LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 89 of 175
1.11
Audio Interface
All LISA-U2 series modules provide two bidirectional 4-wire I
2
S digital audio interfaces for connecting to remote
digital audio devices:
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 command +USPM (see the
u-blox AT Commands
[2]). This command allows setting the audio path mode, composed by the uplink audio path and the
downlink audio path.
Each uplink and downlink path mode defines the physical input / output, the set of parameters to process the
uplink audio signal (uplink gains, uplink digital filters, echo canceller parameters) and the set of parameters to
process the downlink audio signal (downlink gains, downlink digital filters and sidetone).
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
[2] for audio parameters tuning commands).
LISA-U2 series modules can act as I
2
S master or I
2
S slave. In master mode the word alignment and clock signals of
the I
2
S digital audio interface are generated by the module. In slave mode these signal must be generated by the
remote device.
Table 40 lists the signals related to digital audio function.
Name
Description
Remarks
I2S_TXD
I
2
S transmit data
Module output
I2S_RXD
I
2
S receive data
Module input
I2S_CLK
I
2
S clock
Module output in master mode
Module input in slave mode
I2S_WA
I
2
S word alignment
Module output in master mode
Module input in slave mode
I2S1_TXD
Second I
2
S transmit data
Module output
I2S1_RXD
Second I
2
S receive data
Module input
I2S1_CLK
Second I
2
S clock
Module output in master mode
Module input in slave mode
I2S1_WA
Second I
2
S word alignment
Module output in master mode
Module input in slave mode
CODEC_CLK
Digital clock output
Digital clock output for external audio codec
Configurable to 26 MHz or 13 MHz
Table 40: Digital audio interface pins
The I
2
S interfaces and
CODEC_CLK
pins ESD sensitivity rating is 1 kV (Human Body Model according to
JESD22-A114F). Higher protection level could be required if the lines are externally accessible on the
application board. Higher protection level can be achieved by mounting a general purpose ESD protection
(e.g. EPCOS CA05P4S14THSG varistor array) on the lines connected to the I
2
S interfaces pins, close to
accessible points, and a low capacitance (i.e. less than 10 pF) ESD protection (e.g. AVX USB0002) on the
line connected to
CODEC_CLK
pin, close to accessible point.
The I
2
S interface can be set to two modes, by the <I2S_mode> parameter of the AT+UI2S command:
PCM mode
Normal I
2
S mode
