Connect Memory Card using PIC18F4520 Code




The Multi Media Card (MMC) is a Flash memory card standard. MMC cards are currently available in sizes up to and including 32 GB and are used in cellular phones, digital audio players, digital cameras and PDA’s.
mikroC PRO for PIC provides a library for accessing data on Multi Media Card via SPI communication. This library also supports SD (Secure Digital) and high capacity SDHC (Secure Digital High Capacity) memory cards .

Secure Digital Card

Secure Digital (SD) is a Flash memory card standard, based on the older Multi Media Card (MMC) format.
SD cards are currently available in sizes of up to and including 2 GB, and are used in digital cameras, digital camcorders, handheld computers, media players, mobile phones, GPS receivers, video games and PDAs.

Secure Digital High Capacity Card

SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard which increases card’s storage capacity up to 32 GB by using sector addressing instead of byte addressing in the previous SD standard.
SDHC cards share the same physical and electrical form factor as older (SD 1.x) cards, allowing SDHC-devices to support both newer SDHC cards and older SD-cards. The current standard limits the maximum capacity of an SDHC card to 32 GB.Connect Memory Card using PIC18F4520 Code

  Important :

  • Routines for file handling can be used only with FAT16 file system.
  • Library functions create and read files from the root directory only.
  • Library functions populate both FAT1 and FAT2 tables when writing to files, but the file data is being read from the FAT1 table only; i.e. there is no recovery if the FAT1 table gets corrupted.
  • If MMC/SD card has Master Boot Record (MBR), the library will work with the first available primary (logical) partition that has non-zero size. If MMC/SD card has Volume Boot Record (i.e. there is only one logical partition and no MBRs), the library works with entire card as a single partition. For more information on MBR, physical and logical drives, primary/secondary partitions and partition tables, please consult other resources, e.g. Wikipedia and similar.
  • Before write operation, make sure you don’t overwrite boot or FAT sector as it could make your card on PC or digital camera unreadable. Drive mapping tools, such as Winhex, can be of a great assistance.
  • Library uses SPI module for communication. The user must initialize the appropriate SPI module before using the MMC Library.
  • For MCUs with multiple SPI modules it is possible to initialize all of them and then switch by using the SPI_Set_Active() function. See the SPI Library functions.
  • MMC FAT 16 Library works with PIC18 family only.

The SPI module has to be initialized through SPIx_Init_Advanced routine with the following parameters:

  • SPI Master
  • Primary prescaler 64
  • Data sampled in the middle of data output time
  • Clock idle low
  • Serial output data changes on transition form low to high edge
  Tip : Once the MMC/SD card is initialized, SPI module can be reinitialized at higher a speed. See the Mmc_Init and Mmc_Fat_Init routines.

External dependencies of MMC Library

The following variable must be defined in all projects using MMC library: Description : Example :
extern sfr sbit Mmc_Chip_Select; Chip select pin. sbit Mmc_Chip_Select at RC0_bit;
extern sfr sbit Mmc_Chip_Select_Direction; Direction of the chip select pin. sbit Mmc_Chip_Select_Direction at TRISC0_bit;

Library Routines

  • Mmc_Init
  • Mmc_Read_Sector
  • Mmc_Write_Sector
  • Mmc_Read_Cid
  • Mmc_Read_Csd
  • Mmc_Multi_Read_Start
  • Mmc_Multi_Read_Sector
  • Mmc_Multi_Read_Stop

Routines for file handling:

  • Mmc_Fat_Init
  • Mmc_Fat_QuickFormat
  • Mmc_Fat_Assign
  • Mmc_Fat_Reset
  • Mmc_Fat_Read
  • Mmc_Fat_Rewrite
  • Mmc_Fat_Append
  • Mmc_Fat_Delete
  • Mmc_Fat_Write
  • Mmc_Fat_Set_File_Date
  • Mmc_Fat_Get_File_Date
  • Mmc_Fat_Get_File_Date_Modified
  • Mmc_Fat_Get_File_Size
  • Mmc_Get_File_Write_Sector
  • Mmc_Fat_Get_Swap_File
  • Mmc_Fat_Tell
  • Mmc_Fat_Seek
  • Mmc_Fat_Rename
  • Mmc_Fat_MakeDir
  • Mmc_Fat_RenameDir
  • Mmc_Fat_RemoveDir
  • Mmc_Fat_ChangeDir
  • Mmc_Fat_Exists
  • Mmc_Fat_Dir
  • Mmc_Fat_ReadDir
  • Mmc_Fat_Activate
  • Mmc_Fat_ReadN
  • Mmc_Fat_Open
  • Mmc_Fat_Close
  • Mmc_Fat_EOF

