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PCM1864 I2S Input AND Output

Max Makhnyk
Prodigy 155 points
Other Parts Discussed in Thread: PCM1864

I am building a design that incorporates both Mic and Line level inputs, we also have an I2S input. We mix the inputs together with DSP and then spit it back out via I2s into another chip (like in the image below). After browsing the TI site, I found that the PCM1864 is capable of doing this. While building the circuit, I ran into an issue. I noticed that there is only 1 BCLK and 1 LRCLK. This is an issue since I need both an I2S input AND output.

Is it possible to use the same LRCLK and BCLK for both input and output? Or could I use one of the GPIO as LRCLK and another GPIO as BCLK?

  • 0
    TI__Mastermind 27910 points
    Hi Max,

    Yes you can use the same LRCK and BCK for both input and output.

    Justin
  • 0 in reply to Justin Bohr
    Prodigy 155 points

    Hello Justin,

    Thank you for responding. I would like more information regarding this situation.

    I have attached a picture showing exactly what I want to accomplish and how I believe it works. I need the I2S data in AND data out lines running at the same time. I am having a hard to understanding how the LRCK and BCK running at the same time. 

    From the image, are both devices allowed to use the LRCLK simultaneously? I'm treating SCKI as "master in" and BCK as "master out". I just would like more information on this. Thank you!

    -Max

  • 0 in reply to Max Makhnyk
    TI__Expert 8230 points

    Yes you can use both input and output at the same time and the input can be mixed into the output in the Digital Mixer. As for the clocking, both the input and output will need to be synchronous with BCK and LRCK, these can either be generated by the PCM186X or sent to the PCM186X. The PCM186X is fairly flexible on clocking requirements. It is possible to run the PCM186X off of just LRCK and BCK if they are generated by an external chip. Please note that LRCK should be the same direction as BCK.

  • 0 in reply to Fernando Lopez
    Prodigy 155 points

    Hello Fernando, 

    Thank you so much for your reply. I believe this is what you meant, correct? So even though I2S Communication is supposed to be a three line operation, it's possible to only use two like I am doing below?

    All the names are in reference to the Texas Instrument IC. 

  • 0 in reply to Max Makhnyk
    TI__Expert 8230 points

    Hello Max,

    Yes, that's correct.