Hello Dhanuja,
I believe you want to write or read raw video data into the SD card.
Can you just confirm this?
As I already mentioned in my first response, you will have to implement FatFS on the FX3S side such that the data that is being written is not in RAW format and gets written or read in a format that the PC can recognize.
You can go through the functions that are available in FatFS file system from the link: FatFs - Generic FAT Filesystem Module
The above link addresses the list of functions that can be implemented in a file system.
Please go through it to get a better idea and understanding of how you can do it.
Regards,
Yashwant
