MMC Card Reader Development

This wiki describes the development of the MMC Card Reader Project

Architecture

• See here for block diagram

Development Roadmap

Phase 1

• Create stdio.h wrapper for file system in freertos_posix
• Use existing I2C EEPROM driver for development

Phase 2

• Circuit design for interfacing MMC

Phase 3

• SPI driver for MMC

Phase 4

• Test for normal read/write function
• hotswap (should not hang or cause voltage dip)
• multiple file read/write (protection)

Circuit and PCB

• SD Card connector
• SPI interface to main board

Software Implementation

• Use FatFs for accessing FAT16 file system.
• Create a stdio.h wrapper for freertos_posix

Comparison of FatFs and stdio API

• selected list is described below

Comparison between FatFs and stdio API

Function	stdio.h	FatFs	Remarks
Open	FILE * fopen ( const char * filename, const char * mode );	FRESULT f_open ( FIL* FileObject, /* Pointer to the blank file object structure */ const XCHAR* FileName, /* Pointer to the file neme */ BYTE ModeFlags /* Mode flags */ );	FILE matches FIL filename matches FileName mode matches ModeFlags stdio.h has no equivalent FRESULT
Read	7.73	30
Write	7.85	30
Close	4.62	40
Seek	4.81	40