Mmc_Init

Prototype unsigned char Mmc_Init();
Returns
  • 0 – if MMC/SD card was detected and successfully initialized
  • 1 – otherwise
Description Initializes MMC through hardware SPI interface.
Mmc_Init needs to be called before using other functions of this library.
Requires The appropriate hardware SPI module must be previously initialized.
Global variables :

  • Mmc_Chip_Select: Chip Select line
  • Mmc_Chip_Select_Direction: Direction of the Chip Select pin

must be defined before using this function. The appropriate hardware SPI module must be previously initialized. See the SPI1_Init, SPI1_Init_Advanced routines.

Example
// MMC module connections 
sfr sbit Mmc_Chip_Select at RC0_bit;
sfr sbit Mmc_Chip_Select_Direction at TRISC0_bit;
// MMC module connections
...
SPI1_Init();

error = Mmc_Init();  // Init with CS line at RC0_bit

Mmc_Read_Sector

Prototype unsigned char Mmc_Read_Sector(unsigned long sector, char *dbuff);
Returns
  • 0 – if reading was successful
  • 1 – if an error occurred
Description The function reads one sector (512 bytes) from MMC card.
Parameters:

  • sector: MMC/SD card sector to be read.
  • dbuff: buffer of minimum 512 bytes in length for data storage.
Requires MMC/SD card must be initialized.
Example
// read sector 510 of the MMC/SD card
unsigned int error;
unsigned long sectorNo = 510;
char dataBuffer[512];
...
error = Mmc_Read_Sector(sectorNo, dataBuffer);

Mmc_Write_Sector

Prototype unsigned char Mmc_Write_Sector(unsigned long sector, char *dbuff);
Returns
  • 0 – if writing was successful
  • 1 – if there was an error in sending write command
  • 2 – if there was an error in writing (data rejected)
Description The function writes 512 bytes of data to one MMC card sector.
Parameters:

  • sector: MMC/SD card sector to be written to.
  • dbuff: data to be written (buffer of minimum 512 bytes in length).
Requires MMC/SD card must be initialized.
Example
// write to sector 510 of the MMC/SD card
unsigned int error;
unsigned long sectorNo = 510;
char dataBuffer[512];
...
error = Mmc_Write_Sector(sectorNo, dataBuffer);

Mmc_Read_Cid

Prototype unsigned char Mmc_Read_Cid(char *data_cid);
Returns
  • 0 – if CID register was read successfully
  • 1 – if there was an error while reading
Description The function reads 16-byte CID register.
Parameters:

  • data_cid: buffer of minimum 16 bytes in length for storing CID register content.
Requires MMC/SD card must be initialized.
Example
unsigned int error;
char dataBuffer[16];
...
error = Mmc_Read_Cid(dataBuffer);

Mmc_Read_Csd

Prototype unsigned char Mmc_Read_Csd(char *data_csd);
Returns
  • 0 – if CSD register was read successfully
  • 1 – if there was an error while reading
Description The function reads 16-byte CSD register.
Parameters:

  • data_csd: buffer of minimum 16 bytes in length for storing CSD register content.
Requires MMC/SD card must be initialized.
Example
unsigned int error;
char dataBuffer[16];
...
error = Mmc_Read_Csd(dataBuffer);

Mmc_Multi_Read_Start

Prototype unsigned int Mmc_Multi_Read_Start(unsigned long sector);
Description The function starts multi read mode, sectors are sequentially read starting from the sector given in the function argument.
Parameters
  • sector: starting sector number.
Returns
  • 0 – if multi read start was successful.
  • 1 – ir error occured.
Requires MMC/SD card must be initialized.
Example
unsigned int error;
char sector;
...
error = Mmc_Multi_Read_Start(sector);
Notes None.

Mmc_Multi_Read_Sector

Prototype void Mmc_Multi_Read_Sector(char *dbuff);
Description The function reads sectors in multi read mode and places them in the buffer given as the function argument. Next function call reads the subsequent sector. Buffer size should be 512B.
Parameters
  • dbuff: buffer for holding the sector data.
Returns Nothing.
Requires MMC/SD card must be initialized.
Example
unsigned int error;
...
Mmc_Multi_Read_Sector(buffer);
Notes None.

