File open problem(fopen and ff_fopen run different)

Hello.

I use the Code Composer Studio with AM243x EVM board.
EVM board has uSD slot.

When I use ff_fopen function to open, It is successful to read file pointer.
However, when I use the standard api fopen in the stdio.h, fopen return 0 address.

I guess wrong root makes error code, I don’t know how can I type the drive.

ff_fopen("/sd0/test.txt",“r”) was okay
fopen("/sd0/test.txt",“r”) was failed

anybody know how do I type the drive sign or root.

thank you in advance

I guess your hardware vendor supplies the standard library fopen function? You’d probably be better asking this question on their forums.