Reading of file, stored in FAT fs, has tested for large files upto some MiB.
Writing of file into the USB flash drive succeeded. But due to certain restrictions on pf_write() of PFF library, write operations are in limit. To know the limitation please visit Petit FATfs manual webpage of pf_write().
Debug macros added. For ignoring the program's logging printfs. Also, the directory opening function pf_opendir is tested with pf_readdir.
Kernel driver reattach error resolved.