USB Mass Storage

USB Mass Storage ArchitectureC Library to FAT File System InterfaceFAT File SystemUSB Mass Storage DriverRecommended Readings

USB Mass Storage ArchitectureC Library

usb_scsi_intfpci_scsi_intf

(not implemented)pci_atapi_intf

(not implemented)usb_atapi_intf

(not implemented)

SCSI Protocol ATAPI Protocol(not implemented)

FAT32 File System

Protocol I/O (PIO) Interface

USB Storage Driver

PCI to SCSI / ATAPIDevice Driver(not implemented)

USB Host Stack

USB SCSI FlashDrive 0

SCSI / ATAPI Drives(not supported)

USB SCSI FlashDrive x

USB ATAPIFlash Drives

(not supported)

FAT32 DriverInterface Layer

Protocol Layer

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C Library to File System Interface

• Interfaces the supported C library file I/O functions to the FAT file system and native file system.

• Supported C library file I/O functions are: mkdir, rename, remove, fopen, fclose, fread, fwrite, fseek.

• All FAT volumes are referenced with a single letter.

C Library to File System Interface – cont.

• All native file system volumes are referenced with anything other than a single letter.

• If FAT volume is drive A, do fopen(“A/dir1/dir2/filename”, “w+”)

• If native FS RAM volume is drive RAM0, do fopen(“RAM0/dir1/dir2/filename”, “w+)

FAT File System

• Sourced from HCC-Embedded in Hungary.• Supports FAT12/16/32 depending on size of the

media.• Supports long file names, multiple FAT volumes,

multiple open files per volume and is thread safe.• Features a API similar to the C library file I/O

functions, but with more functionality.

FAT File System – cont.

• The FAT file system is limited to 8.3 file names, 1 FAT volume and 1 open file per volume and is thread safe.

• FAT file system is version 2.62. Current versions have additional features such as thread context for current working directory (cwd) and a semaphore to synchronize access to each FAT volume.

USB Mass Storage Driver

• Tested with USB 2.0 and 1.1 full speed Flash memory sticks.

• Creates FAT volume on device insertion and removes FAT volume on device removal (just like Windows).

• Uses the lowest drive letter to reference the newly created FAT volume.

USB Mass Storage Driver – cont.

• Supports up to 4 devices• Driver initialization function usb_ms_init() allows

specifying event notification or polling to notify user that a device was inserted and a FAT volume was created.

Recommended Readings

• HCC-Embedded FAT12/16/32 manual in /netos/src/examples/nafatfs