see that payload is 14063636 long, original boot.img is 14064808 long, the seandroid header is 680 bytes long so we do the math
    14064808 - 512 (Size of the DHTB header) - 680 (seandroid header) - 20 (we include the SEANDROIDENFORCE magic string)
    =
    14063636 = 0x00d69814 , then swivel to account for endianess 0x1498d600

    afterwhich I computed the sha256sum of the 14063636 byte payload and got 4b40f348e20676728fe472c206ed0fdd9df716d780d0fc6417bd6594588107b2
    which matched the checksum value.

    Hope with this information, T280 users can get what they deserve so much :)

    Thanks, that was great info.
    I'd noticed the header magic was the same in the boot images and recovery after doing binary comparisons.

    I'd assumed that somewhere in the header would be the checksum and I'd already created a checksum from the payload and then tried to search for it in the header and footer, but came up with nothing. However I didn't include the SEANDROIDENFORCE magic string, which makes sense now as the rest is the signature. When you pointed that out I did it again and sure enough a match in both the header and footer.
    Good catch too with the bytes containing the payload size didn't notice that. Again found this in both header and footer.
    Looks like these are required mainly for ODIN to flash. If not there the bootloader rejects the flash which is why it was hanging on RQT CLOSE!

    I calculated the checksum and converted the payload size to HEX and patched the header and footer.

    Tested this out by modifying the stock recovery which wouldn't flash beforehand with the same mods. Bingo it flashed and didn't hang on RQT close! Still get the 'secure check fail' warning, but I guess that has something to do with the signature.

    Next I moved on to the custom kernel. I recompiled with some slight mods and did the procedure again with the stock recovery, replacing the stock kernel with the custom kernel.
    Flashed...and boom...successful flash again and booted.

    Next up was TWRP for the same treatment, did the whole procedure again and used my custom kernel. Flashed with ODIN and didn't hang this time. Booted to recovery and the result was...




    SUCCESS!
    TWRP now available for the T280.

    Still needs tweaking as the graphics aren't the right colour seems to be using the wrong pixel format and the FSTAB may need adjusting as the EFS is showing 0mb. All easily fixable.

    .
    3
    Alright, I got it all worked out; should be pretty robust now:
    https://github.com/osm0sis/dhtbsign

    :highfive::D

    I'll have support added for Android Image Kitchen v2.9. :cowboy::good:
    2
    Have added the flag for inverting the display. Compiled it with kernel built from latest sources. Kernel was a bit bigger which was slightly worrying.
    Display colours should also be correct.
    TWRP_3.0.2-1_SM-T285_23916

    .

    Thanks! Flashed it and twrp now works properly for me. The kernel I built was a bit bigger too. I'll try to go back to stock and try to re-root my ROM from there. Thanks again!