LISA-U series - System Integration Manual
UBX-13001118 - R17
Advance information
System description
Page 93 of 190
1.11
Audio Interface
LISA-U120 and LISA-U130 modules provide analog and digital input/output audio interfaces:
Differential analog audio input (
MIC_P
,
MIC_N
) and differential analog audio output (
SPK_P
,
SPK_N
)
4-wire I
2
S digital audio interface (
I2S_CLK
,
I2S_RXD
,
I2S_TXD
and
I2S_WA
)
All LISA-U2 series modules versions except LISA-U200-00S provide two digital input/output audio interfaces:
First 4-wire I
2
S digital audio interface (
I2S_CLK
,
I2S_RXD
,
I2S_TXD
and
I2S_WA
)
Second 4-wire I
2
S digital audio interface (
I2S1_CLK
,
I2S1_RXD
,
I2S1_TXD
and
I2S1_WA
)
Audio signal routing can be controlled by the dedicated AT cUSPM (see the
u-blox AT Commands
Manual
[3]). 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 (see the
u-blox AT Commands Manual
[3] for Audio parameters tuning commands).
1.11.1
Analog Audio interface
LISA-U100, LISA-U110 and LISA-U2 series modules versions do not support 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 see the
u-blox AT
Commands Manual
[3], 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 series Data
Sheet