User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information System description
Page 66 of 206
1.10.2 Digital audio interface
SARA-G340, SARA-G350 and SARA-U2 modules provide one 1.8 V bidirectional 4-wire (I2S_TXD data output,
I2S_RXD data input, I2S_CLK clock, I2S_WA world alignment) I
2
S digital audio interface that can be used for
digital audio communication with external digital audio devices as an audio codec.
The I
2
S interface can be set to two modes, by the <I2S_mode> parameter of the AT+UI2S command:
x PCM mode
x Normal I
2
S mode
The I
2
S interface can be set to two configurations, by the <I2S_Master_Slave> parameter of AT+UI2S:
x Master mode
x Slave mode
SARA-G340 and SARA-G350 modules do not support I
2
S slave mode: module acts as master only.
The sample rate of transmitted/received words can be set, by the <I2S_sample_rate> parameter of AT+UI2S, to:
x 8 kHz
x 11.025 kHz
x 12 kHz
x 16 kHz
x 22.05 kHz
x 24 kHz
x 32 kHz
x 44.1 kHz
x 48 kHz
SARA-G340 and SARA-G350 modules do not support the <I2S_sample_rate> parameter of AT+UI2S: the
sample rate is fixed at 8 kHz only.
The <main_uplink> and <main_downlink> parameters of the AT+USPM command must be properly configured
to select the I
2
S digital audio interfaces paths (for more details, see the u-blox AT Commands Manual [3]):
x <main_uplink> must be properly set to select:
o the I
2
S interface (using I2S_RXD module input)
x <main_downlink> must be properly set to select:
o the I
2
S interface (using I2S_TXD module output)
Parameters of digital path can be configured and saved as described in the u-blox AT Commands Manual [3],
+USGC, +UMGC, +USTN AT commands. Analog gain parameters are not used when digital path is selected.
The I
2
S receive data input and the I
2
S transmit data output signals are respectively connected in parallel to the
analog microphone input and speaker output signals, so resources available for analog path can be shared:
x Digital filters and digital gains are available in both uplink and downlink direction
x Ringer tone and service tone are mixed on the TX path when active (downlink)
x The HF algorithm acts on I
2
S path
See the u-blox AT Commands Manual [3]: AT+UI2S command for possible settings of I
2
S interface.
I
2
S pins of SARA-G3 modules product versions “02” onwards can be used additionally for diagnostic.