Had some more time to test things out. The PAP KIII files on the internal storage looked very much like the files of the Ritmix RZX-50.
@algorithm already tried to flash the firmware without success, so I tried another approach. I copied the content of the latest RZX-50 firmware (the partitions for rootfs, appfs and configfs) from here
http://prizma.bmstu.ru/~exmortis/posts/2014-10-17-rzx50-last-firmware.html and replaces the files of the PAP KIII Plus.
And success!
Of course, those two devices don't have identical hardware so I expected some errors.
What does work:
- rzx50 dmenu
- Default emulators (all systems)
- alternative emulators (all systems, did not try neogeo, I only have the fba roms)
What does not work:
- Menu for the default emulators. Start + Select gives a flashing screen instead of menu. You can't exit the default emulators
- mplayer is not working
- no radio
- volume keys (obviously) and volume in default emulators changed some times
- shutdown does not work, shows only Ritmix logo
All those bugs seem fixable in the rootfs. I currently dont't know how to proceed. I like the animations in the rzx50 dmenu, but I could replace it with my build and get the working volume keys. I don't know how to fix the default emulators, but as alternatives work great I don't see the need for it