This page is dedicated to the design of code that allows access to an IDE Hard Disc which is formatted with the FAT32 file system. The code was designed to run on an Atmega AVR MCU but will probably port to others easily as it is written in standard C. This library will allow files and directories to be accessed, and builds upon the IDE Device Driver.

FAT32 Interface Layer Block Diagram

The FAT32 global structure is used to store global variables which relate to the location of FAT32 partition, also contains the LFN text buffer. The FAT32 definitions are used where constants are needed to refer to either types of files, and file structures.
The FAT32_Base functions provide need interaction with the lower IDE Device Driver layer, and perform tasks such as File Allocation Table traversing, LBA to Cluster number conversion, etc.
The FAT32_Access library is used by higher level routines such as directory browsing, file reading, and FAT32 initialisation. There should be no need for other functions outside the FAT32_Access library to directly use the FAT32_Base rountines.

Example

byte ReadData(UI32 startcluster, UI32 bytenum)
{
// Convert bytenum into a sector to read
sector = bytenum / 512;
// Convert bytenum and sector into an offset in current sector buffer
offset = bytenum - (sector*512);
// Read file sector
FAT32_SectorReader(startcluster, sector);
// Extract byte from sector read
bytedata = IDE_SectorByte(offset);
// Return data found
return bytedata;
}