User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information System description
Page 57 of 206
SARA-G3 modules’ auxiliary UART interface can be configured in AT command mode by means of the AT+USIO
command (for more details see Table 12 and the u-blox AT Commands Manual [3]), so that:
x the cellular module waits for AT command instructions and interprets all the characters received over the
auxiliary UART interface as commands to execute
x the auxiliary UART interface provides RS-232 functionality conforming to the ITU-T V.24 Recommendation
(more details available in ITU Recommendation [10]), with CMOS compatible signal levels: 0 V for low data
bit or ON state, and 1.8 V for high data bit or OFF state (for detailed electrical characteristics see SARA-G3
series Data Sheet [1])
x the cellular module is designed to operate as a modem, which represents the Data Circuit-terminating
Equipment (DCE) according to ITU-T V.24 Recommendation [10]: the application processor connected to the
module through the auxiliary UART interface represents the Data Terminal Equipment (DTE)
x Software flow control and None flow control can be set (see u-blox AT Commands Manual [3], &K, +IFC, \Q
AT commands), with default setting None flow control
x 2400, 4800, 9600, 19200, 38400, 57600 and 115200 b/s baud rate can be set (see u-blox AT Commands
Manual [3], +IPR), with default setting 115200 b/s
x 8N1, 8N2, 8E1, 8O1, 7E1 or 7O1 frame format can be set (see u-blox AT Commands Manual [3], +ICF), with
default setting 8N1
The signal names of SARA-G3 series modules’ auxiliary UART interface conform to the ITU-T V.24
Recommendation [10]: e.g. the TXD_AUX line represents the data transmitted by the DTE (application
processor data line output) and received by the DCE (module data line input).
Hardware flow control is not supported on the auxiliary UART interface
Automatic baud rate detection (autobauding) and automatic frame recognition are not supported on the
auxiliary UART interface
Data mode and Online command mode are not supported over the Auxiliary UART interface, so that for example
the ATD command for data call, the ATO command for online data state resuming, the AT+CGDATA command
for data state entering and the AT+USODL command for direct link are not supported, but Mobile Originated
voice call can be accepted, Mobile Terminated voice call can be triggered and voice call hang-up can be done
over the auxiliary UART interface.
The auxiliary UART interface provides only the RXD_AUX data output and the TXD_AUX data input signals, so
that for example the AT&C, AT&D and AT&S commands have no effect on the interface, since there are no DCD,
DTR and DSR lines available.
When the auxiliary UART interface is configured in AT command mode by means of the AT+USIO command (for
more details see Table 12 and the u-blox AT Commands Manual [3]), then both the UART and the auxiliary UART
interfaces can receive AT commands in parallel. The UART can be used for AT commands, data communication
and Multiplexer functionalities, while auxiliary UART can be used for for AT commands only.
See the “Multiple AT command interfaces” appendix in the u-blox AT Commands Manual [3], for further details
regarding multiple AT command interfaces general usage and related AT command profile configurations.
The power saving configuration is controlled by the AT+UPSV command, which can be retrieved over the
auxiliary UART interface as over the UART interface: it sets the module power saving configuration and also the
interface behavior in relation to the power saving.
For further details regarding power saving configurations, see the section 1.9.1.4 and the u-blox AT Commands
Manual [3], +UPSV AT command.