Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 Features description Page 145 of 182
LISA-U2 modules support the Direct Link mode for TCP and UDP sockets. Sockets can be set in Direct
Link mode to establish a transparent end-to-end communication with an already connected TCP or
UDP socket via the serial interface. In Direct Link mode, data sent to the serial interface from an
external application processor is forwarded to the network and vice-versa.
To avoid data loss while using Direct Link, enable HW flow control on the serial interface.
3.4.1 Multiple PDP contexts and sockets
Two PDP context types are defined:
 “external” PDP context: IP packets are built by the DTE, the MT’s IP instance only runs the IP relay
function
 “internal” PDP context: the PDP context (relying on the MT’s TCP/IP stack) is configured,
established and handled via the data connection management packet switched data commands
described in u-blox AT commands manual [2]
Multiple PDP contexts are supported. The DTE can access these PDP contexts either alternatively
through the physical serial port, or simultaneously through the virtual serial ports of the multiplexer
(multiplexing mode MUX), with the following constraints:
 Using the MT’s embedded TCP/IP stack, only 1 internal PDP context is supported. This IP instance
supports up to 7 sockets
 Using only external PDP contexts, it is possible to have at most 3 IP instances (with 3 different IP
addresses) simultaneously. If in addition the internal PDP context is used, at most 2 external PDP
contexts can be activated
Secondary PDP contexts (PDP contexts sharing the IP address of a primary PDP context) are also
supported. Traffic Flow Filters for such secondary contexts shall be specified according to 3GPP TS
23.060 [18].
At most 2 secondary PDP contexts can be activated, since the maximum number of PDP contexts,
both normal and secondary, is always 3.
3.5 FTP
LISA-U2 modules support the File Transfer Protocol and Secure File Transfer Protocol functionalities
via AT commands. Files are read and stored in the local file system of the module. For more details
about AT commands, see the u-blox AT Commands Manual [2].
FTP files can also be transferred using the FTP Direct Link:
 FTP download: the data coming from the FTP server is forwarded to the application processor via
the serial interface (for FTP without Direct Link mode, the data is always stored in the module’s
FFS)
 FTP upload: the data coming from the application processor via the serial interface is forwarded
to the FTP server (for FTP without Direct Link mode, the data is read from the module’s FFS)
When Direct Link is used for a FTP file transfer, only the file content pass through the serial interface,
whereas all the FTP commands handling is managed internally by the FTP application.
Due to the limited size of the FFS module, FTP direct link is useful to transfer files with a size greater
than the FFS.
To avoid data loss while using direct link, enable HW flow control on the serial interface.