[Upgrading, Modifying and Unlocking] A23511:
Recently I received a request from a friend to help them with a tablet. The complaint was lots of adverts showing when using the tablet. Some info:

Manufacturer: Denver

Make: TAQ-10123 MK2

Model: PO-9839

Android: 5.1.1

Code Name: astar_m100 (astar-m100)

PCB is labelled 'Eferco M100_MB 3.0'. CPU-Z identifies it as follows: 'Cortex' + 'Allwinner A23 1.34GHz' + '4x ARM Cortex-A7 @ 1.34GHz', Model 'PO-9839 (astar_m100)', Manufacturer 'Denver', Board 'exdroid', Hardware 'sun8i', Screen Resolution '1024 x 600', Build ID 'astar_m100-eng 5.1.1 LMY47V 20160304 test-keys', Android Version '5.1.1', API Level '22'.

Manufacturer product webpage: denver-electronics.com/denver-taq-10123mk2/

(archive link): web.archive.org/web/20170317121038/denver-electronics.com/denver-taq-10123mk2/

I asked the manufacturer for the factory firmware and they sent me a 'wetransfer' link. I have re-compressed their ZIP archive into a 7Z archive, saving several hundred MB and re-hosted it on Mega.

Factory firmware: mega.nz/#!s4MAFTLa!TqrXXHShfxvqNg6wwQ10LsS2VuZQWgNGfmklouVLr-8

Just a warning, the default file manager installed on the tablet and also in the factory image is infected with a trojan. Specifically, /system/app/FileExplore/FileExplore.apk is detected as infected with 'Backdoor.AndroidOS.Coudw.a' by both Malwarebytes & Kaspersky. Virustotal scan results here: virustotal.com/en/file/e99b9b1d976cce2d4b34afc918950a6a71295e4694ec60a86c0494daf0f89872/analysis/1488895182/

Likely the source of all the adverts and crap. The tablet comes with an insecure ADB configuration by default, so once you install the necessary drivers and connect it to your computer, you can use ADB to have root access to the device. This makes it easy to disable or remove the infected file manager.

The device has an unlocked bootloader and you can easily flash your own firmware images.

The device is built using an Allwinner A33 SoC. CPU-Z will falsely identify this as the A23, but as the device is Quad-Core, you can clearly tell it is based on the A33 SoC. Further information can be found here: linux-sunxi.org/A23 & linux-sunxi.org/A33.

Information on partition layout here: linux-sunxi.org/Android/partitions

I have managed to hack together a working TWRP build for this device. As most A33 devices out there seem to be running 4.4, this may be of use to other tablet owners running Allwinner A33 based tablets that are running 5.1.1. I have compressed and uploaded to Mega.

TWRP: mega.nz/#!NkUCBJLQ!IL2Htl_0DifU-_wjuRD6ESwiCGw2-CxlumYmn9K9e7w

To flash, start the tablet normally and then connect to a computer, run 'adb reboot-bootloader'. Once that is complete, install the proper drivers if they don't auto-detect, and then run this command 'fastboot -i 0x1f3a flash recovery TWRP.img' - modifying the name of the IMG to whatever you have named it. Also, this device is a bit weird in that to boot to recovery, you have to hold down VOL+ and POWER and then quickly release VOL+ and then press and hold it again, releasing POWER shortly after the 'DENVER' logo shows on the screen. (otherwise it won't power up).

I used many different sources of information in getting this far, I will try and link them in later. For now - at least you have a TWRP image so you can easily root and begin hacking away. Also the default firmware means you can easily recover from any mistakes.

How to back up the firmware already on your device: xdaforums.com/showpost.php?p=55973453&postcount=12

This gives you something to safely restore from in case you can't get a factory firmware image for your unit. For additional advice, see this thread: xdaforums.com/showthread.php?t=2450045

Other Allwinner threads:

xdaforums.com/showthread.php?t=3038123