User Manual

SARA-R4 series-AT commands manual
UBX-17003787 - R16
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1AT command settings
Page 11 of 401
1AT command settings
u-blox cellular modules provide at least one physical serial interface that is compliant to V.24 [23]. When the
module is powered on, it enters the command mode. For more details on command mode, see Chapter 1.1.
For module and hyper terminal connection and settings see the corresponding evaluation kit user guide.
1.1Definitions
In this document the following naming conventions are used:
• MT (Mobile Terminal) or DCE (Data Communications Equipment): u-blox cellular module
• TE (Terminal Equipment) or DTE (Data Terminal Equipment): terminal that issues the command to the
module
• TA (Terminal Adaptor): the function, integrated in the MT, of supporting AT command interface according
to the applicable standards
• ME (Mobile Equipment): equivalent to MT, it is used to refer to the device itself regardless of the inserted
SIM card
The terms DCE and DTE are used in the serial interface context.
SARA-R4 / SARA-N4
u-blox cellular modules can implement more than one interface between the DTE and the DCE, either
virtual interfaces (multiplexer channels) or physical interfaces (UART, USB, SPI, etc., when available). Each
interface works as specified by the followings definitions. If not differently stated, all the subsequent
descriptions are applicable to each interface. Appendix
B.4 describes the different behaviour among the interfaces in reference to the AT command interface.
See the corresponding module data sheet for the list of available AT command interfaces.
The DCE/MT interface can operate in these modes:
• Command mode: the DCE waits for AT command instructions. The DCE interprets all the characters
received as commands to execute. The DCE may send responses back to the DTE indicating the outcome
of the command or further information without having received any commands by the DTE (e.g. unsolicited
response code - URC). Any communication in the command mode (in both directions) is terminated by the
command line termination character.
• Data mode: the DCE transfers data after having sent the "CONNECT" string; all the characters sent to the
DCE are intended to be transmitted to the remote party. Any further characters received over the serial link
are deemed to be from the remote party, and any characters sent are transmitted to the remote party. The
DCE enters data mode immediately after it makes a Circuit Switched Data (CSD) or Packet Switched Data
(PSD) connection.
• Online command mode: the DCE has a data connection established with a remote party, but treats signals
from the DTE as command lines and sends back responses and unsolicited indications to the DTE.
• AT commands over an IP connection: the DCE is accepting a TCP connection on a specific TCP port. The
DTE can connect via TCP protocol to the port and can send commands over this TCP connection. The DCE
may send responses back to the DTE via the same TCP connection. The communication over IP connection
is denoted by a set of two ports: 1) AT command port; 2) binary data port. The binary data port is used for
the exchange of binary data between the DCE and DTE. For more details, on the configuration of the TCP
ports see +UIFCONF.
SARA-R4 / SARA-N4
The AT commands over IP connection is not supported.
1.1.1Switch from data mode to online command mode
When a data connection is established it is possible to switch from data mode to online command mode (OLCM)
in the following ways:
• with the escape sequence: for more details, see the S2 AT command description
• via a DTR transition: during data mode, the current DTR state is not important, but only its transition.
Furthermore, only the DTR transition from ON to OFF is detected; it can be used to control the switch to
OLCM, or to command mode (the data connection is released). For more details, see the &D AT command
description