Integration Manual

TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R26 System description
Page 57 of 162
1.10 Audio
1.10.1 Digital audio over I
2
S interface
I
2
S digital audio interface is not available on MPCI-L2 modules.
I
2
S digital audio interface is not supported by TOBY-L2 modules ’00‘, ’01‘, ’60‘, ‘L201-02’, ‘L220-62’ vers.
TOBY-L2 series modules include a 4-wire I
2
S digital audio interface (I2S_TXD data output, I2S_RXD data input,
I2S_CLK clock output, I2S_WA world alignment / synchronization signal output) that can be configured by AT
command for digital audio communication with external digital audio devices as an audio codec (for more details
see the u-blox AT Commands Manual [3], +UI2S AT command).
The I
2
S interface can be set to two modes, by the <I2S_mode> parameter of the AT+UI2S command:
 PCM mode (short synchronization signal): I
2
S word alignment signal is set high for 1 or 2 clock cycles for the
synchronization, and then is set low for 31 or 30 clock cycles according to the 32 clock cycles frame length.
 Normal I
2
S mode (long synchronization signal): I
2
S word alignment is set high / low with a 50% duty cycle
(high for 16 clock cycles / low for 16 clock cycles, according to the 32 clock cycles frame length).
The modules support I
2
S master role only: I2S_CLK clock and I2S_WA world alignment / synchronization signal
are generated by the module.
The sample rate of transmitted/received words, which corresponds to the I
2
S word alignment / synchronization
signal frequency, can be set by the <I2S_sample_rate> parameter of AT+UI2S to:
 8 kHz
 16 kHz
The modules support I
2
S transmit and I
2
S receive data 16-bit words long, linear, mono. Data is transmitted and
read in 2’s complement notation. MSB is transmitted and read first.
I
2
S clock signal frequency is set to 32 x <I2S_sample_rate>: the frame length, which corresponds to the I
2
S word
alignment / synchronization signal period, is 32 I
2
S clock cycles long.
For the complete description of the possible configurations and settings of the I
2
S digital audio interface for
PCM and Normal I
2
S modes refer to the u-blox AT Commands Manual [3], +UI2S AT command.
The internal audio processing system is summarized in Figure 26: external digital audio devices can be interfaced
directly to the digital signal processing part via the I
2
S digital interface. Audio processing can be controlled by AT
commands: see Audio Interface and Audio Parameters Tuning sections in the u-blox AT Commands Manual [3].
ECHFP
To
Radio TX
From
Radio RX
RES
NS
DRCLPF EQAGC
I2S_RXD
I2S_TXD
Volume &
Mute
CNG
AGCEQ
LPF
DRC
NSHPF
Volume &
Mute
PCM
Player
Tone
Generator
Legend:
EC = Echo Cancellation
RES = Residual Echo Suppression
NS = Noise Suppression
LPF = Low Pass Filter
HPF = High Pass Filter
EQU = Equalizer
AGC = Additional Gain Control
DRC = Dynamic Range
Compression
CNG = Comfort Noise Generator
TOBY-L2
Figure 26: TOBY-L2 modules internal audio processing system block diagram
The internal audio processing system of TOBY-L2 modules does not support the side-tone.