operating-secure-digital-memory-cards

Example 10 – Operating Secure Digital memory cards

Secure Digital (SD) is a standard flash memory card based on the earlier Multi Media Card (MMC) standard. Similarly to the CF memory cards, the SD memory cards have a high memory capacity, up to 2GB, and have found the application in the mobile phones, MP3 players, digital cameras, and PDA computers. Access to an SD memory card is realized by using the SPI communication interface.

This example consists of several blocks that demonstrat various aspects of usage of the Mmc_Fat16 library. These are: Creation of new file and writing down to it; Opening existing file and re-writing it (writing from start-of-file); Opening existing file and appending data to it (writing from end-of-file); Opening a file and reading data from it (sending it to USART terminal); Creating and modifying several files at once; Reading file contents; Deleting file(s); Creating the swap file (see Help for details);

Fig. 13-10 Electrical connection of the SD memory card to a device from the dsPIC30F family.

program MMC_Fat16_Test

const
  SWAP_FILE_MSG as string[15] = "Swap file at: "

dim
  fat_txt as string[20]
  file_contents as string[50]

 filename as byte[14]                     ' File names

 loopP, loop2 as word
 caracter as byte
 i, size as longint

 Buffer as byte[512]

sub procedure Glob_Init
 fat_txt = "FAT16 not found"
 file_contents = "XX MMC/SD FAT16 library by Anton Rieckert" + Chr(10) + Chr(0)
 filename = "MIKRO00xTXT"             ' File names
end sub

'I-I-I--------- Writes string to USART
sub procedure I_Write_Str(dim byref ostr as byte[2])
dim  i as word
  i = 0
  while ostr[i] <> 0
    Uart1_Write_Char(ostr[i])
    Inc(i)
  wend
end sub'~


'M-M-M--------- Creates new file and writes some data to it
sub procedure M_Create_New_File
  filename[7] = "A"
  Mmc_Fat_Assign(filename, 0xA0)          ' Will not find file and then create file
  Mmc_Fat_Rewrite                         ' To clear file and start with new data
  for loopP = 1 to 99                     '  We want 5 files on the MMC card
      Uart1_Write_Char(".")
    file_contents[0] = (loopP div 10) + 48
    file_contents[1] = (loopP mod 10) + 48
'      Uart1_Write_Text(file_contents)
    Mmc_Fat_Write(file_contents, 42)      ' write data to the assigned file
  next loopP
end sub'~


'M-M-M--------- Creates many new files and writes data to them
sub procedure M_Create_Multiple_Files
  'for loop2 = "B" to "Z"
  for loop2 = "B" to "Z"
    Uart1_Write_Char(loop2)               ' signal the progress
    filename[7] = loop2                   ' set filename
    Mmc_Fat_Assign(filename, 0xA0)        ' find existing file or create a new one
    Mmc_Fat_Rewrite                       ' To clear file and start with new data
    for loopP = 1 to 44
      file_contents[0] = (loopP div 10) + 48
      file_contents[1] = (loopP mod 10) + 48
      Mmc_Fat_Write(file_contents, 42)     ' write data to the assigned file
    next loopP
  next loop2
end sub'~


'M-M-M--------- Opens an existing file and rewrites it
sub procedure M_Open_File_Rewrite
  filename[7] = "C"
  Mmc_Fat_Assign(filename, 0)
  Mmc_Fat_Rewrite
  for loopP = 1 to 55
    file_contents[0] = loopP div 10 + 64
    file_contents[1] = loopP mod 10 + 64
    Mmc_Fat_Write(file_contents, 42)      ' write data to the assigned file
  next loopP
end sub'~


'M-M-M--------- Opens an existing file and appends data to it
'               (and alters the date/time stamp)
sub procedure M_Open_File_Append
  filename[7] = "B"
  Mmc_Fat_Assign(filename, 0)
  Mmc_Fat_Set_File_Date(2005,6,21,10,35,0)
  Mmc_Fat_Append                                      ' Prepare file for append
  Mmc_Fat_Write(" for mikroElektronika 2005n", 27)   ' Write data to assigned file
end sub'~


'M-M-M--------- Opens an existing file, reads data from it and puts it to USART
sub procedure M_Open_File_Read
  filename[7] = "B"
  Mmc_Fat_Assign(filename, 0)
  Mmc_Fat_Reset(size)                     ' To read file, procedure returns size of file
  for i = 1 to size
    'Mmc_Fat_Read(caracter)
    Mmc_Fat_Read(caracter)
    Uart1_Write_Char(caracter)            ' Write data to USART
  next i
end sub'~