Mmc_Multi_Read_Stop

Prototype unsigned int Mmc_Multi_Read_Stop();
Description The function stops multi read mode sequence.
Parameters None.
Returns
  • 0 – if stop was successful.
  • 1 – ir error was detected.
Requires MMC/SD card must be initialized.
Example
Mmc_Multi_Read_Stop;
Notes None.

Mmc_Fat_Init

Prototype unsigned short Mmc_Fat_Init();
Returns
  • 0 – if MMC/SD card was detected and successfully initialized
  • 1 – if FAT16 boot sector was not found
  • 255 – if MMC/SD card was not detected
Description Initializes MMC/SD card, reads MMC/SD FAT16 boot sector and extracts necessary data needed by the library.

  Note : MMC/SD card has to be formatted to FAT16 file system.
Requires Global variables :

  • Mmc_Chip_Select: Chip Select line
  • Mmc_Chip_Select_Direction: Direction of the Chip Select pin

must be defined before using this function. The appropriate hardware SPI module must be previously initialized.

Example
// MMC module connections 
sfr sbit Mmc_Chip_Select at RC0_bit;
sfr sbit Mmc_Chip_Select_Direction at TRISC0_bit;
// MMC module connections

// Initialize SPI1 module
SPI1_Init_Advanced(_SPI_MASTER_OSC_DIV64, _SPI_DATA_SAMPLE_MIDDLE,_SPI_CLK_IDLE_LOW, _SPI_LOW_2_HIGH);

// use fat16 quick format instead of init routine if a formatting is needed
if (!Mmc_Fat_Init()) {
// reinitialize SPI1 at higher speed
SPI1_Init_Advanced(_SPI_MASTER_OSC_DIV4, _SPI_DATA_SAMPLE_MIDDLE, _SPI_CLK_IDLE_LOW, _SPI_LOW_2_HIGH);
...
}

Mmc_Fat_QuickFormat

Prototype unsigned char Mmc_Fat_QuickFormat(char *mmc_fat_label);
Returns
  • 0 – if MMC/SD card was detected, successfully formated and initialized
  • 1 – if FAT16 format was unsuccessful
  • 255 – if MMC/SD card was not detected
Description Formats to FAT16 and initializes MMC/SD card.
Parameters:

  • mmc_fat_label: volume label (11 characters in length). If less than 11 characters are provided, the label will be padded with spaces. If null string is passed volume will not be labeled

  Note :

  • This routine can be used instead or in conjunction with Mmc_Fat_Init routine.
  • If MMC/SD card already contains a valid boot sector, it will remain unchanged (except volume label field) and only FAT and ROOT tables will be erased. Also, the new volume label will be set.
Requires The appropriate hardware SPI module must be previously initialized.
Example
// Format and initialize MMC/SD card and MMC_FAT16 library globals
if (!Mmc_Fat_QuickFormat(&mmc_fat_label)) {
...
}

Mmc_Fat_Assign

Prototype unsigned short Mmc_Fat_Assign(char *filename, char file_cre_attr);
Returns
  • 2 – if there are no more free file handlers, currently opened file is closed in order to free space.
  • 1 – if file already exists or file does not exist but a new file is created.
  • 0 – if file does not exist and no new file is created.
Description Assigns file for file operations (read, write, delete…). All subsequent file operations will be applied on an assigned file.
Parameters:

  • filename: name of the file that should be assigned for file operations. File name should be in DOS 8.3 (file_name.extension) format. The file name and extension will be automatically padded with spaces by the library if they have less than length required (i.e. “mikro.tx” -> “mikro .tx “), so the user does not have to take care of that. The file name and extension are case insensitive. The library will convert them to proper case automatically, so the user does not have to take care of that.
  • file_cre_attr: file creation and attributs flags. Each bit corresponds to the appropriate file attribut:
    Bit Mask Description
    0 0x01 Read Only
    1 0x02 Hidden
    2 0x04 System
    3 0x08 Volume Label
    4 0x10 Subdirectory
    5 0x20 Archive
    6 0x40 Device (internal use only, never found on disk)
    7 0x80 File creation flag. If file does not exist and this flag is set, a new file with specified name will be created.
      Note : Long File Names (LFN) are not supported.
Requires MMC/SD card and MMC library must be initialized for file operations.
Example
// create file with archive attribute if it does not already exist
Mmc_Fat_Assign("MIKRO007.TXT",0xA0);

Mmc_Fat_Reset

Prototype void Mmc_Fat_Reset(unsigned long *size);
Returns Nothing.
Description Procedure resets the file pointer (moves it to the start of the file) of the assigned file, so that the file can be read.
Parameters:

