User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 64 of 116
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).
1.11.1 Analog Audio interface
1.11.1.1 Uplink path (differential analog audio input)
The pins related to the differential analog audio input are:
 MIC_P / MIC_N: Differential analog audio signal inputs (positive/negative). These two pins are provided with
internal series 100 nF capacitors for DC blocking that connect the module pads to the differential input of a
Low Noise Amplifier. The LNA output is internally connected to the digital processing system by an
integrated sigma-delta analog-to-digital converter
The analog audio input is selected when the parameter <main_uplink> in AT+USPM command is set to
“Headset microphone”, “Handset microphone” or “Hands-free microphone”: the uplink analog path profiles
use the same physical input but have different sets of audio parameters (for more details please refer to u-blox
AT Commands Manual [2], AT+USPM, AT+UMGC, AT+UUBF, AT+UHFP commands).
There is no microphone supply pin available on the module: an external low noise LDO voltage regulator should
be added to provide a proper supply for a microphone.
Detailed electrical characteristics of the differential analog audio input can be found in the LISA-U1/LISA-H1
series Data Sheet [1].
1.11.1.2 Downlink path (differential analog audio output)
The pins related to the differential analog audio output are:
 SPK_N / SPK_P: Differential analog audio signal output (positive/negative). These two pins are internally
directly connected to the differential output of a low power audio amplifier, for which the input is internally
connected to the digital processing system by to an integrated digital-to-analog converter.
The analog audio output is selected when the parameter <main_downlink> in AT+USPM command is set to
“Normal earpiece”, “Mono headset” or “Loudspeaker”: the downlink analog path profiles use the same
physical output but have different sets of audio parameters (for more details please refer to u-blox AT
Commands Manual [2], AT+USPM, AT+USGC, AT+UDBF, AT+USTN commands).
The differential analog audio output can be directly connected to a headset earpiece or handset earpiece but is
not able to drive an 8  speaker.
Detailed electrical characteristics of the high power differential audio output can be found in the
LISA-U1/LISA-H1 series Data Sheet [1].
Warning: excessive sound pressure from headphones can cause hearing loss.