LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 90 of 175
The I
2
S interface can be set to two configurations, by the <I2S_Master_Slave> parameter of AT+UI2S:
Master mode
Slave mode
The sample rate of transmitted/received words can be set, by the <I2S_sample_rate> parameter of AT+UI2S, to:
8 kHz
11.025 kHz
12 kHz
16 kHz
22.05 kHz
24 kHz
32 kHz
44.1 kHz
48 kHz
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
<main_uplink> has to be properly set to select:
o
the first I
2
S interface (using
I2S_RXD
module input)
o
the second I
2
S interface (using
I2S1_RXD
module input)
<main_downlink> has to be properly set to select:
o
the first I
2
S interface (using
I2S_TXD
module output)
o
the second I
2
S interface (using
I2S1_TXD
module output)
Parameters of digital path can be configured and saved as the normal analog paths, using appropriate path
parameter as described in the
u-blox AT Commands Manual
[2], +USGC, +UMGC, +USTN AT command. Analog
gain parameters are not used.
The I
2
S receive data input and the I
2
S transmit data output signals can use the following resources:
Digital filters and digital gains are available in both uplink and downlink direction. They can be properly
configured by the AT commands
Ringer tone and service tone are mixed on the TX path when active (downlink)
The HF algorithm acts on I
2
S path
See the
u-blox AT Commands Manual
[2] (AT+UI2S command) for the possible settings of I
2
S interface.
1.11.1
I
2
S interface - PCM mode
Main features of the I
2
S interface in PCM mode:
I
2
S runs in PCM - short alignment mode (configurable by AT commands)
I
2
S word alignment signal can be configured to 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48 kHz
I
2
S word alignment toggles high for 1 or 2 CLK cycles of synchronization (configurable), then toggles low for
16 CLK cycles of sample width. Frame length can be 1 + 16 = 17 bits or 2 + 16 = 18 bits
I
2
S clock frequency depends on frame length and <sample_rate>. Can be 17 x <sample_rate> or 18 x
<sample_rate>
I
2
S transmit and I
2
S receive data are 16 bit words long with the same sampling rate as I
2
S word alignment,
mono. Data is in 2’s complement notation. MSB is transmitted first