Integration Manual

LISA-U series - System Integration Manual
3G.G2-HW-10002-A3 Preliminary System description
Page 84 of 160
1.11.2.2 I
2
S interface - Normal I
2
S mode
Normal I
2
S supports:
 16 bits word
 Mono interface
 Configurable sample rate: 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48 kHz
Main features of I
2
S interface in normal I
2
S mode:
 I
2
S word alignment signal always runs at <sample_rate> and synchronizes 2 channels (timeslots on word
alignment high, word alignment low)
 I
2
S transmit data is composed of 16 bit words, dual mono (the words are written on both channels). Data
are in 2’s complement notation. MSB is transmitted first. The bits are written on I
2
S clock rising or falling
edge (configurable)
 I
2
S receive data is read as 16 bit words, mono (words are read only on the timeslot with WA high). Data is
read in 2’s complement notation. MSB is read first. The bits are read on the I
2
S clock edge opposite to I
2
S
transmit data writing edge (configurable)
 I
2
S clock frequency is 16 bits x 2 channels x <sample_rate>
The modes are configurable through a specific AT command (refer to the related chapter in u-blox AT
Commands Manual [3], +UI2S AT command) and the following parameters can be set:
 MSB can be 1 bit delayed or non-delayed on I
2
S word alignment edge
 I
2
S transmit data can change on rising or falling edge of I
2
S clock signal (rising edge in this example)
 I
2
S receive data are read on the opposite front of I
2
S clock signal
1.11.2.3 I
2
S interface application circuits
LISA-U series I
2
S digital audio interfaces can be connected to an external digital audio device for voice
applications. The external digital audio device must be properly configured according to the wireless module
configuration, with opposite role (i.e. master vs. slave), same mode (i.e. PCM mode or Normal I
2
S mode), same
sample rate and same voltage level.
Figure 46 shows an application circuit with a generic digital audio device.
43
I2S_CLK
41
I2S_WA
I
2
S Clock
I
2
S Word Alignment
LISA-U120-xx
LISA-U130-xx
LISA-U2xx-01
42
I2S_TXD
44
I2S_RXD
I
2
S Data Input
I
2
S Data Output
GND
GND
1.8 V Digital
Audio Device
Figure 46: I
2
S interface application circuit with a generic digital audio device
Figure 47 shows an application circuit for I
2
S digital audio interfaces of LISA-U2xx-01 modules, providing voice
capability using an external audio voice codec. DAC and ADC integrated in the external audio codec respectively
converts an incoming digital data stream to analog audio output through a mono amplifier and converts the
microphone input signal to the digital bit stream over the digital audio interface.