Mikroelektronika MIKROE-724 データシート

402

mikoBasic PRO for dsPIC30/33 and PIC24

MikroElektronika

Prototype

sub function Mmc_Fat_Get_Swap_File(dim sectors_cnt as longword, dim byref

filename as string[11], dim file_attr as byte) as longword

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. It’s main purpose in 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. 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 no

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 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:

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.

- otherwise.

Requires

MMC/SD card and MMC library must be initialized for file operations. See Mmc_Fat_Init.

Mmc_Fat_Get_Swap_File

Bit

Mask

Description

0x01

Read Only

0x02

Hidden

0x04

System

0x08

Volume Label

0x10

Subdirectory

0x20