I am not sure if it is a bug or my mistake so I post it here.
I added a category on my additional USB drive like things below:
<system>
<name>psp_sample</name>
<fullname>Playstation Portable Sample</fullname>
<manufacturer>Sony</manufacturer>
<release>2004</release>
<hardware>portable</hardware>
<path>/storage/roms/psp_sample</path>
<extension>.iso .ISO .cso .CSO .pbp .PBP</extension>
<command>emuelecRunEmu.sh %ROM% -P%SYSTEM% --core=%CORE% --emulator=%EMULATOR% --controllers="%CONTROLLERSCONFIG%"</command>
<platform>psp</platform>
<theme>psp_sample</theme>
<emulators>
<emulator name="PPSSPPSDL">
<cores>
<core default="true">PPSSPPSDL</core>
</cores>
</emulator>
<emulator name="libretro">
<cores>
<core>ppsspp</core>
</cores>
</emulator>
</emulators>
</system>
And while I run the libreretro:PPSSPP,it runs into a black screen.And when I check the log It say a file cannt read.
I put the same CSO disk file on the default “psp” folder every thing goes well.