Technical information

Improved OEM Features
1-12 AT Commands Reference Manual August 5, 2008
The G24 operation modes switching is shown in Figure 1-2.
Figure 1-2: G24 Operation Modes Switching
Note:
1
AT&D settings = 2 or 3. The operation closes the actual FTP connection and switches
G24 to command mode.
AT&D settings = 1 does not affect.
Established FTP connection can be closed when G24 is in command mode by AT+FTPCLOSE
command or by changing DTR line status from ON to OFF when data transfer operations are
performed (G24 is in online data mode).
Manage Remote File System
When FTP connection is established, the user is able to manage file system on the remote FTP
server, like create, remove, change directory, rename or delete a file. The following FTP
commands are used for remote file system management purpose.
+FTPCWD - changes the working directory on a remote server.
+FTPMKD - creates a new directory on a remote server.
+FTPRMD - removes existing directory on a remote server.
+FTPPWD - returns actual working directory name from a remote server.
+FTPCDUP - changes working directory on a remote server, up to parent directory.
+FTPDEL - deletes a file on a remote server.
+FTPREN - renames a file on a remote server.
File Transfer Operations
The file transfer operation allows the user to transfer a file over an established FTP connection.
To avoid end-of-file detection problem for user in download case and for G24 in upload case,
G24 implements a special format of transferred files over FTP connection. The format proposed
"escaping" one of the ASCII symbols of a file context and using the "escaped" symbol as
end-of-file marker. An escaping algorithm is described below.
The algorithm defines two special characters: EOF (end-of-file character) and ESC (escape
character). EOF symbol is a hexadecimal 0x03 (decimal 3) ASCII ETX symbol and ESC symbol
is a hexadecimal 0x10 (decimal 16) ASCII DLE symbol - not to be confused with the ASCII
ESCape character.
To encode a file to FTP File Transfer Format, the user or G24 will read each data byte from the
source file and will perform the following operations: