EarthLCD ezLCD-405, Manual

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© 2016 Earth Computers Tech. Inc.
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.