Integration Manual
SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 System description Page 38 of 157
1.9 Data communication interfaces
SARA-R4/N4 series modules provide the following serial communication interface:
USB interface: Universal Serial Bus 2.0 compliant interface available for the communication with a host
application processor (AT commands, data, FW update by means of the FOAT feature), for FW update
by means of the u-blox dedicated tool and for diagnostics. See section 1.9.2.
SPI interface: Serial Peripheral Interface available for communication with an external compatible device.
See section 1.9.3.
SDIO interface: Secure Digital Input Output interface available for communication with a compatible
device. See section 1.9.4.
DDC interface: I
2
C bus compatible interface available for the communication with u-blox GNSS
positioning chips or modules and with external I
2
C devices. See section 1.9.5.
1.9.1 UART interface
1.9.1.1 UART features
The UART interface is a 9-wire 1.8 V unbalanced asynchronous serial interface available on all the SARA-
R4/N4 series modules, supporting:
AT command mode
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Data mode and Online command mode
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Multiplexer protocol functionality
FW upgrades by means of the FOAT feature (see 1.13.7)
☞ The UART is available only if the USB is not enabled as AT command / data communication interface:
UART and USB cannot be concurrently used for this purpose.
UART interface provides RS-232 functionality conforming to the ITU-T V.24 Recommendation [5], 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
electrical characteristics see the SARA-R4/N4 series Data Sheet [1]), providing:
data lines (RXD as output, TXD as input)
hardware flow control lines (CTS as output, RTS as input)
modem status and control lines (DTR as input, DSR as output, DCD as output, RI as output)
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For the definition of the interface data mode, command mode and online command mode see SARA-R4/N4 series AT Commands Manual [1]