  • size: buffer to store file size to. After file has been open for reading, its size is returned through this parameter.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
unsigned long size;
...
Mmc_Fat_Reset(&size);

 

Mmc_Fat_Read

Prototype void Mmc_Fat_Read(unsigned short *bdata);
Returns Nothing.
Description Reads a byte from the currently assigned file opened for reading. Upon function execution, file pointers will be set to the next character in the file.
Parameters:

  • bdata: buffer to store read byte to. Upon this function execution read byte is returned through this parameter.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
The file must be opened for reading.
Example
char character;
...
Mmc_Fat_Read(&character);

Mmc_Fat_Rewrite

Prototype void Mmc_Fat_Rewrite();
Returns Nothing.
Description Opens the currently assigned file for writing. If the file is not empty its content will be erased.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// open file for writing
Mmc_Fat_Rewrite();

Mmc_Fat_Append

Prototype void Mmc_Fat_Append();
Returns Nothing.
Description Opens the currently assigned file for appending. Upon this function execution file pointers will be positioned after the last byte in the file, so any subsequent file write operation will start from there.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// open file for appending
Mmc_Fat_Append();

Mmc_Fat_Delete

Prototype char Mmc_Fat_Delete();
Returns
  • 1 – if there are no assigned files
  • 2 – if an error occured during deleting
  • 0 – if deleting was successful
Description Deletes currently assigned file from MMC/SD card.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// delete current file
if (Mmc_Fat_Delete() == 0)
...


Mmc_Fat_Write

Prototype void Mmc_Fat_Write(char *fdata, unsigned data_len);
Returns Nothing.
Description Writes requested number of bytes to the currently assigned file opened for writing.
Parameters:

  • fdata: data to be written.
  • data_len: number of bytes to be written.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
The file must be opened for writing.
Example
Mmc_Fat_Write(txt,255);
Mmc_Fat_Write("Hello world",255);

Mmc_Fat_Set_File_Date

Prototype void Mmc_Fat_Set_File_Date(unsigned int year, unsigned short month, unsigned short day, unsigned short hours, unsigned short mins, unsigned short seconds);
Returns Nothing.
Description Sets the date/time stamp. Any subsequent file write operation will write this stamp to the currently assigned file’s time/date attributs.
Parameters:

  • year: year attribute. Valid values: 1980-2107
  • month: month attribute. Valid values: 1-12
  • day: day attribute. Valid values: 1-31
  • hours: hours attribute. Valid values: 0-23
  • mins: minutes attribute. Valid values: 0-59
  • seconds: seconds attribute. Valid values: 0-59
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
The file must be opened for writing.
Example
// April 1st 2005, 18:07:00
Mmc_Fat_Set_File_Date(2005, 4, 1, 18, 7, 0);

Mmc_Fat_Get_File_Date

Prototype void Mmc_Fat_Get_File_Date(unsigned int *year, unsigned short *month, unsigned short *day, unsigned short *hours, unsigned short *mins);
Returns Nothing.
Description Reads time/date attributes of the currently assigned file.
Parameters:

  • year: buffer to store year attribute to. Upon function execution year attribute is returned through this parameter.
  • month: buffer to store month attribute to. Upon function execution month attribute is returned through this parameter.
  • day: buffer to store day attribute to. Upon function execution day attribute is returned through this parameter.
  • hours: buffer to store hours attribute to. Upon function execution hours attribute is returned through this parameter.
  • mins: buffer to store minutes attribute to. Upon function execution minutes attribute is returned through this parameter.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// get Date/time of file
unsigned yr;
char mnth, dat, hrs, mins;
...
file_Name = "MYFILEABTXT";
Mmc_Fat_Assign(file_Name);
Mmc_Fat_Get_File_Date(&yr, &mnth, &day, &hrs, &mins);

Mmc_Fat_Get_File_Date_Modified

Prototype void Mmc_Fat_Get_File_Date_Modified(unsigned int *year, unsigned short *month, unsigned short *day, unsigned short *hours, unsigned short *mins);
Returns Nothing.
Description Retrieves the last modification date/time for the currently selected file.
Parameters:

