Compact Flash Library

The Compact Flash Library provides routines for accessing data on Compact Flash card (abbr. CF further in text). CF cards are widely used memory elements, commonly used with digital cameras. Great capacity and excellent access time of only a few microseconds make them very attractive for microcontroller applications.

In CF card, data is divided into sectors. One sector usually comprises 512 bytes. Routines for file handling, the Cf_Fat routines, are not performed directly but successively through 512B buffer.

  Important :

Library Dependency Tree

Compact Flash Library Dependency Tree

External dependencies of Compact Flash Library

The following variables must be defined in all projects using Compact Flash Library: Description : Example :
extern sfr unsigned int CF_Data_Port; Compact Flash Data Port. char CF_Data_Port at PORTF;
extern sfr sbit CF_RDY; Ready signal line. sbit CF_RDY at RD7_bit;
extern sfr sbit CF_WE; Write Enable signal line. sbit CF_WE at RD6_bit;
extern sfr sbit CF_OE; Output Enable signal line. sbit CF_OE at RD5_bit;
extern sfr sbit CF_CD1; Chip Detect signal line. sbit CF_CD1 at RD4_bit;
extern sfr sbit CF_CE1; Chip Enable signal line. sbit CF_CE1 at RD3_bit;
extern sfr sbit CF_A2; Address pin 2. sbit CF_A2 at RD2_bit;
extern sfr sbit CF_A1; Address pin 1. sbit CF_A1 at RD1_bit;
extern sfr sbit CF_A0; Address pin 0. sbit CF_A0 at RD0_bit;
extern sfr sbit CF_RDY_direction; Direction of the Ready pin. sbit CF_RDY_direction at TRISD7_bit;
extern sfr sbit CF_WE_direction; Direction of the Write Enable pin. sbit CF_WE_direction at TRISDB6_bit;
extern sfr sbit CF_OE_direction; Direction of the Output Enable pin. sbit CF_OE_direction at TRISD5_bit;
extern sfr sbit CF_CD1_direction; Direction of the Chip Detect pin. sbit CF_CD1_direction at TRISD4_bit;
extern sfr sbit CF_CE1_direction; Direction of the Chip Enable pin. sbit CF_CE1_direction at TRISD3_bit;
extern sfr sbit CF_A2_direction; Direction of the Address 2 pin. sbit CF_A2_direction at TRISD2_bit;
extern sfr sbit CF_A1_direction; Direction of the Address 1 pin. sbit CF_A1_direction at TRISD1_bit;
extern sfr sbit CF_A0_direction; Direction of the Address 0 pin. sbit CF_A0_direction at TRISD0_bit;

Library Routines

Routines for file handling:

The following routine is for the internal use by compiler only:

Cf_Init

Prototype

void Cf_Init();

Description

Initializes ports appropriately for communication with CF card.

Parameters

None.

Returns

Nothing.

Requires

External dependencies of the library from the top of the page must be defined before using this function.

Example
// set compact flash pinout 
char Cf_Data_Port at PORTF;

sbit CF_RDY at RD7_bit;
sbit CF_WE  at RD6_bit;
sbit CF_OE  at RD5_bit;
sbit CF_CD1 at RD4_bit;
sbit CF_CE1 at RD3_bit;
sbit CF_A2  at RD2_bit;
sbit CF_A1  at RD1_bit;
sbit CF_A0  at RD0_bit;

sbit CF_RDY_direction at TRISD7_bit;
sbit CF_WE_direction  at TRISD6_bit;
sbit CF_OE_direction  at TRISD5_bit;
sbit CF_CD1_direction at TRISD4_bit;
sbit CF_CE1_direction at TRISD3_bit;
sbit CF_A2_direction  at TRISD2_bit;
sbit CF_A1_direction  at TRISD1_bit;
sbit CF_A0_direction  at TRISD0_bit;
// end of compact flash pinout
...
Cf_Init();      // initialize CF 
Notes

None.

Cf_Detect

Prototype

unsigned int Cf_Detect();

Description

Checks for presence of CF card by reading the chip detect pin.

Parameters

None.

Returns

  • 1 - if CF card was detected
  • 0 - otherwise

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// Wait until CF card is inserted:
do
  asm nop;
while (!Cf_Detect());
Notes

dsPIC30 family MCU and CF card voltage levels are different. The user must ensure that MCU's pin connected to CD line can read CF card Logical One correctly.

Cf_Enable

Prototype

void Cf_Enable();

Description

Enables the device. Routine needs to be called only if you have disabled the device by means of the Cf_Disable routine. These two routines in conjunction allow you to free/occupy data line when working with multiple devices.

