I extract two save files, one before and after buy some item.
The first with 1902 coins and the next with 1752 coins
I rename the files like Partida1.sav and Partida2.sav
after do hexdump to the files .hex the command diff should be work to make more easy the search....
root@localhost:# printf "%X\n" 1902
< 000b860 076e 0000 0000 0101 0001 0000 0000 1f03
root@localhost:# printf "%X\n" 1752
root@localhost:# diff Partida1.sav.hex Partida2.sav.hex | grep 6d8
> 0008520 0000 1111 1311 001e 06d8 0000 0000 0101
> 000b860 06d8 0000 0000 0101 0001 0000 0000 1f03
000b860 Its the Address to go, in both cases has the values
< 000b860 076e
> 000b860 06d8
BUT dont work, I use one hex - edit put FFFF in that address but in the game dont make changes, I can play it without problem
after other chages around 0008520 address the Nintendo DS show one nice BSOD... (B is for Black in this case lol)
after review the full hexcode of the save file I found something of interest
0C80 Record Deck ... 868 bytes??
0F80 Record Deck ... ""
4440 Current Deck??
54B0 1111 28 Times
6530 >>>> 28 Times
65C0 Record Deck
7AB0 1111 28 Times
8500 SYS_DT (System Data)??
A949 First Tag
B839 SYS_A (System A... )????
I found more things like replay games, system info, cards numbers etc...
When i edited around SYS_DT info the BSOD appear in the screen of the Nintendo DS.. may be exist a checksum over there
Still under Construction...