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PCM1791A: Not possible to use I2C for control, and stereo, and external digital filter mode?

inojosh
Prodigy 120 points
Part Number: PCM1791A

When using I2C, if you enable external digital filter mode, the PCM1791A sets the MONO bit automatically.

I am guessing this is because the MUTE pin (which would be DATAR when external digital filter mode is enabled) is used as A1 for the I2C interface.

I would have that that A0/A1 were only latched on POR, and the MUTE pin could be used as DATAR after that.

Is this not the case? Do I really have to use SPI in order to be able to use external digital filter mode in stereo?

  • 0
    TI__Mastermind 23920 points

    Hi Inojosh,

    You should be able to use I2C with external filter. The external digital filter application mode is accessed by programming register 20  , that is set  DFTH = 1 ( external filter) & MONO = 0    Stereo mode  in I2C mode.

     the I2S signals should be connected according to the following: 

    LRCK (pin 1): WDCK as word clock input 

    BCK (pin 2): BCK as bit clock for audio data

    DATA (pin 3): DATAL as L-channel audio data input

    MUTE (pin 4): DATAR as R-channel audio data input

    The word clock (WDCK) signals must be operated at 8× or 4× the desired sampling frequency, fS and it supports  right-justified audio format.

    Let me know if you have any questions.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 120 points

    When I write 0x10 to register 20, and then read that register, it comes back as 0x18.

    It looks like MONO is forced, since MUTE pin is AD1 when the interface is I2C.

  • 0 in reply to inojosh
    TI__Mastermind 23920 points

    What do you mean by "MUTE pin is AD1 when the interface is I2C."

  • 0 in reply to Arash Loloee
    Prodigy 120 points

    See datasheet, page 22.
    In I2C mode, MUTE is ADR1.
    This is apparently preventing it from being DATAR for external digital filter mode.
    That is, the MUTE pin is not just used to latch ADR1 on reset, it is taken to be ADR1 "forever" when in I2C mode.
    I just want some confirmation that it is not possible to use external digital filter mode (in stereo) and I2C mode at the same time, forcing the use of SPI.

  • 0 in reply to inojosh
    TI__Mastermind 23920 points

    ok, you meant ADR1  . As far as I know, you can use it in I2C as well, I believe once you write into  it,  it should be now used for MUTE or DATAR signals and reading it can give you a bogus  reading as it is not the same slave address. 

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 120 points

    I don't think this is the case. I continue to hold MUTE low, and the output is mono.
    If the MUTE pin really did properly become DATAR, then I would have one channel with audio, and the other without (since MUTE is held low).
    But both channels have identical audio, and reading register 20 shows MONO bit set.

  • 0 in reply to inojosh
    TI__Mastermind 23920 points

     I don't have an EVM to confirm your observation ,  datasheet doesn't indicate that. If I find any further information, I will updated this post.

    Regards,

    Arash