Analog/Digital(I2S) selectro for ADAU 1702

Hello Markus,

A suitable circuit is shown below. It runs on the ADAU17MINIZ board. A Buffer Gate converts the GPIO input to an integer (0-1 LSB), suitable for controlling the slew MUXes. Also shown is a volume control driven by the DC pot on the mini eval board.

Normally the GPIO input is high, which selects the audio ADCs. Pressing S4 grounds the GPIO input, selecting the I2S inputs. I believe your description of Left and Right I2S channels is correct. Be sure to set the -1702 control registers in order to properly map your 1702's multipurpose pins to the I2S and GPIO functions being used. A sample setup is shown here for the -1701MINZ board. If you're using a -1701 mini eval board you can download the project file below and run it directly.

To successfully input I2S audio to your -1702, you also need to supply its master clock (MCLK) from your Bluetooth module -- since the -1702 has no sample rate converter, the two chips must synchronize. This is discussed in various posts on the forum, such as https://ez.analog.com/message/110520#110520

Bob

Hi Bob,

Thanks for the bright and clear answer!

I also wonder if someone has any experience of adding SPDIF to ADAU1701? I have a digital audio receiver from TI P/N DIR9001 that I would like to connect to ADAU1701 via I2S. DIR9001 can be used standalone and I wonder how to connect the interface pins to ADAU1701.

I will then have two I2S stereo inputs to ADAU1701 - one from a BT-module and one from DIR9001. Only one of the inputs shall be selected at a time. Is this possible?

Best regards

Markus

Hi Markus,

The ADAU1701 has multiple I2S data input pins but only one set of BCLK/LRCLK pins. Also, it has no ASRCs. This makes it a bit tricky to select between your two sources.

Probably the simplest solution to this problem would be to get a standalone ASRC in the system that would sit between the two audio sources and the SigmaDSP and re-clock the I2S streams to the rate of the ADAU1701. You could then have both sources synchronized to the same clocks, requiring only one set of clocks from the ADAU1701 to the ASRC (you can set up the serial output port on the ADAU1701 to a master, then route those clock signals back to both its serial input port - configured as a slave - and to the ASRC).

Then you could simply select between both sources with a data multiplexer (a.k.a. stereo switch) inside SigmaStudio.

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Thank you,
EZ Admin