The FatFs project homepage: http://elm-chan.org/fsw/ff/00index_e.html

This initial integration supports (only) a simple RAM disk. The FatFs source is included and pre-built, together with support for SYS/BIOS synchronization. Also included is an implementation of the "device I/O" model for the TI compiler C runtime support (RTS) library. This provides transparent support for using the C stdio.h library functions (fopen, fwrite, fclose) instead of the raw, project-specific, API functions provided by FatFs (f_open, f_write).

The configuration options initially defined here are subject to change as more device driver support is added, such as MMC/SD, SATA, and USB.

To incorporate the FatFs functionality into an application, simply "use" this module in a SYS/BIOS configuration. This will automatically generate a startup function to "plug in" the filesystem into the TI RTS, and provide the needed libraries for linking. xgconf users can simply right-click on the module icon and select "Use Module". Script users simply add a xdc.useModule("ti.sysbios.fatfs.FatFS") to their .cfg file.

There are currently three configuration options, one related to the C RTS stdio implementation, and two for the ramdisk support. First, the fatfsPrefix parameter is used as the namespace "prefix" for the C RTS fopen() function. See the TI C Compiler User's Guide (such as spru187) for more details. Basically, this prefix must be supplied as part of the filename when calling fopen(). For example, with the default value of "fat", an application would use:

  FILE * fp = fopen("fat:/signal.dat", "w");

Note the ":" as a separator. This must be part of the fopen() call, but is not specified as part of the fatfsPrefix configuration parameter.

The other parameters control how the RAM disk is configured into the system. The ramdiskSymbolName parameter can be used to specify an address of a pre-initialized (formatted) filesystem. This would be typically provided by linking in a (large) C data array. When using this parameter, the other configuration parameter, ramdiskSize, should be set to the size of the data array in units of bytes.

For example, assume a FAT filesystem that has been "serialized" into the file ramdisk.c that contains the following:

  unsigned int ramdiskData[32768] = {

then the values for these two configuration parameters should be:

  var FatFS = xdc.useModule("ti.sysbios.fatfs.FatFS");
  FatFS.ramdiskSymbolName = "ramdiskData";
  FatFS.ramdiskSize = 32768 * 4;

When the ramdiskSymbolName parameter is left "empty", .ie., "", then the ramdiskSize parameter is used to create an empty FAT filesystem at boot time of size ramdiskSize.

User Defined Hook For get_fattime()

The proper implementation of the get_fattime() function requires hardware for a real time clock. Since not all TI hardware platforms support a real time clock, the get_fattime() function will by default return a hard coded time value. However, it is possible to override this by defining a hook function instead that can be written to take advantage of a real time clock that's present. This function will then be called from get_fattime().

A hook function must be defined using the following format:

      Int32 <functionName>(Void)

Note if the user specifies a hook function in the RTSC configuration script, but does not define this function in their C code, a linker error will result.

  FILE * fp = fopen("fat:/signal.dat", "w");

  var FatFS = xdc.useModule('ti.sysbios.fatfs.FatFS");
  FatFS.getFatTimeHook = '&myTimeFxn';