  • year: buffer to store year of modification attribute to. Upon function execution year of modification attribute is returned through this parameter.
  • month: buffer to store month of modification attribute to. Upon function execution month of modification attribute is returned through this parameter.
  • day: buffer to store day of modification attribute to. Upon function execution day of modification attribute is returned through this parameter.
  • hours: buffer to store hours of modification attribute to. Upon function execution hours of modification attribute is returned through this parameter.
  • mins: buffer to store minutes of modification attribute to. Upon function execution minutes of modification attribute is returned through this parameter.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// get modification Date/time of file
unsigned yr;
char mnth, dat, hrs, mins;
...
file_Name = "MYFILEABTXT";
Mmc_Fat_Assign(file_Name);
Mmc_Fat_Get_File_Date_Modified(&yr, &mnth, &day, &hrs, &mins);

Mmc_Fat_Get_File_Size

Prototype unsigned long Mmc_Fat_Get_File_Size();
Returns This function returns size of active file (in bytes).
Description This function reads size of the currently assigned file in bytes.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
// get Date/time of file
unsigned yr;
char mnth, dat, hrs, mins;
...
file_name = "MYFILEXXTXT";
Mmc_Fat_Assign(file_name);
mmc_size = Mmc_Fat_Get_File_Size;

Mmc_Get_File_Write_Sector

Prototype unsigned long Mmc_Get_File_Write_Sector();
Description This function returns the current file write sector.
Parameters None.
Returns This function returns the current file write sector.
Requires MMC/SD card and MMC library must be initialized for file operations.
The file must be previously assigned.
Example
unsigned long sector;
...
sector = Mmc_Get_File_Write_Sector();
Notes None.

Connect Memory Card using PIC18F4520 Code schematichMmc_Fat_Get_Swap_File

Prototype unsigned long Mmc_Fat_Get_Swap_File(unsigned long sectors_cnt, char* filename, char file_attr);
Returns
  • Number of the start sector for the newly created swap file, if there was enough free space on the MMC/SD card to create file of required size.
  • 0 – otherwise.
Description This function is used to create a swap file of predefined name and size on the MMC/SD media. If a file with specified name already exists on the media, search for consecutive sectors will ignore sectors occupied by this file. Therefore, it is recommended to erase such file if it already exists before calling this function. If it is not erased and there is still enough space for a new swap file, this function will delete it after allocating new memory space for a new swap file.
The purpose of the swap file is to make reading and writing to MMC/SD media as fast as possible, by using the Mmc_Read_Sector() and Mmc_Write_Sector() functions directly, without potentially damaging the FAT system. The swap file can be considered as a “window” on the media where the user can freely write/read data. Its main purpose in the library is to be used for fast data acquisition; when the time-critical acquisition has finished, the data can be re-written into a “normal” file, and formatted in the most suitable way.
Parameters:

  • sectors_cnt: number of consecutive sectors that user wants the swap file to have.
  • filename: name of the file that should be assigned for file operations. File name should be in DOS 8.3 (file_name.extension) format. The file name and extension will be automatically padded with spaces by the library if they have less than length required (i.e. “mikro.tx” -> “mikro .tx “), so the user does not have to take care of that. The file name and extension are case insensitive. The library will convert them to proper case automatically, so the user does not have to take care of that. Also, in order to keep backward compatibility with the first version of this library, file names can be entered as UPPERCASE string of 11 bytes in length with no dot character between file name and extension (i.e. “MIKROELETXT” -> MIKROELE.TXT). In this case the last 3 characters of the string are considered to be file extension.
  • file_attr: file creation and attributs flags. Each bit corresponds to the appropriate file attribut:
    Bit Mask Description
    0 0x01 Read Only
    1 0x02 Hidden
    2 0x04 System
    3 0x08 Volume Label
    4 0x10 Subdirectory
    5 0x20 Archive
    6 0x40 Device (internal use only, never found on disk)
    7 0x80 Not used
      Note : Long File Names (LFN) are not supported.
Requires MMC/SD card and MMC library must be initialized for file operations.
Example
//-------------- Tries to create a swap file, whose size will be at least 100 sectors.
//If it succeeds, it sends the No. of start sector over UART
void M_Create_Swap_File(){
  size = Mmc_Fat_Get_Swap_File(100);
  if (size <> 0) {
    UART1_Write(0xAA);
    UART1_Write(Lo(size));
    UART1_Write(Hi(size));
    UART1_Write(Higher(size));
    UART1_Write(Highest(size));
    UART1_Write(0xAA);
  } 
}

 

 

For more detail: Connect Memory Card using PIC18F4520 Code




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  • microcontroller easy projects on proteus
  • audio recording using pic microcontroller with external memory
  • memory card parameter code
  • memorycard project pdf

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