SD Card Access

Files may be written to and read from an SD card. This is typically used for storing a firmware image for Recovery Mode.

To use an SD card on the controller:

1. Ensure that the SD card is inserted.
2. Mount the card using SD_MOUNT.
3. Ensure the card is accessible using SD_ISREADY before performing a read or write action.
4. Unmount the card, if desired, using SD_UNMOUNT after performing read/write actions.