Reading data from bluetooth LCD tablet

Hi,

I recently bought a NewYes LCD tablet that is advertized with  
Android/Windows/MacOS software only, but can still act as an excellent  
(and cheap) graphics tablet under Linux, check
     
https://www.banggood.com/NEWYES-10inch-Bluetooth-Archive-Synchronize-Writing-Tablet-Save-Drawing-LCD-Office-Family-Graffiti-Toy-Gift-p-1446888.html?cur_warehouse=CN

I succeeded in writing a rather simple user space driver for the  
tablet connected with the USB cable, using libusb.
The code is available as newyes_tablet_driver.tar.bz2 on
     https://sourceforge.net/projects/sf-xpaint/files/deskwrite/

However, the constructor does not provide any technical information  
about the bluetooth settings (just proprietary binary code, see  
http://9612.myvsoncloud.com/). The device is seen as

bd-address: FF:FF:05:00:1C:02
name: VSON#WP9612#000000
[CHG] Device FF:FF:05:00:1C:02 UUIDs: 00001800-0000-1000-8000-00805f9b34fb
[CHG] Device FF:FF:05:00:1C:02 UUIDs: 00001801-0000-1000-8000-00805f9b34fb
[CHG] Device FF:FF:05:00:1C:02 UUIDs: 0000fff0-0000-1000-8000-00805f9b34fb

Pairing in a standard way does not work, neither under Linux nor  
Windows, although the Android "e-Draw" app provided by the constructor  
(http://www.vson.com.cn/English/html/9571303320.html) seems to provide  
such a pairing - pairing from the Android bluetooth stack itself does  
not work either.

Is there any reasonable way to reverse-engineer this stuff in the  
absence of response from VSON at this date ? I would content myself  
with the USB connection, but it seems that the data recorded by the  
tablet are available only under bluetooth - they are not obviously  
visible via the usb connection. Worse, the vector data input do not  
seem to be accessible by bluetooth via e-Draw, just png images, which  
is really not a very smart idea.

Being locked by such proprietary policies would be really shameful ...

Many thanks in advance,
Jean-Pierre Demailly