User's Manual

TOBY-R2 series - System Integration Manual
UBX-16010572 - R04 System description
Page 53 of 147
1.10 Audio
1.10.1 Digital audio over I
2
S interface
TOBY-R2 series modules include a 4-wire I
2
S digital audio interface (I2S_TXD data output, I2S_RXD data input,
I2S_CLK clock input/output, I2S_WA world alignment / synchronization signal input/output), which 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 [2], +UI2S AT command).
The I
2
S interface can be alternatively set in different modes, by <I2S_mode> parameter of 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 16 clock cycles according to the 17 or 18 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 I
2
S interface can be alternatively set in different roles, by <I2S_Master_Slave> parameter of AT+UI2S:
 Master mode
 Slave mode
The sample rate of transmitted/received words, which corresponds to the I
2
S word alignment / synchronization
signal frequency, can be alternatively 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 modules support I
2
S transmit and I
2
S receive data 16-bit words long, linear, mono (or also dual mono in
Normal I2S mode). Data is transmitted and read in 2’s complement notation. MSB is transmitted and read first.
I
2
S clock signal frequency depends on the frame length, the sample rate and the selected mode of operation:
 17 x <I2S_sample_rate> or 18 x <I2S_sample_rate> in PCM mode (short synchronization signal)
 16 x 2 x <I2S_sample_rate> in Normal I2S mode (long synchronization signal)
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 [2], +UI2S AT command.