Parameters

None.

Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// enable compact flash
Cf_Enable();
Notes

None.

Cf_Disable

Prototype

void Cf_Disable();

Description

Routine disables the device and frees the data lines for other devices. To enable the device again, call Cf_Enable. These two routines in conjunction allow you to free/occupy data line when working with multiple devices.

Parameters

None.

Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// disable compact flash
Cf_Disable();
Notes

None.

Cf_Read_Init

Prototype

void Cf_Read_Init(unsigned long address, unsigned short sector_count);

Description

Initializes CF card for reading.

Parameters
  • address: the first sector to be prepared for reading operation.
  • sector_count: number of sectors to be prepared for reading operation.
Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// initialize compact flash for reading from sector 590
Cf_Read_Init(590, 1);
Notes

None.

Cf_Read_Byte

Prototype

unsigned char Cf_Read_Byte();

Description

Reads one byte from Compact Flash sector buffer location currently pointed to by internal read pointers. These pointers will be autoicremented upon reading.

Parameters

None.

Returns

Returns a byte read from Compact Flash sector buffer.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

CF card must be initialized for reading operation. See Cf_Read_Init.

Example
// Read a byte from compact flash:
unsigned char data_;
...
data_ = Cf_Read_Byte();
Notes Higher byte of the unsigned return value is cleared.

Cf_Write_Init

Prototype

void Cf_Write_Init(unsigned long address, unsigned short sectcnt);

Description

Initializes CF card for writing.

Parameters
  • address: the first sector to be prepared for writing operation.
  • sectcnt: number of sectors to be prepared for writing operation.
Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// initialize compact flash for writing to sector 590
Cf_Write_Init(590, 1);
Notes

None.

Cf_Write_Byte

Prototype

void Cf_Write_Byte(unsigned short data_);

Description

Writes a byte to Compact Flash sector buffer location currently pointed to by writing pointers. These pointers will be autoicremented upon reading. When sector buffer is full, its contents will be transfered to appropriate flash memory sector.

Parameters
  • data_: byte to be written.
Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

CF card must be initialized for writing operation. See Cf_Write_Init.

Example
char data_ = 0xAA;
...
Cf_Write_Byte(data_);
Notes

None.

Cf_Read_Sector

Prototype

void Cf_Read_Sector(unsigned long sector_number, unsigned short *buffer);

Description

Reads one sector (512 bytes). Read data is stored into buffer provided by the buffer parameter.

Parameters
  • sector_number: sector to be read.
  • buffer: data buffer of at least 512 bytes in length.
Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// read sector 22
unsigned short data[512];
...
Cf_Read_Sector(22, data);
Notes

None.

Cf_Write_Sector

Prototype

void Cf_Write_Sector(unsigned long sector_number, unsigned short *buffer);

Description

Writes 512 bytes of data provided by the buffer parameter to one CF sector.

Parameters
  • sector_number: sector to be written to.
  • buffer: data buffer of 512 bytes in length.
Returns

Nothing.

Requires

The corresponding MCU ports must be appropriately initialized for CF card. See Cf_Init.

Example
// write to sector 22
unsigned short data[512];
...
Cf_Write_Sector(22, data);
Notes

None.

Cf_Fat_Init

Prototype

unsigned int Cf_Fat_Init();

Description

Initializes CF card, reads CF FAT16 boot sector and extracts necessary data needed by the library.

Parameters

None.

Returns

  • 0 - if CF card was detected and successfully initialized
  • 1 - if FAT16 boot sector was not found
  • 255 - if card was not detected

Requires

Nothing.

Example
// Init the FAT library
if (!Cf_Fat_Init()) {    // Init the FAT library
...
}
Notes

None.

Cf_Fat_QuickFormat

Prototype

unsigned int Cf_Fat_QuickFormat(char *cf_fat_label);

Description

Formats to FAT16 and initializes CF card.

Parameters
  • cf_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, the volume will not be labeled.
Returns

  • 0 - if CF card was detected, successfully formated and initialized
  • 1 - if FAT16 format was unsuccessful
  • 255 - if card was not detected

Requires

Nothing.

Example
//  format and initialize the FAT library - 
if (!Cf_Fat_QuickFormat(&cf_fat_label)) {
...
}
Notes
  • This routine can be used instead or in conjunction with Cf_Fat_Init routine.
  • If CF 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.

Cf_Fat_Assign

Prototype

unsigned int Cf_Fat_Assign(char *filename, char file_cre_attr);

Description

Assigns file for file operations (read, write, delete...). All subsequent file operations will be applied over the assigned file.

