SARA-G3 series - System Integration Manual
UBX-13000995 - R06
Objective Specification
System description
Page 65 of 218
As additional improvement for the GNSS receiver performance, the
V_BCKP
supply output of SARA-G350
modules can be connected to the
V_BCKP
backup supply input pin of u-blox positioning chips and
modules to provide the supply for the GNSS real time clock and backup RAM when the
VCC
supply of
the wireless module is within its operating range and the
VCC
supply of the GNSS receiver is disabled.
This enables the u-blox positioning receiver to recover from a power breakdown with either a hot start or
a warm start (depending on the duration of the GNSS receiver
VCC
outage) and to maintain the
configuration settings saved in the backup RAM.
1.10
Audio interface
SARA-G300 and SARA-G310 modules do not support audio interface.
SARA-G350 modules provide one analog audio interface and one digital audio interface that can be
selected and set by the dedicated AT cUSPM (refer to
u-blox AT Commands Manual [2]):
this command allows setting the audio path mode, composed by the uplink audio path and the downlink
audio path.
Each uplink path mode defines the physical input (i.e. the analog or the digital audio input) and the set
of parameters to process the uplink audio signal (uplink gains, uplink digital filters, echo canceller
parameters). For example the “Headset microphone” uplink path uses the differential analog audio input
with the default parameters for the headset profile.
Each downlink path mode defines the physical output (i.e. the analog or the digital audio output) and the
set of parameters to process the downlink audio signal (downlink gains, downlink digital filters and
sidetone). For example the “Mono headset” downlink path uses the differential analog audio output with
the default parameters for the headset profile.
The set of parameters to process the uplink or the downlink audio signal can be changed with dedicated
AT commands for each uplink or downlink path and then stored in two profiles in the non volatile memory
(refer to
u-blox AT Commands Manual [2] for Audio parameters tuning commands).
1.10.1
Analog audio interface
1.10.1.1
Uplink path
SARA-G350 pins related to the analog audio uplink path are:
MIC_P / MIC_N
: Differential analog audio signal inputs (positive/negative). These two pins are
internally directly connected to the differential input of an integrated Low Noise Amplifier, without any
internal series capacitor for DC blocking. The LNA output is internally connected to the digital
processing system by an integrated sigma-delta analog-to-digital converter
MIC_BIAS
: Supply output for an external microphone. The pin is internally connected to the output of
a low noise LDO linear regulator provided with proper internal bypass capacitor to guarantee stable
operation of the linear regulator
MIC_GND
: Local ground for the external microphone. The pin is internally connected to ground as a
sense line as the reference for the analog audio input
