Repurpose a Android tablet

Posted on by Jesper Ramsgaard

I’m sure out of my comfort zone on this post. I picked up an old Huawei cmr-al09 Android tablet. This device, from 2018, runs Android 9 and is no longer supported. I have never used Android, but the thought of it running a Frankenstein Linux is kind of compelling, so I was curious whether this was really e-waste or if it could get a second life.

I quickly found an XDA Developers forum thread where the community has created a custom rom/os for the device, LineageOS. But I have never tried to unlock, root, or install custom firmware on a phone or tablet before. So this was surely an interesting experience.

LineageOS

LineageOS is an open‑source Android distribution that replaces the manufacturer’s firmware. It is built by the community and is often used to break free of OEM bloatware and regain control of your device. In my case, it can extend the life of an outdated Android tablet.

Hardware overview:

The Huawei MediaPad M5 (model CMR‑AL09) was released in early 2018, which makes it old by mobile standards. But the hardware is still very capable.

  • SoC: Octa-core (4×2.1 GHz Cortex-A73 & 4×1.8 GHz Cortex-A53)
  • GPU: Mali‑G71 MP8
  • Memory: 4 GB DDR4
  • Storage: 64 GB internal + microSD
  • Display: 10.8″ IPS, 2560×1600 (16:10)
  • Connectivity: Wi‑Fi ac, Bluetooth 4.2, LTE (AL09)

Tools

On macOS, the simplest way to install the adb and fastboot tools is with Homebrew, which is more or less all you need. LineageOS also have a good guide on common use of the tools here.

brew install --cask android-platform-tools

Verify installation:

jeram@QL4QJP2F4N ~ % adb version       
Android Debug Bridge version 1.0.41
Version 36.0.2-14143358
Installed as /opt/homebrew/bin/adb
Running on Darwin 25.2.0 (arm64)

jeram@QL4QJP2F4N ~ % fastboot --version
fastboot version 36.0.2-14143358
Installed as /opt/homebrew/bin/fastboot

Prepare the Android device

For ADB and fastboot to communicate with the tablet, you need to enable Developer Mode.

  1. Open Settings → About tablet
  2. Tap Build number 7 times
  3. Go to Settings → Developer options
  4. Enable:
    • USB debugging
    • OEM unlocking

Connect the device to the Mac via USB, you will get a pop-up on the tablet where you need to allow the Mac or PC to connect to it. Verify connectivity:

jeram@QL4QJP2F4N ~ % adb devices
List of devices attached
8FXDU18924000194	device

Unlock the bootloader

OEMs protect devices by locking the bootloader so it can only run the vendor-designated OS. This means that we can’t install another OS on it before the bootloader is unlocked, because security? There are different procedures for getting the unlock codes. Some vendors have a service where you can request the unlock key, others simply just dont allow it and third party services have surfaced where you can pay a fee and get it done. If you search for “ministryofsolutions” you will find one of them.

I found a tool called PortatoNV. This tool can find unlock codes for some older Android devices. But it’s not supposed to be easy, you need to short a test pin on the motherboard to unlock a special serial port for the tool to use.

Opening the cmr-al09 device was fairly simple. I have an iFixit repair kit, and using the small, thin blue plastic prying tools, I slipped them in along the side of the screen to open the device. The adhesive was not as strong as I would expect.

Searched online for “cmr-al09 test point” and compared the motherboard revision to what I had. There were plenty of people showing where to find it.

You will need to power off the tablet, unplug the USB cable, short to ground for 3 seconds, plug the USB cable back in, and hold it for 2 more seconds. The tablet won’t power on, but will get into a mode where you will see a

Unfortunately, the PortatoNV tool only runs on Windows, so I found my old Windows machine, installed the tool, shortened the testpoint, and got an unknown device in Device Manager showing “USB SER”. Finding the drivers for this is another challenge…

I found the drivers online, but they’re so old they won’t run on Windows 10/11 without disabling Microsoft Defender Memory Integrity. After a lot of searching, I gave up and disabled Memory Integrity. I could then get the PortatoNV tool to find the unlock code, which only took a couple of minutes.

I could now boot the tablet again and, using ADB, put it into fastboot mode, where the firmware can be flashed.

adb reboot bootloader

Rom flashing

The XDA post offers a short, useful list of commands for flashing. Download all the files and flash them to the device. 

fastboot oem unlock <UNLOCKCODE>

The unlock command will display a prompt on the tablet, where you must confirm you want to unlock the bootloader.

fastboot flash kernel boot.img
fastboot flash recovery_ramdisk recovery.img
fastboot flash recovery_vendor recovery_vendor.img

Now you need to boot into recovery mode. I tried to do this with the power and volume+ buttons. But I could only get into the eRecovery menu. With ADB, you can also reboot it into recovery mode

adb reboot recovery

This way, I got the LineageOS recovery screen, which showed that I was corrupted and needed to be restored. There was an option to factory reset, so I did. After this, I could choose “Apply Update” in the LineageOS recovery menu. From there, you can sideload the main LineageOS zip file from the XDA forum. 

Factory reset -> Format data/factory reset
Apply update -> Apply from ADB
adb sideload lineage-20.0-20240718-RELEASE-mediapadm5wifi/lte.zip

LineageOS working

The OS is not installed and booted up – success. The next step would be to install the Google Apps suite on it to enable an app store. Root it and get SSH running so it can serve as a web server or something else useful.

As an Apple user, I wish that Apple had kind of the same tools

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Jesper Ramsgaard

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