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File I/O Products

smxFS™

• FS API provides the standard C library API (fopen(), fread(), fwrite(), fseek(), fclose(), etc.) to the application.
• FS Path implements the Directory Entry and FAT table structure handler. It supports FAT12/16/32 and VFAT.
• FS Mount implements the mount, unmount, and format functions for inserted devices.
• FS Cache implements the Cache for Data, FAT, and Directory entries.
• FS Driver Interface integrates all of the devices into the file system via a unique interface.
• FS Port implements the OS and Compiler related definitions, macros, and functions.
• FS Utility implements check disk and fix functions.

ATA

Supports basic operations.
 

CompactFlash

Supports memory mode.
 

DiskOnChip®

Based on TrueFFS v6.x and supports G3/P3, G4, and H1 families.
 

MMC/SD

Supports 4-bit bus and SPI.
 

NAND

See smxFFS datasheet.
 

NOR

See smxFD datasheet. Not intended for frequent modification of files or logging. Instead use NAND flash or smxFLog.
 

RAM Disk

Included.
 

USB

See smxUSBH datasheet.
 

Windows

Allows running smxFS under Windows, which may be helpful during development. Included with smxSim and standalone (non-SMX) orders.

Porting Layer

Two files, fport.h and fport.c, contain definitions, macros, and functions to port smxFS to any OS, compiler, and processor. Currently, they support SMX®, Windows, and Linux.

Configuration

smxFS has a simple configuration file, fcfg.h, to allow setting preferences and tuning RAM and ROM requirements. Cache characteristics can be set to control RAM usage. Some options can be disabled to reduce code usage, such as FAT32, VFAT, and write support.

16-Bit Addressing Support

smxFS supports processors that can only do 16-bit memory addressing  (not byte addressing) such as the TI TMS320C55xx DSPs. These processors are difficult to support because of byte data and byte fields in standard data structures. This is enabled by a configuration option in smxFS.

Safety

The DOS/Windows FAT file system is inherently not power fail safe, so smxFS implements features to compensate for this:

1. sfs_chkdsk() API can check and fix many problems, such as cross-linked files, lost chains, bad directory entries, and other problems. Flags specify which types of problems to fix (or none). It indicates the results using flags in the return value and can give detailed text information in a buffer, to allow a human operator to correct problems. Please see the smxFS User’s Guide for details.
2. Clean shutdown checking determines whether all files were closed and caches flushed before the system shut down. If not, sfs_chkdsk() should be called.

1. Unused API functions are dead-stripped by the linker, so the size used by your application is likely to be much smaller.
2. Reduced size is with SFS_READONLY enabled and SFS_FULL_FEATURES_SUPPORT disabled.
3. The NOR flash driver code is part of smxFD. It includes two layers, STL and HIL. HIL is used to port to different hardware and flash chips so the size can vary widely. The above size is for the Intel 28F128K3 StrataFlash NOR flash chip.
4. The USB disk driver code is part of smxUSBH. The size can vary widely depending upon which Host Controller driver you are using. The size above includes the ISP1362 driver. See the smxUSBH brochure for other sizes.
5. Driver sizes vary because they have porting code that varies for different hardware.
6. Minimum cache + stack sizes. See discussion above table.

1. MMC/SD bus mode times were measured using DMA.
2. MMC/SD SPI times were measured using polling, which is the best case.
3. Measured using Sandisk 256 MB, Ultra II 512 MB, and 1 GB SD cards.
4. Measured using Sandisk Extreme III 2 GB SD card.
5. NOR flash times are for Intel 28F128K3 StrataFlash on MCF5485EVB.
6. USB times vary significantly depending on the controller, as the examples show. See the Performance section of the smxFS User’s Guide for details. Also see the smxUSBH brochure.

Cache Sizes vs. Performance

The size of caches affects the performance. The following graph shows the performance of a USB flash disk reading/writing operation when the cache sizes are set to different values. See the smxFS User’s Guide for more graphs for different hardware.

LPC2468EA OEM Board 72MHz (USB OHCI):  click here for graph


Features Omitted from the Lite Version

smxFS Lite omits advanced features to reduce memory footprint and save cost. It is a subset of the same codebase as the full version. The Lite version has the following limitations:

• Long File Name support is omitted. You must use 8.3 format names to access files and paths.
• FAT32 is disabled by default but you can set SFS_FAT32_SUPPORT to 1 to enable it again.
• Current Working Directory is disabled. You must use full path names such as A:\\dir\\subdir\\file1 to access files. Related APIs are omitted from the source code.
• The following APIs are omitted:
  • chkdsk()
  • findfirst()/findnext()/findclose()
  • rename()
  • setprop()/getprop()/stat()/chmod()/timestamp()
  • setvolname()/getvolname()
    
• The following APIs are disabled by default:
  • mkdir()/rmdir(). Can enable by setting SFS_MKDIR_SUPPORT to 1.
  • format()/partition(). Can enable by setting SFS_FORMAT_SUPPORT to 1. These functions are provided primarily to support fixed media, since removable media are preformatted and can be reformatted on a PC.
    

• Access the manual.
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