Difference between revisions of "Component: FAT (SD, SDHC) (Storage)"
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− | A basic schematic showing how to interface a 3V3 Microcontroller to a SD card. | + | A basic schematic showing how to interface a 3V3 Microcontroller to a SD card. The pull up resistor on the CS pin is not strictly necessary but ensures that the card is disabled when the Microcontroller is powering up or in reset. |
[[File:sd-3V3.jpg]] | [[File:sd-3V3.jpg]] | ||
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===Interfacing a 5V Microcontroller=== | ===Interfacing a 5V Microcontroller=== |
Revision as of 10:12, 11 June 2014
Author | Matrix Ltd. |
Version | 1.10 |
Category | Storage |
Contents
- 1 FAT (SD, SDHC) component
- 2 Connections
- 3 Examples
- 4 Downloadable macro reference
- 4.1 ReadStringFromFile
- 4.2 WriteByteToBuffer
- 4.3 MoveToNextFileSector
- 4.4 ReadFileSector
- 4.5 ReadByteFromFile
- 4.6 DeleteFile
- 4.7 CreateFile
- 4.8 ScanCurrentFolder
- 4.9 ReadByteFromScan
- 4.10 OpenFolder
- 4.11 ReadByteFromBuffer
- 4.12 ReadFileLength
- 4.13 OpenFile
- 4.14 WriteFileSector
- 4.15 SetFileIndex
- 4.16 AppendStringToFile
- 4.17 Initialise
- 5 Simulation macro reference
- 6 Property reference
FAT (SD, SDHC) component
FAT component allowing access to read and write files on a SD, SDHC or MMC card.
The component automatically detects the filesystem on the card on initialise so FAT16 and FAT32 are fully supported.
Connections
SD Card and micro SD Card Pinout
Interfacing a 3V3 Microcontroller
A basic schematic showing how to interface a 3V3 Microcontroller to a SD card. The pull up resistor on the CS pin is not strictly necessary but ensures that the card is disabled when the Microcontroller is powering up or in reset.
Interfacing a 5V Microcontroller
A basic schematic showing how to interface a 5V Microcontroller to a SD card. The 3V3 supply is created using a potential divider to take the 5V supply down to 3V3. Potential dividers are also present on the microcontroller output pins MOSI, SCK and CS. The MISO signal is an output from the SD card so no potential divider is needed, a 5V microcontroller should be able to read the 3V3 signal as a logic high. Take care not to output a high signal to the MISO pin or you risk damaging the SD card.
Examples
Reading data from a text file
Example to read a text file from a SD card or from a text file in simulation and display on a 16 x 2 character LCD. The text file needs to be in the same directory as the Flowcode .fcfx project file for the simulation to run correctly.
Console showing current 512 byte sector data
Console showing high level FAT status
Parsing a standard .BMP image file
Example to read a bitmap image file from a SD card or from a bitmap file in simulation and display on a graphical LCD. The bitmapfile needs to be in the same directory as the Flowcode .fcfx project file for the simulation to run correctly.
Demo bitmap files referenced in the example.
Picture showing a bitmap being displayed on a GLCD component.
Data logger Simple
Example showing how to take a collection of analogue readings and save them into a text based file, the simple way.
FAT data logger simple but slow
Data logger Advanced
Example showing how to take a collection of analogue readings and save them into a text based file, the fast way.
Downloadable macro reference
ReadStringFromFile
Reads a string from the currently open file. Auto increments the position in the file.
An empty string signifies the end of the file has been reached.
Parameters
- BYTE NumBytes
- Maximum number of bytes to attempt to read
- BYTE EndChar
- Ends the string if the value specified is found, default is 0
Return value
WriteByteToBuffer
Writes a single byte to the current 512 byte local sector buffer.
Parameters
- UINT Address
- Address Range 0 - 511
- BYTE Data
- Data Byte to write to the buffer
Return value
- This call does not return a value
MoveToNextFileSector
Attempts to move to the next sector in the file.
When reading a file you would leave force next sector set to 0.
When writing a file you would leave force next sector set to 1 to allow new sectors to be created as the file grows.
Returns 0 for success
Parameters
- BYTE Force_Next_Sector
- 0 = Don't add new sector, 1 = Add new sector if we are at the end of the file
Return value
ReadFileSector
Overwrites local buffer with the current file sector from the disk.
Used to restore the local sector buffer with the actual sector stored on the card.
Return = 0 : Local buffer refreshed with current card sector
Return > 0 : Error
Parameters
- This macro has no parameters
Return value
ReadByteFromFile
Reads a byte from the currently open file. Auto increments the position in the file.
A return value of 0 may signify the end of the file has been reached (depending on the contents of the file).
