I got the small servo and it uses an "ATMEL SAMD10U 822B TW 18224YS" main board (looks like "SAM D10D 24-pin QFN" to me from the datasheet) and the chip on the back side is an "MPJJ 6515 800". But I could not find any datasheet.
SAM D10 datasheet pinout:
At the side of the board is written: " 2KG_D10YS_V0_04 PCB".
Sharing some new pictures here:
I'm reverse engineering the circuit to see if we can work with it.
Future work, check the compatibility with this codes:
Codes of the findings above can be found here: