AD1938 + ADAU1452 (I/O configuration)

Hello! It is impossible to master the array of information in the technical documentation. I hope for help. There are ADAU1452 + AD1938 boards.
I need to build a chain:

AD1938  -  ADC input 2 channels, I2S output 2 channels.

ADAU1452  -  I2S input 2 channels, I2S output 8 channels.

AD1938  -  I2S input 8 channels, DAC output 8 channels.

Is it possible to use AD1938 both at the input and output of ADAU1452? If yes, please help with the setup.

Important! It is necessary to leave the maximum GPIO free in ADAU1452. And for this, if I understand correctly, you need to use the TDM mode. And organize 8 channels on one DSP output. This is not a problem. But will the AD1938 be able to turn 8 TDM channels into 8 line outputs? Sorry for my English. Thanks!

[edited by: Sashkashka at 4:41 PM (GMT -4) on 11 Jul 2021]
  • +1
    •  Analog Employees 
    on Jul 14, 2021 6:02 PM

    Hello Sashkashka,

    Please look at the eval board for the ADAU1452. Some of your questions can be answered by looking at the user guide. Here is the link to the product page for the eval board.

    EVAL-ADAU1452RevBZ Evaluation Board | Analog Devices

    The AD1938 is designed as a codec and the ADC side can be separated from the DAC side. They can even operate at different sample rate is desired but that is a little tricky to do.

    If you want to use the minimum about of pins on the serial ports you can use TDM8 for both the input and the output of the AD1938. However, you do not have to do that. If the goal is to keep as many GPIO pins on the ADAU1452, then it is the LRCLK pins that you need to use as GPIO. So if you use I2S signals you only have to bring the clocks into one of the serial input ports and one of the serial output ports. There is no internal connection between the input and output ports for clocking. 

    So once the clock is on one set of pins, then the other serial data ports only have to have the SDATA pins connected to the AD1938. Internally on the ADAU1452 you can slave to another serial port's clock pins. So you can bring in clocks to serial input port 0 and slave serial input ports 1,2,& 3 to serial port 0's clocks. The same can be said for the serial output port. 

    If the DSP is a master then you only need one set of clock pins to go to the AD1938 codec. This frees up six LRCLK pins for use as GPIO, 3 on the input side and 3 on the output side. 

    What is important is what sample rate will you be using?

    Dave T

  • Thank you very much! You have answered all possible questions!