Parameters
  • filename: name of the file that should be assigned for file operations. The 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 the 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_cre_attr: file creation and attributes flags. Each bit corresponds to the appropriate file attribute:
  • 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 the file does not exist and this flag is set, a new file with specified name will be created.
Returns

  • 0 if file does not exist and no new file is created.
  • 1 if file already exists or file does not exist but a new file is created.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

Example
// create file with archive attributes if it does not already exist
Cf_Fat_Assign("MIKRO007.TXT",0xA0);
Notes Long File Names (LFN) are not supported.

Cf_Fat_Reset

Prototype

void Cf_Fat_Reset(unsigned long *size);

Description

Opens currently assigned file for reading.

Parameters
  • size: buffer to store file size to. After file has been open for reading its size is returned through this parameter.
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
unsigned long size;
...
Cf_Fat_Reset(size);
Notes

None.

Cf_Fat_Read

Prototype

void Cf_Fat_Read(unsigned short *bdata);

Description

Reads a byte from 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.
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

File must be open for reading. See Cf_Fat_Reset.

Example
char character;
...
Cf_Fat_Read(&character);
Notes

None.

Cf_Fat_Rewrite

Prototype

void Cf_Fat_Rewrite();

Description

Opens currently assigned file for writing. If the file is not empty its content will be erased.

Parameters

None.

Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

The file must be previously assigned. See Cf_Fat_Assign.

Example
// open file for writing
Cf_Fat_Rewrite();
Notes

None.

Cf_Fat_Append

Prototype

void Cf_Fat_Append();

Description

Opens 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 writing operation will start from there.

Parameters

None.

Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
// open file for appending
Cf_Fat_Append();
Notes

None.

Cf_Fat_Delete

Prototype

void Cf_Fat_Delete();

Description

Deletes currently assigned file from CF card.

Parameters

None.

Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
// delete current file
Cf_Fat_Delete();
Notes

None.

Cf_Fat_Write

Prototype

void Cf_Fat_Write(char *fdata, unsigned data_len);

Description

Writes requested number of bytes to currently assigned file opened for writing.

Parameters
  • fdata: data to be written.
  • data_len: number of bytes to be written.
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

File must be open for writing. See Cf_Fat_Rewrite or Cf_Fat_Append.

Example
char file_contents[42];
...
Cf_Fat_Write(file_contents, 42); // write data to the assigned file
Notes

None.

Cf_Fat_Set_File_Date

Prototype

void Cf_Fat_Set_File_Date(unsigned int year, unsigned short month, unsigned short day, unsigned short hours, unsigned short mins, unsigned short seconds);

Description

Sets the date/time stamp. Any subsequent file writing operation will write this stamp to currently assigned file's time/date attributes.

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
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

File must be open for writing. See Cf_Fat_Rewrite or Cf_Fat_Append.

Example
Cf_Fat_Set_File_Date(2005,9,30,17,41,0);
Notes

None.

Cf_Fat_Get_File_Date

Prototype

void Cf_Fat_Get_File_Date(unsigned int *year, unsigned short *month, unsigned short *day, unsigned short *hours, unsigned short *mins);

Description

Reads time/date attributes of 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.
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
unsigned year;
char month, day, hours, mins;
...
Cf_Fat_Get_File_Date(&year, &month, &day, &hours, &mins);
Notes

None.

Cf_Fat_Get_File_Date_Modified

Prototype

void Cf_Fat_Get_File_Date_Modified(unsigned int *year, unsigned short *month, unsigned short *day, unsigned short *hours, unsigned short *mins);

Description

Retrieves the last modification date/time of the currently assigned 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.
Returns

Nothing.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
unsigned year;
char month, day, hours, mins;
...
Cf_Fat_Get_File_Date_Modified(&year, &month, &day, &hours, &mins);
Notes

None.

Cf_Fat_Get_File_Size

Prototype

unsigned long Cf_Fat_Get_File_Size();

Description

This function reads size of currently assigned file in bytes.

Parameters

None.

Returns

Size of the currently assigned file in bytes.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

File must be previously assigned. See Cf_Fat_Assign.

Example
unsigned long my_file_size;
...
my_file_size = Cf_Fat_Get_File_Size();
Notes

None.

Cf_Fat_Get_Swap_File

Prototype

unsigned long Cf_Fat_Get_Swap_File(unsigned long sectors_cnt, char *filename, char file_attr);

Description

This function is used to create a swap file of predefined name and size on the CF 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 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 CF media as fast as possible, by using the Cf_Read_Sector() and Cf_Write_Sector() functions directly, without potentially damaging the FAT system. Swap file can be considered as a "window" on the media where the user can freely write/read data. It's main purpose in the this 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. The 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 the 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 attributes flags. Each bit corresponds to the appropriate file attribute:
  • 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

Returns

  • Number of the start sector for the newly created swap file, if there was enough free space on CF card to create file of required size.
  • 0 - otherwise.

