how to set AD1938 if I need AD1938 ADC&DAC are slave


     I have a question :now i use ADSP2189 to singal process and AD1938 to AD&DA convert,if I set ADSP21489 is slave ,and AD1938 ADC(master) input single,DAC(slave) output single are no problem, but if i use ADSP21489 to master  control AD1938,the AD1938 DAC no output, i try it(ADSP21489) to produce sin singal ,and AD1938 DAC output, but DAC no singal output,

    could you give me  some idea? or tell me how set AD1938 when need AD1938 is slave status?

     ths so much!

  • 0
    •  Analog Employees 
    on Mar 13, 2019 2:53 PM


    First I need to say that I am the support person for the AD1938 and the SigmaDSP but not for the SHARC DSP. So I cannot help you with the SHARC code. 

    I suggest you look at the LRCLK, BITCLK and SDATA using an oscilloscope so you can see what is being sent out by either the SHARC or the Codec. This always helps to see what the problem is. You can look at this post I wrote to see how to look at these waveforms. 

    I have a few questions:

    Can you tell me what the sampling rates are?

    It is usually best to have the ADC be the master and the DAC operate as a slave for timing margin reasons. This is important if you are going to run at 192kHz fs. 

    What is the master clock frequency going into the Codec and where is it coming from?

    Are you using I2S or TDM? If TDM then how many channels and what are the details of the format?

    Then I could use the register settings of the Codec. 

    Is the hardware your own hardware or an Evaluation board?

    Sorry for all the questions but I need to look at the entire picture and understand what you need. 

    Dave T