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Multiplexing Audio Data for continuous Analog Inputs

Other Parts Discussed in Thread: PCM3168A, TMS320C6748

Hello,

We are having continuous Analog input data coming from 3 different channels. We would like to process them via CODEC to single McBSP port on DSP without loosing any data. Please suggest any approach and any specific CODEC that could be used for this prupose. For single channel we were using PCM3010DB.

We are not limited to only use above mentioned CODEC, but I would like to avoid just multiplexing the data without processing them all.

Thanks,

Awais

  • Hi, Muhammad,

    I recommended the PCM3168A in a different post, this device could send the data from up to 6 ADCs into a single TDM stream. From the information shared, I think this device would satisfy the needs, can you please provide more comments about the application?. if three channels are required, you would need TDM as I²S format only supports two channels.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Hi Diego,

    Thanks for the details.

    Our application is taking input data to the mixer and output of mixer is providing data at audio frequencies with sampling frequency (fs) of 96Khz. Previously we only have 1 ADC and we were using its 2 channels (on VINR and VINL), we need to add 2 more ADCs to provide a total of 6 channels.

    I have looked at Table 11 for PCM3168A, Seems like the one you are referring is providing TDM data at D1OUT but only at 48KHz of fs. For 96KHz seems like we need 2 DIN and 2 DOUT, can we achieve this by using both McBSP interfaces on DSP (there are 2 McBSP channels on our DSP)? Please suggest us the way to use this mode at 96KHz.

    We would appreciate if you could provide the reference schematic where PCM3168A is interfaced via TDM with any DSP for multi-channel mode at 96KHz? This chip has different modes and configurations, we to make sure that we will configure it corrently. Our DSP is TMS320C6748.


    Kind regards,

    Muhammad Awais

  • Hi Diego,

    I will be looking forward to your reply.


    Thanks,

    Muhammad Awais
  • Hi, Muhammad,

    Thanks for the additional information. Your assumption is correct, if 96KHz is used, then DOUT1 and DOUT2 will be necessary to output the six channels, three on each signal. Two interfaces would be required on the processor side, they can share the same BCLK and LRCK clocks, only the digital signals will be specific for each port. Please consider that one of the ports on the processor should be configured as Master of the audio bus.

    Assuming the PCM3168A is configured by hardware in TDM dual-speed mode with 96KHz sampling rate, the connection with a processor with two audio interfaces  can be as follows:


    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Thanks Diego for the description along with the schematic sketch. It is now much clear to me. I have created the CODEC schematic (will show you later after complete interface with DSP).  

    On PCM3168a it is clear now but the signals on DSP McBSP is a bit different in description. For example previously we were using SCKI from 24MHz oscillator. Do we change oscillator to 24.567MHz, I am asking his because I couldn't find any similar pin on McBSP that can be used for this purpose.

    Here is how the DSP side McBSP signals are, can you please update your schematic sketch accordingly to these DSP signals?

    Thanks for your support.

    Kind regards,

    Muhammad Awais

  • Hello Diego,P

    I have myself updated the connectivity diagram between CODEC to McBSP lines. Please have a look on the snapshot given below and kindly verify if this is good to go. In our previous design we were connecting 24MHz but now changed to provide the SCKI to 24.576MHz from external oscillator. 

    Please let me know if we need to change any connection on this.

    Kind regards,

    Muhammad Awais

  • Hello Diego,

    I have myself updated the connectivity diagram between CODEC to McBSP lines. Please have a look on the snapshot given below and kindly verify if this is good to go. In our previous design we were connecting 24MHz but now changed to provide the SCKI to 24.576MHz from external oscillator.

    Please let me know if we need to change any connection on this.

    Looking forward for your kind reply.

    Kind regards,

    Muhammad Awais

  • Hello Diego,

    Please confirm the connections as per my last message so that we can go ahead to implement it.


    Thanks,

    Muhammad Awais
  • Hi, Muhammad,

    From the codec point of view, the diagram is correct. I am not really familiar with the McBSP interface but I assume the connection is correct for both master and slave. Having a common master clock (SCKI) for the processor and codecs is fine.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • Thanks Diego for your help. I am implementing it accordingly.

    Does TI also reviews the final schematics for CODEC?
  • Hi, Muhammad,

    I need to make a correction, I made a mistake on the diagram shared previously, I was using two devices where only one is required as the PCM3168A supports 6 ADCs. Please refer to below corrected diagram.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer