User manual

402
mikoBasic PRO for dsPIC30/33 and PIC24
MikroElektronika
Prototype
sub function Mmc_Fat_Get_Swap_File(dim sectors_cnt as longword, dim byref
lename as string[11], dim le_attr as byte) as longword
Description This function is used to create a swap le of predened name and size on the MMC/SD media. If a
le with specied name already exists on the media, search for consecutive sectors will ignore sectors
occupied by this le. Therefore, it is recommended to erase such le if it already exists before calling
this function. If it is not erased and there is still enough space for a new swap le, this function will
delete it after allocating new memory space for a new swap le.
The purpose of the swap le 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 le can be considered as a “window” on the media where the
user can freely write/read data. It’s main purpose in this library is to be used for fast data acquisition;
when the time-critical acquisition has nished, the data can be re-written into a “normal” le, and
formatted in the most suitable way.
Parameters - sectors_cnt: number of consecutive sectors that user wants the swap le to have.
- lename: name of the le that should be assigned for le operations. File name should be in DOS 8.3
(le_name.extension) format. The le 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 no
have to take care of that. The le 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 rst version of this library, le names can be
entered as UPPERCASE string of 11 bytes in length with no dot character between le name and
extension (i.e. “MIKROELETXT” -> MIKROELE.TXT). In this case last 3 characters of the string are
considered to be le extension.
- le_attr: le creation and attributes ags. Each bit corresponds to the appropriate le attribute:
Returns - Number of the start sector for the newly created swap le, if there was enough free space on the
MMC/SD card to create le of required size.
- 0 - otherwise.
Requires MMC/SD card and MMC library must be initialized for le operations. See Mmc_Fat_Init.
Mmc_Fat_Get_Swap_File
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