Hello,
I try to use FATFS library on the PIC18lf46k80 with external 8MHz, but f_mount(&FatFs,"",1) don't return FR_OK. Can you tell me if this program works for you?
I don't know if problem is with software or hardware.
I use SSD1298 so connection should be right but, there are not a few resistor there.
I don't know anyting of the library you are using, but I would recommend starting with the FAT16 formatting just due to the back compatibility that is available for these libraries; The eFAT is a more recent kind which perhaps is not compatible with all these libraries.