SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
System description
Page 40 of 188
1.9
Serial interfaces
SARA-G3 and SARA-U2 series modules provide the following serial communication interfaces:
UART interface: 9-wire unbalanced 1.8 V asynchronous serial interface available for AT commands, data
communication, FW upgrades by means of the FOAT feature (see 1.9.1)
Auxiliary UART interface (not supported by SARA-U2 series): 3-wire unbalanced 1.8 V asynchronous serial
interface available for FW upgrades by means of the u-blox EasyFlash tool and for diagnostic (see 1.9.2)
USB interface (not supported by SARA-G3 series): High-Speed USB 2.0 compliant interface available for AT
commands, data communication, FW upgrades by means of the FOAT feature, FW upgrades by means of
the u-blox EasyFlash tool and for diagnostic (see 1.9.3)
DDC interface (not supported by SARA-G300 / SARA-G310): I
2
C compatible 1.8 V interface available for the
communication with u-blox positioning chips / modules and additionally, except for SARA-G3 series, with
other external I
2
C devices as an audio codec (see 1.9.4)
1.9.1
Asynchronous serial interface (UART)
1.9.1.1
UART features
The UART interface is a 9-wire 1.8 V unbalanced asynchronous serial interface available for AT commands and
for packet-switched / circuit-switched data communication on all the SARA-G3 and SARA-U2 series modules.
The 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
and
SARA-U2 series Data Sheet
SARA-G3 and SARA-U2 series modules are designed to operate as a 2G or 3G cellular modem, which represents
the Data Circuit-terminating Equipment (DCE) according to the
ITU-T V.24 Recommendation
[10]. The
application processor connected to the module through the UART interface represents the Data Terminal
Equipment (DTE).
The signal names of SARA-G3 and SARA-U2 series modules’ UART interface conform to the
ITU-T V.24
Recommendation
[10]: e.g. the
TXD
line represents the data transmitted by the DTE (application
processor data line output) and received by the DCE (module data line input).
All flow control handshakes are supported by the UART interface and can be set by appropriate AT commands
(see
u-blox AT Commands Manual
[3], &K, +IFC, \Q AT commands): hardware flow control (RTS/CTS), software
flow control (XON/XOFF), or none flow control.
Hardware flow control is enabled by default.
SARA-G3 modules support the autobauding: the baud rate automatic detection is performed each time the DTE
sends AT commands. After the detection the module works at the detected baud rate and the baud rate can be
runtime changed by the DTE or by AT command (see
u-blox AT Commands Manual
[3], +IPR command).
SARA-U2 modules support only the one-shot autobauding: the baud rate automatic detection is performed only
once, at module start up. After the detection the module works at the detected baud rate and the baud rate can
only be changed by AT command (see
u-blox AT Commands Manual
[3], +IPR command).
SARA-G3 modules’ autobauding and SARA-U2 modules’ one-shot autobauding are enabled by default.