Parameters
- This macro has no parameters
Return value
DeleteFile
Searches for and deletes a file in the current folder location on the card. Default = Root
Returns 0 for success.
Parameters
- <- STRING Filename
- 8.3 format filename e.g."file.txt"
- This parameter may be returned back to the caller
Return value
CreateFile
Creates a file in the current folder location on the card. Default = Root
Returns 0 for success
File must be opened using "Open_File" after creation before writing any data.
Parameters
- <- STRING Filename
- 8.3 format filename e.g."file.txt"
- This parameter may be returned back to the caller
Return value
ScanCurrentFolder
Method for retreiving file or folder names for the card to allow for dynamic file opening or playback. Does not currently simulate.
0 - Filetype found and stored into string array, 1 - End of folder reached, 2 - Filetype mismatch 3 - Empty
Parameters
- UINT Current_Idx
- Contains the current pointer in the directory table. Values from 0 to 511 to completley search the current folder for a files or folders
- BYTE Scan_Type
- Sets the scan to search for Files or Folders. 0 = Scan for files, 1 = Scan for folders
Return value
ReadByteFromScan
Returns a byte of the name of the file or folder retreived from the Scan_Current_folder function.
Return = ASCII byte at position Idx from the folder name or file name at position Current_Idx in the directory
Parameters
- BYTE idx
- 0 - 11 for a file, 0 - 7 for a folder
Return value
OpenFolder
".." - Jumps up a directory, if at root then remains in root
"root" - Jumps directly back to the root directory
"foldername" - Opens folder named foldername
Parameters
- <- STRING Folder_Name
- This parameter may be returned back to the caller
Return value
ReadByteFromBuffer
Reads a byte of data from the local sector buffer.
Return = Data byte read from the local sector buffer.
Parameters
- UINT Address
- 0 - 511 - Contains the position of the byte to be read
Return value
ReadFileLength
Returns the number of bytes in the current sector that are used by the current open file.
Return = 512 - Sector is filled with file data
Return < 512 - Last sector of the file, Retval specifies how many bytes of data are remaining in the sector
Parameters
- This macro has no parameters
Return value
OpenFile
Searches for and opens a file for reading or writing from within the current directory on the disk.
Returns 0 for success.
Parameters
- <- STRING Filename
- 8.3 filename of the file we are trying to open e.g. "file.txt"
- This parameter may be returned back to the caller
Return value
WriteFileSector
Overwrites the current sector on the memory card with the contents of the local sector buffer. See write_byte_to_buffer function.
Return = 0 - File sector written successfully.
Return > 0 - File sector write error
Parameters
- This macro has no parameters
Return value
SetFileIndex
Sets the current file index and used to switch between several open file streams.
Default = 0.
Parameters
- BYTE File_Index
- File index ranges from 0 to (Max Concurrent Files - 1)
Return value
- This call does not return a value
AppendStringToFile
Adds the contents of the data string parameter to the end of the currently open file.
Returns 0 for success.
Parameters
- <- STRING Data_String
- Data to append to the end of the file
- This parameter may be returned back to the caller
Return value
Initialise
Attempts to communicate with the SD card and if successful sets up the file system.
Returns 0 for success.
Parameters
- This macro has no parameters
Return value
Simulation macro reference
This component does not contain any simulation macros
Property reference
Max Concurrent Files
This property is of type Signed integer and can be referenced with the variable name max_concurrent_files.
Specifies how many concurrent files can be opened at any one time.
Use the SetFileIndex macro to switch between concurrent files.
Channel
This property is of type Fixed list of ints and can be referenced with the variable name Channel.
SPI communications channel
Prescaler
This property is of type Fixed list of ints and can be referenced with the variable name PR_SCALE.
SPI initial clock divider - Frequency should be under 400khz to allow startup to work
Chip Select - CS
This property is of type Single digital pin and can be referenced with the variable name cs_pin.
Chip Select Pin for SPI
Data In - MISO / SDI
This property is of type Single digital pin and can be referenced with the variable name miso_pin.
Data In SPI Pin
Data Out - MOSI / SDO
This property is of type Single digital pin and can be referenced with the variable name mosi_pin.
Data Out SPI Pin
Serial Clock - SCK
This property is of type Single digital pin and can be referenced with the variable name sck_pin.
Master Clock SPI pin
Root Directory
This property is of type Directory and can be referenced with the variable name root_dir.
Directory flagged as root for simulation.
Modern windows systems do not like you writing files to a hard drive root directory so a directory off the root is advised.
Auto Insert Card
This property is of type True or false and can be referenced with the variable name AutoInsertCard.
When set to yes the SD card will be automatically inserted at the start of simulation,
Otherwise you must manually click the card on the panel to insert.