I use spi_bitbang to drive the SD card on the k210 chip development board,
referring to the content in the sam_mmcsd.c file，
The following two configuration items are opened: CONFIG_SPI_BITBANG and
CONFIG_MMCSD_SPI，After compiling, programming and starting,
you can see /dev/mmcsd0, but when you insert the sd card and execute "mount -t
vfat /dev/mmcsd0 /mnt" to mount the sd card,
the following error is reported "nsh : mount: mount failed: Function not
implemented".I want to ask my friends, is there a solution to this problem?
