Editing MMC Card Reader Development

This wiki describes the development of the [[MMC Card Reader]] Project

==Architecture==
*See [[Multi-purpose_Embedded_System#File_System | here]] for block diagram


==Development Roadmap==
===Phase 1===
*Create fatfs wrapper for file system in freertos_posix
*Use existing I2C EEPROM driver for development purpose
===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==
*[http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtmXftMXMXEVuQEcuZgVs6EVs6E666666-- SD Card connector]
*SPI interface to main board


==Software Implementation==
*Use [http://elm-chan.org/fsw/ff/00index_e.html FatFs] for accessing FAT16 file system. 
*Create a FatFs Wrapper in [http://chungyan5.no-ip.org/vc/?root=freertos_posix freertos_posix] as an intermediate layer to map API in stdio.h to API in FatFs, for example:
  +--------------------------------------------+
  | POSIX              fopen()                 |
  |                       |                    |
  |                      \|/                   |
  |                     open()                 |
  |                       |                    |
  |                      \|/                   |
  +--------------------------------------------+
  | FatFs Wrapper    fatfs_open()              |
  |                       |                    |
  |                      \|/                   |
  +--------------------------------------------+
  | FatFs              f_open()                |
  |                       |                    |
  |                      \|/                   |
  |                disk_initialize()           |
  |                       |                    |
  |                      \|/                   |
  +--------------------------------------------+
  | EEPROM         i2c_eeprom_open()           |
  +--------------------------------------------+


===Comparison of stdio and FatFs API===
*selected list for concern
{| border="1" cellspacing="0" cellpadding="5"
! Function !! stdio.h !! FatFs !! Remarks
|- 
| Open
| 
  FILE * 
[http://www.cplusplus.com/reference/clibrary/cstdio/fopen/ fopen] ( 
  const char * filename, 
  const char * mode
  
);
| 
  FRESULT 
[http://elm-chan.org/fsw/ff/en/open.html 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 ||
|-
|}
@@ Line 76: / Line 76: @@
 *stdio.h has no equivalent '''FRESULT'''
 |-
-| Read
+| Read || 7.73 || 30 ||
-|
-  size_t
-[http://www.cplusplus.com/reference/clibrary/cstdio/fread/ fread] (
-  void * ptr,
-  size_t size,
-  size_t count,
-  FILE * stream
-);
-|
-  FRESULT
-[http://elm-chan.org/fsw/ff/en/read.html f_read] (
-  FIL* FileObject,    /* Pointer to the file object structure */
-  void* Buffer,       /* Pointer to the buffer to store read data */
-  UINT ByteToRead,    /* Number of bytes to read */
-  UINT* ByteRead      /* Pointer to the variable to return number of bytes read */
-);
-|
-*'''size_t''' matches '''ByteRead'''
-*'''ptr''' matches '''Buffer'''
-*'''count''' matches '''ByteToRead'''
-*'''stream''' matches '''FileObject'''
-*stdio.h has no equivalent '''FRESULT'''
 |-
-| Write
+| Write || 7.85 || 30 ||
-|
-  size_t
-[http://www.cplusplus.com/reference/clibrary/cstdio/fwrite/ fwrite] (
-  const void * ptr,
-  size_t size,
-  size_t count,
-  FILE * stream
-);
-|
-  FRESULT
-[http://elm-chan.org/fsw/ff/en/write.html f_write] (
-  FIL* FileObject,     /* Pointer to the file object structure */
-  const void* Buffer,  /* Pointer to the data to be written */
-  UINT ByteToWrite,    /* Number of bytes to write */
-  UINT* ByteWritten    /* Pointer to the variable to return number of bytes written */
-);
-|
-*'''size_t''' matches '''ByteWritten'''
-*'''ptr''' matches '''Buffer'''
-*'''count''' matches '''ByteToWrite'''
-*'''stream''' matches '''FileObject'''
-*stdio.h has no equivalent '''FRESULT'''
 |-
-| Close
+| Close || 4.62 || 40 ||
-|
+|-
-  int
+| Seek || 4.81 || 40 ||
-[http://www.cplusplus.com/reference/clibrary/cstdio/fclose/ fclose] (
-  FILE * stream
-);
-|
-  FRESULT
-[http://elm-chan.org/fsw/ff/en/close.html f_close] (
-  FIL* FileObject     /* Pointer to the file object structure */
-);
-|
-*'''int''' matches '''FRESULT'''
-*'''stream''' matches '''FileObject'''
 |-
 |}