Requires

CF card and CF library must be initialized for file operations. See Cf_Fat_Init.

Example
//-------------- Try to create a swap file with archive atribute, whose size will be at least 1000 sectors.
//               If it succeeds, it sends the No. of start sector over UART
unsigned long size;
...
size = Cf_Fat_Get_Swap_File(1000, "mikroE.txt", 0x20);
if (size) {
  UART1_Write(0xAA);
  UART1_Write(Lo(size));
  UART1_Write(Hi(size));
  UART1_Write(Higher(size));
  UART1_Write(Highest(size));
  UART1_Write(0xAA);
}
Notes Long File Names (LFN) are not supported.

Library Example

The following example writes 512 bytes at sector no.620, and then reads the data and sends it over UART1 for a visual check. Hardware configurations in this example are made for the dsPICPRO2 board and dsPIC30F6014A.

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// set compact flash pinout
char Cf_Data_Port at PORTF;

sbit CF_RDY at RD7_bit;
sbit CF_WE  at RD6_bit;
sbit CF_OE  at RD5_bit;
sbit CF_CD1 at RD4_bit;
sbit CF_CE1 at RD3_bit;
sbit CF_A2  at RD2_bit;
sbit CF_A1  at RD1_bit;
sbit CF_A0  at RD0_bit;

sbit CF_RDY_direction at TRISD7_bit;
sbit CF_WE_direction  at TRISD6_bit;
sbit CF_OE_direction  at TRISD5_bit;
sbit CF_CD1_direction at TRISD4_bit;
sbit CF_CE1_direction at TRISD3_bit;
sbit CF_A2_direction  at TRISD2_bit;
sbit CF_A1_direction  at TRISD1_bit;
sbit CF_A0_direction  at TRISD0_bit;
// end of cf pinout

char SignalPort           at PORTB;
char SignalPort_direction at TRISB;

void InitCF() {
  CF_CD1_direction = 1;
  while (Cf_Detect() == 0)                // wait until CF card is inserted
    ;
  Cf_Init();                              // initialize CF
  while (!CF_RDY)
    ;
  Delay_ms(2000);                         // wait for a while until the card is stabilized
}                                         //   period depends on used CF card

void TestBytes() {
  unsigned int i;

  ///// Write numbers 0..511 to sector 590
  Cf_Write_Init(590,1);                   // Initialize write at sector address 590
                                          //     for 1 sector
  SignalPort = 0x03;                      // Notify that write has started
  Delay_ms(1000);
  for (i=0; i<=511; i++)                  // Write 512 bytes to sector 590
    Cf_Write_Byte(i);

  SignalPort = 0x07;                      // Notify that write end and read start
  Delay_ms(1000);

  Cf_Read_Init(590,1);                    // Initialize read from sector address 590
                                          //    for 1 sector
  for (i=0; i<=511; i++) {                // Read 512 bytes from sector address 590
    SignalPort = Cf_Read_Byte();          // Read one byte at time and display
                                          //    readings on signal port
    Delay_ms(5);                          // Wait for a while to see results
  }
  Delay_ms(1000);

  ///// Write numbers 511..0 to sector 590
  Cf_Write_Init(590,1);                   // Initialize write at sector address 590
                                          //     for 1 sector
  SignalPort = 0x03;                      // Notify that write has started
  Delay_ms(1000);
  for (i=0; i<=511; i++)                  // Write 512 bytes to sector 590
    Cf_Write_Byte(511-i);

  SignalPort = 0x07;                      // Notify that write end and read start
  Delay_ms(1000);

  Cf_Read_Init(590,1);                    // Initialize read from sector address 590
                                          //    for 1 sector
  for (i=0; i<=511; i++) {                // Read 512 bytes from sector address 590
    SignalPort = Cf_Read_Byte();          // Read one byte at time and display
                                          //    readings on signal port
    Delay_ms(5);                          // Wait for a while to see results
  }
  Delay_ms(1000);
}

// Main program
void main() {

  ADPCFG = 0xFFFF;                        // disable A/D inputs

  SignalPort_direction = 0;               // designate PORTC as output
  SignalPort = 0x01;                      // Notify test start
  InitCF();

  TestBytes();
  SignalPort = 0x0F;                      // Notify test end
}

HW Connection

Pin diagram of CF memory card

Pin diagram of CF memory card

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