Ublox TOBY-R2 Series, Руководство по системной интеграции

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TOBY-R2 series - System integration manual
UBX-16010572 - R10 Design-in Page 112 of 151
2.7 Audio interface
2.7.1 Digital audio interface
2.7.1.1 Guidelines for digital audio circuit design
☞
Digital audio interface is not supported by "42" / "82" product versions.
I2S digital audio interface can be connected to an external digital audio device for voice applications.
Any external digital audio device compliant with the configuration of the digital audio interface of the
TOBY-R2 series cellular module can be used, given that the external digital audio device must provide:
 The opposite role: slave or master role, as TOBY-R2 series modules may act as master or slave
 The same mode and frame format: PCM / short synch mode or Normal I2S / long synch mode with
o
data in 2’s complement notation, linear
o
MSB transmitted first
o
data word length = 16-bit (16 clock cycles)
o
frame length = synch signal period:

17-bit or 18-bit in PCM / short alignment mode (16 + 1 or 16 + 2 clock cycles, with the Word
Alignment / Synchronization signal set high for 1 clock cycle or 2 clock cycles)

32-bit in Normal I2S mode / long alignment mode (16 x 2 clock cycles)
 The same sample rate, i.e. synch signal frequency, configurable by AT+UI2S <I2S_sample_rate>
parameter
o
8 kHz
o
11.025 kHz
o
12 kHz
o
16 kHz
o
22.05 kHz
o
24 kHz
o
32 kHz
o
44.1 kHz
o
48 kHz
 The same serial clock frequency:
o
17 x <I2S_sample_rate> or 18 x <I2S_sample_rate> in PCM / short alignment mode, or
o
16 x 2 x <I2S_sample_rate> in Normal I2S mode / long alignment mode

Compatible voltage levels (1.80 V typ.), otherwise it is recommended to connect the 1.8 V digital
audio interface of the module to the external 3.0 V (or similar) digital audio device by means of
appropriate unidirectional voltage translators (e.g. TI SN74AVC4T774 or SN74AVC2T245,
providing partial power down feature so that the digital audio device 3.0 V supply can be also
ramped up before V_INT 1.8 V supply), using the module V_INT output as 1.8 V supply for the
voltage translators on the module side
For the appropriate selection of a compliant external digital audio device, see section 1.10.1 and see
the +UI2S AT command description in the u-blox AT commands manual [2] for further details
regarding the capabilities and the possible settings of I2S digital audio interface of TOBY-R2 series
modules.
An appropriate specific application circuit has to be implemented and configured according to the
particular external digital audio device or audio codec used and according to the application
requirements.
Examples of manufacturers offering compatible audio codec parts are the following:

Maxim Integrated (as the MAX9860, MAX9867, MAX9880A audio codecs)
 Texas Instruments / National Semiconductor