16 Input / 16 Output Mixer with AD1939 + AD1974

Hi there,

I am designing a digital audio mixer with 16 audio input channels and 16 output channels. A combined DSP/ARM provides processing and Ethernet capabilities.

In order to speed up the process, I'm using a module that includes an OMAPL138. In the module interface I have got available up to 8 McASP channels. Using I2S I could not transmit all the 32 channels. Thus, I would need to use a TDM8 or TDM16 format. TDM 8 will reduce the emissions.   

I want to use the AD1939 codec but I would need 4 extra inputs. I was thinking on using a AD1974 to provide those extra inputs but I'm in doubt of what would be the best way of connecting the codecs.

Would it be possible/right to connect two AD1939 in parallel, each of them with their own auxiliary AD1974, like in the diagram? Is the diagram correct, using ASDATA1 and ASDATA2, in I2S mode or is there a better way?

Note: I have not connected the 12.288MHz as it seems that is not really necessary for the McASP ports.

Would it be necessary to use some kind of clock buffering/distribution?

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  • Hello Dave,

    Thank you for your fast response!

    It is strange you cannot see the attachment. I have tried and can see it. Anyway, I attach the final diagram in case is of any use to anyone else.

    About the LRCLK... you are right! I had a comment on my notes (written some time ago) about that section of the OMAP saying the option to generate a frame sync from the bit clock could only make sense if acting as a master... I happily ignored it yesterday during the simplifying frenzy.

    Thank you again,

    Jordi

Reply
  • Hello Dave,

    Thank you for your fast response!

    It is strange you cannot see the attachment. I have tried and can see it. Anyway, I attach the final diagram in case is of any use to anyone else.

    About the LRCLK... you are right! I had a comment on my notes (written some time ago) about that section of the OMAP saying the option to generate a frame sync from the bit clock could only make sense if acting as a master... I happily ignored it yesterday during the simplifying frenzy.

    Thank you again,

    Jordi

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