I saw a few people asking about it but the only solutions I saw seemed cumbersome and involved file name conversions etc.
Here's what I did:
- Install SAMBA Filesharing from Marketplace on your Play and make sure it is active
- Map your SD card to your PC as a network drive (you can just type \\Android into explorer)
- Using your PC open the newly mapped Android SD card and create a text file wherever you want the memory card to be
- Rename it to MSD001.MCD (selecting 'all files' in the save as process so it becomes an MCD file, not a TXT)
- Configure PCSX to use that memory card file (Configuration > Memory Cards... > Select Mcd)
- Launch a new game and get to a position where you can save it (I used FFVIII)
- Load up FPSE on your Android
- Under 'Settings > MISC > Select memcard 1' point it to the memory card file you created
- Launch your game and get to a point where you can load a game then select memory card 1
- Hopefully your game should then load the exact same save that you created on your PC.
I've tested it using FFVIII only but it worked both ways, which is to say a save from FPSE opened in PCSX and the save from PCSX opened on the FPSE.
An even better way of doing this, for true portability, would be if you could set your Dropbox folder as the home of the memory card but I believe the Dropbox heirarchy is not (any longer) navigable on Android. If I'm wrong please let me know.
I will look into the possibility of doing this with savestates but am assuming it's more complicated.