fix(SDHC)!: Fix SDHC Formats Card Size Incorrectly, Update FatFS to R0.15, Add SDXC and exFAT Support

[Jake-Carter]

Description

Bug fix

The SDHC_FAT example would format cards incorrectly. For a 32GB card, the library would format it with a card size of 1.8GB. This was caused by an integer overflow error in the native SDHC library implementation (fixed in 9771dcc)

FatFS Version Upgrade

I aded support for R0.15 of the FatFS library. This has some potentially relevant bug fixes (see change notes).

The default version is still R0.13, but will be updated to R0.15 next release. Users can upgrade now by setting the FATFS_VERSION build configuration variable to ff15.

FatFS R0.15 changed the input parameters for f_mkfs to acccept a format struct.
Users upgrading from R0.13/R0.14 -> R0.15 can make the following change to the f_mkfs function.

-    if ((err = f_mkfs("", FM_ANY, 0, work, sizeof(work))) !=
+    MKFS_PARM format_options = {
+        .fmt = FM_ANY
+    };
+
+    if ((err = f_mkfs("", &format_options, work, sizeof(work))) !=
         FR_OK) {
         printf("Error formatting SD card: %s\n", FF_ERRORS[err]);
     }

Alternatively, users can set the new FATFS_VERSION build configuration variable to ff13 or ff14 to keep using the old versions for their project.

# Enable SDHC library
LIB_SDHC = 1
# Use FatFS R0.13
FATFS_VERSION = ff13

SDXC and exFAT Support

The ff15 configuration now enables SDXC support out of the box. This enables larger card sizes.

exFAT support requires LFN (Long File-Name Support), which requires unicode support. This increases the library size significantly. I'm open to suggestions on how to deal with it. Should we provide a mechanism for easily toggling SDXC support? Or just rely on the user to edit ffconf.h as needed?

arm-none-eabi-size FAT32.a
   text    data     bss     dec     hex filename
    562       0       5     567     237 diskio.o (ex FAT32.a)
  19307       0    1127   20434    4fd2 ff.o (ex FAT32.a)
      0       0       0       0       0 ffsystem.o (ex FAT32.a)
  60150       0       0   60150    eaf6 ffunicode.o (ex FAT32.a)
    542       4       0     546     222 board.o (ex FAT32.a)
    178       0       0     178      b2 stdio.o (ex FAT32.a)
    327       0       0     327     147 led.o (ex FAT32.a)
   1381       0      17    1398     576 mx25.o (ex FAT32.a)
    777       0       0     777     309 pb.o (ex FAT32.a)
    666       0       0     666     29a sharp_mip.o (ex FAT32.a)

Testing

I tested the SDHC_FAT example on the MAX32666FTHR, MAX32666EVKIT, and MAX78002EVKIT to validate the native SDHC implementation.

• : ATP 8GB SDHC (Speed Class 10)
• : SanDisk Ultra 16GB SDHC (Speed Class 10)
• : SanDisk Ultra 32GB SDHC (Speed Class 10)
• : Amazon Basics 128GB SDXC (Speed Class 10)

Checklist Before Requesting Review

• PR Title follows correct guidelines.
• Description of changes and all other relevant information.
• (Optional) Link any related GitHub issues using a keyword
• (Optional) Provide info on any relevant functional testing/validation. For API changes or significant features, this is not optional.