kentodessa
Yeah. Factory reset did the trick.
My previous update attempts were made without KSW tools and factory reset.
I installed KSW tools recently, like 2 days ago to check what's there etc.
So...
I've prepared a 16Gb USB(FAT32) drive with all key updates for A12. Also, prepared some stuff to downgrade to A11(in case of any bad attempt) and start from scratch.
Right after factory reset the first update went successfully.
Here is my path:
A12_1.0.7Nexai -> factory reset!!! -> update to 1.2.0 non-nexai -- OK
update mcu from 220920G -> 230913G -- OK
Then
Attempt to update to 1.2.1Nexai - OK
MCU update - the same version - OK
Attempt to update to 1.4.4Nexai - OK
MCU update - no upgrade found
Attempt to update to 1.5.6Nexai - OK
MCU update - the same version - OK
A13
Attempt to update A12_1.5.6 to A13_1.1.3 - OK
MCU update - the same version - OK
Attempt to update to A13_1.4.0 - ОК
MCU update - the same version - OK
Attempt to update to A13_1.5.5 - In progress...
One thing that I noticed on
A12_1.5.6 is that the steering wheel buttons Next/Previous acts in reverse, ArrowUp - previous song, ArrowDown - next song. subject to investigate.
PS1. The boot logo and boot animation were not affected by the update procedure
PS2. You can put all updates to any folder and then just copy/paste the desired update file to the root of the USB. And not to plug/unplug your USB stick just restart the device.