30 Dec 2023

Laser MID-787 – CFW

Laser MID-787 is a model title for a family of cheap and bad Chinese tablets.

Luckily, Laser MID-787 can be unlocked thanks to efforts on another Chinese tablet that was sold in Ukraine circa 2018.

These Chinese tablets the following in common:

Bad screen quality with horrible angles.
- Screen size: 7", 8", or 10.1".
- Screen resolution’s longest axis is equal to 1024 or 1280.
- Often (not always) mathematically bad 16:9 / 16:10 ratio implementation, such as 1024x600 (600*16/9=1066⅔).
SIM-card slot
Internal PCB markings with K706 (or ∂erivatives, e.g. K706x)
MediaTek (MTK) CPU of MTK 8321 (MTK 6580)

K706

Unfortunately, I lost my PCB photos. However, the PCB looks like this,


“K706B” on yellow label upside down source (ar)	k706 (almost certainly the same PCB without battery!) source: prom.ua.

Other known K706 (K706x) family tablets,

BRAVIS NB85
Bravis NB753
Digma CITI 7591 3G
Ergo Tab A710 3G
Krono 7031
Laser MID-787
NAVITEL T707 3G
NAVITEL T500 3G Auto
CTRONIQ Snook X75

Prerequisites

Windows computer
Laser MID-787 (or compatible clone)
USB cable

Downloads

MTK Android Driver All-in-One
SP Flash Tool v5.1540, v5.1916, or newer – either standalone (use GSM forums) or within official MID-787 Firmware Update
Older 7.0_MT8321_K706.N0.V10.8.CQ-V07.2493 firmware (~1GB compressed/~2GB uncompressed) – Firmware247 (leads to GDrive, password: https://firmware247.com ) / archive.org (no password) – comes with SCATTER
Model: LASER MID-787 Os : Android 7.0 Language support: Multilang
Bravis NB753 custom TWRP recovery (transplanted from yet another tablet) – by coditnets.
Transplanted recovery.img only works in landscape mode. Otherwise, works OK.
K706.N0.V10.8.CQ-V07.2493-GMS – Patched LittleKernel (LK.bin) – Produced by me
Download latest Magisk .APK

Explanation

SP Flash Tool, by default, performs a cyclic redundancy check, so CRC check information has to be adjusted or disabled.
Transplanted recovery.img for Bravis NB753 only works on Laser MID-787 in landscape mode. Otherwise, works OK.
Trivia: BRAVIS NB753 specs on Rozetka ua, and it is too old to be sold.
For Laser MID-787: LittleKernel (LK.bin) has to be patched. Otherwise, LK.bin prevents tablet from booting with
- LK.bin does not seem to be transplantable or otherwise interchangeable from other k706 tablets, because LK.bin also contains compiled individual drivers. So, stock LK.bin from 7.0_MT8321_K706.N0.V10.8.CQ-V07.2493 had to be patched.

Why older Laser MID-787 firmware?

The reason the older Laser MID-787 firmware is recommended deserves a dedicated section. I believe that changes across firmware builds may demonstrate that Laser is involved in anti-consumer practices,

Comparison can be seen below, better aspects are highlighted,

≡	Laser’s official “MID-787 Firmware Update”	`7.0_MT8321_K706.N0.V10.8.CQ-V07.2493`
Android OS Version	Android 10 (Go)	Android 7
Google SafetyNet Attestation	Pass	Pass
Display driver	Horrible, even with customisations. Graphical glitches, such as flickering dots across screen, do occur.	Noticeably better, even on bad display. Likely shows that “official” firmware uses incorrect driver.
GApps	Present, Google Go-based (tight coupling with Google Play Services, much slower on slow CPU!)	Present, minimal and AOSP-based (little/no coupling with Google Play Services)
Speed	Horrible. The firmware comes with built-in RAM optimizer that barely helps (likely due to reasons above)	Fair
fastboot (bootloader) interface	Functionality is broken (always “USB Device Not Recognized”, jeopardising repairability!)	Works as expected
`fastboot oem unlock`	Broken, because fastboot is broken!	Works as expected
Overall customisability and experience	Painful	Not great, but more acceptable

Guide

Getting started

Download everything
Charge up tablet to at least 50%.
In K706.N0.V10.8.CQ-V07.2493-GMS folder, open Checksum.ini. In IsEnableChecksum section, change CHECKSUM_SWITCH to 0.
- Alternatively, you may opt to keep file as is, and keep adjusting checksums in this file, as SP Flash Tool informs you of checksum errors. This option is safer, but more tedious.
Open SP Flash Tool.

In SP Flash Tool

Ensure Download tab is selected.
For Scatter-loading file, select MT6580_Android_scatter.txt from 7.0_MT8321_K706.N0.V10.8.CQ-V07.2493. The flasher program will load for ~10-20 seconds.
Once loaded, in drop down menu below, pick Format All + Download (being cleanest option) or Download Only (often recommended option)
In spreadsheet below,
- For name lk, select custom lk.bin
- For name recovery, select custom recovery.img
Click and thus toggle green “Download” button.

Flashing process

Ensure tablet is fully turned off.
- If you disassembled the tablet, then next to power button, there is a normally inaccessible, tiny RESET button/switch. This button/switch can be pressed with a tiny flathead screwdriver, and it shuts off power from the CPU, halting its operations.
Once green “Download” button is clicked on SP Flash Tool, connect tablet to the computer without pressing any buttons on the tablet. The computer should recognise the tablet and begin flashing.
- Sometimes, computer does not recognise in time or hangs, and the tablet boots normally. If this happens, simply turn off tablet again and try again. I had to try at least 3 times before I was successful.
Wait until the flashing process is complete. SP Flash Tool will inform you by,
Disconnect tablet from the computer.
Either connect the tablet back, or turn the tablet to the computer, causing its hardware to initiate.

First boot

You will boot into Android 7.

Go through first-run stage.

Copy files

Copy Magisk-*.apk to the tablet.
Make another of the said Magisk-*.apk, name it Magisk-*.apk.zip. It will be used for rooting process

Root

Reboot into recovery

Enable “Developer Mode”
Enable “adb” interface
Connect to computer
Authorise “adb” connection signature from the computer,
Run

adb reboot recovery

Note: fastboot oem unlock should not be required with custom lk.bin.

In TWRP recovery

Note: Transplanted TWRP only works on Laser MID-787 in landscape mode. Otherwise, works OK.

Flash Magisk-*.apk.zip
(Optionally) flash any other desired tweaks
Reboot to Android

In Android

Magisk-*.apk.zip will install temporary su, but it will not install Magisk app (APK) itself. Therefore, use AOSP file manager to install Magisk APK.

Connect to the internet.

After Magisk app is installed, run it. It will complain of the “incomplete installation” and suggest options to fix this. Simply go through its default options. Magisk will require at least 2 reboots, and this is normal. After a few reboots, you will have fully rooted tablet.

Optional – Delete GApps and further customise

Unlike on official Android 10, display does not need to be adjusted to be usable.

There is nothing extraordinary about this step. I do not recommend any “GApps remover” scripts, as they (as of 2023) do not verify what they are deleting. As such, I recommend using any common Root-based app manager, such as Titanium Backup and your brain, to delete unwanted GApps.

At this point, you fully unlocked, rooted, and customised your Laser MID-787. Congratulations!

Tim Abdiukov