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.

- 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 writing operation, make sure not to 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 great assistance.
Library Dependency Tree

External dependencies of Compact Flash Library
The following variables must be defined in all projects using Compact Flash Library: | Description : | Example : |
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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
- Cf_Init
- Cf_Detect
- Cf_Enable
- Cf_Disable
- Cf_Read_Init
- Cf_Read_Byte
- Cf_Write_Init
- Cf_Write_Byte
- Cf_Read_Sector
- Cf_Write_Sector
Routines for file handling:
- Cf_Fat_Init
- Cf_Fat_QuickFormat
- Cf_Fat_Assign
- Cf_Fat_Reset
- Cf_Fat_Read
- Cf_Fat_Rewrite
- Cf_Fat_Append
- Cf_Fat_Delete
- Cf_Fat_Write
- Cf_Fat_Set_File_Date
- Cf_Fat_Get_File_Date
- Cf_Fat_Get_File_Date_Modified
- Cf_Fat_Get_File_Size
- Cf_Fat_Get_Swap_File
The following routine is for the internal use by compiler only:
- Cf_Issue_ID_Command
Cf_Init
Prototype |
void Cf_Init(); |
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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(); |
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Description |
Checks for presence of CF card by reading the |
Parameters |
None. |
Returns |
|
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 |
|
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 |
|
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 |
|
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 |
Parameters |
|
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 |
Parameters |
|
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 |
|
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 |
|
Returns |
|
Requires |
Nothing. |
Example |
// format and initialize the FAT library - if (!Cf_Fat_QuickFormat(&cf_fat_label)) { ... } |
Notes |
|
Cf_Fat_Assign
Prototype |
unsigned int Cf_Fat_Assign(char *filename, char file_cre_attr); |
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Description |
Assigns file for file operations (read, write, delete...). All subsequent file operations will be applied over the assigned file. |
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Parameters |
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Returns |
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Requires |
CF card and CF library must be initialized for file operations. See Cf_Fat_Init. |
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Example |
// create file with archive attributes if it does not already exist Cf_Fat_Assign("MIKRO007.TXT",0xA0); |
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Notes | Long File Names (LFN) are not supported. |
Cf_Fat_Reset
Prototype |
void Cf_Fat_Reset(unsigned long *size); |
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Description |
Opens currently assigned file for reading. |
Parameters |
|
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 |
|
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(); |
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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(); |
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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); |
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Description |
Writes requested number of bytes to currently assigned file opened for writing. |
Parameters |
|
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); |
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Description |
Sets the date/time stamp. Any subsequent file writing operation will write this stamp to currently assigned file's time/date attributes. |
Parameters |
|
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); |
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Description |
Reads time/date attributes of currently assigned file. |
Parameters |
|
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); |
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Description |
Retrieves the last modification date/time of the currently assigned file. |
Parameters |
|
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); |
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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. |
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Parameters |
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Returns |
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Requires |
CF card and CF library must be initialized for file operations. See Cf_Fat_Init. |
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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); } |
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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.
// 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
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