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1.6.2 SD File Operations
The SD card is treated as a formatted disk. The supported file systems are: FAT-‐12, FAT-‐16 and
FAT32. The user data is stored in files. Besides the ezLCD, the files may be read or written by SD
Reader/Writer connected to any computer.
Formatting the SD Card.
In order to perform File Operations, the
SD Card has to be formatted in FAT-‐32, FAT-‐16 or
FAT12
.
The ezLCD will not perform any File Operations on the unformatted SD Card, nor it will do that
on the card formatted with the file system other than FAT-‐32, FAT-‐16 or FAT-‐12.
The SD card can be formatted:
·∙ outside the ezLCD by using SD Reader/Writer connected to the PC, or
·∙ inside the ezLCD by sending
SD_FORMAT
command to the ezLCD, or
·∙ inside the ezLCD by using SDformat.exe supplied with the
SD Source Code Examples
.
About the supported file systems
FAT12
FAT16
FAT16
Full Name
File Allocation Table
12-bit version
16-bit version
32-bit version
Introduced
1977
July 1988
August 1996
Max file size
32 MB
2 GB
4 GB
Max number of files
4,077
65,517
268,435,437
Max volume size
32 MB
2 GB
8TB
Summary of the SD File Operations commands.
SD_FORMAT
Formats the SD in the specified file system.
SD_FILE_LIST
Gets the list of files and sub-‐directories which reside in the specified SD Directory.
SD_FILE_OPEN
Opens an existing SD Flash file for reading or writing. File Position Index is set to 0. Temporary
disables the Touch Screen. The Touch Screen will be automatically re-‐enabled when all files are
closed. In order to open non-‐existing, new file, use the command
SD_FILE_CREATE
SD_FILE_CREATE
Creates a new SD Flash file and opens it for writing. File Position Index is set to 0. Temporary
disables the Touch Screen. The Touch Screen will be automatically re-‐enabled when all files are
closed.
SD_FILE_CLOSE
Closes SD Flash file. Re-‐enables the touch screen if no other SD files are opened.
Содержание ezLCD-405
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