'M-M-M--------- Deletes a file. If file doesn't exist, it will first be created
'               and then deleted.
sub procedure M_Delete_File
  filename[7] = "F"
  Mmc_Fat_Assign(filename, 0)
  Mmc_Fat_Delete
end sub'~


'M-M-M--------- Tests whether file exists, and if so sends its creation date
'               and file size via USART
sub procedure M_Test_File_Exist(dim fLetter as byte)
dim
  fsize as longint
  year as word
  monthH, day, hourR, minuteE as byte
  outstr as byte[12]

  filename[7] = fLetter
  if (Mmc_Fat_Assign(filename, 0) <> 0) then
      '--- file has been found - get its date
    Mmc_Fat_Get_File_Date(year, monthH, day, hourR, minuteE)
    WordToStr(year, outstr)
    I_Write_Str(outstr)
    WordToStr(monthH, outstr)
    I_Write_Str(outstr)
    WordToStr(day, outstr)
    I_Write_Str(outstr)
    WordToStr(hourR, outstr)
    I_Write_Str(outstr)
    WordToStr(minuteE, outstr)
    I_Write_Str(outstr)
    '--- get file size
    fsize = Mmc_Fat_Get_File_Size
    LongIntToStr(longint(fsize), outstr)
    I_Write_Str(outstr)
  else
    '--- file was not found - signal it
    Uart1_Write_Char(0x55)
    Delay_ms(1000)
    Uart1_Write_Char(0x55)
  end if
end sub'~


'-------------- Tries to create a swap file, whose size will be at least 100
'               sectors (see Help for details)
sub procedure M_Create_Swap_File
  dim i as word

    for i=0 to 511
      Buffer[i] = i
    next i

    size = Mmc_Fat_Get_Swap_File(5000, "mikroE.txt", 0x20)
    ' see help on this function for details

    if (size <> 0) then
      LongIntToStr(size, fat_txt)
      Uart1_Write_Text(fat_txt)

      for i=0 to 4999
        Mmc_Write_Sector(size, Buffer)
        Inc(size)
        Uart1_Write_Char(".")
      next i
    end if
end sub'~


main:
'-------------- Main. Uncomment the function(s) to test the desired operation(s)
     Glob_Init
     '--- prepare PORTD for signalling
     PORTD = 0
     TRISD = 0
     ADPCFG = 0xFFFF
     '--- set up USART for the file read
     Uart1_Init(19200)
     U1MODE.10 = 1               ' clear the way for the SPI
     '--- init the FAT library
     Spi1_Init_Advanced(_SPI_MASTER, _SPI_8_BIT, _SPI_PRESCALE_SEC_1, _SPI_PRESCALE_PRI_64,
     _SPI_SS_DISABLE, _SPI_DATA_SAMPLE_MIDDLE, _SPI_CLK_IDLE_HIGH, _SPI_ACTIVE_2_IDLE)
     '--- (primary prescale = 64:1), secondary prescale = 1:1
     ' use fat16 quick format instead of init routine if a format is needed
     if (Mmc_Fat_Init(PORTF, 0) = 0) then ' EasydsPIC4 board
       Spi1_Init_Advanced(_SPI_MASTER, _SPI_8_BIT, _SPI_PRESCALE_SEC_1, _SPI_PRESCALE_PRI_4,
       _SPI_SS_DISABLE, _SPI_DATA_SAMPLE_MIDDLE, _SPI_CLK_IDLE_HIGH, _SPI_ACTIVE_2_IDLE)
       '--- Test start
       PORTD = 0x0005

       '--- Test routines. Uncomment them one-by-one to test certain features
       M_Create_New_File
       M_Create_Multiple_Files
       Uart1_Write_Char(10)

       M_Open_File_Rewrite
       M_Open_File_Append
       M_Delete_File
       M_Create_Swap_File
       Uart1_Write_Char(10)

       M_Open_File_Read
       Uart1_Write_Char(10)
       M_Test_File_Exist("F")         ' this file will not exist here
       Uart1_Write_Char(10)
       M_Test_File_Exist("B")         ' this file will exist here
       Uart1_Write_Char(10)
     else
       I_Write_Str(fat_txt)
     end if
     '--- Test termination
     PORTD = 0xFFFF

end.