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PCM1681: hardware mode in TDM

LOIC MARCHET
Prodigy 70 points
Part Number: PCM1681

Hello,

Do you have a recommended schematic using a PCM 1681 in hardware mode with a TDM signal without masterclock?

  • 0
    TI__Guru 53503 points

    Hi Loic,

    If you are using TDM, then your BCK is usually BCK = 256×fS, so you can connect the BCK to the SCK as the master clock.  

    You will need to configure the device hardware mode:

    And select the FMT as TDM.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 70 points

    Hi Paul,

    I was doing theses settings and no sound.

    My TDM format is :

    Format: TDM8 (BCLK = 8*32*FS)

    Sampling Frequency: 48000

    TDM voltage : 3,3V

    I put DATA 2/3/4 to GND (or not connected) : no sound. What you recommand for theses inputs in TDM mode ?

    My configuration is :

    FMT0/ FMT1 to 3,3V

    MUTE to 0V

    DEMP to 0V

    MSEL to 3,3V via a 220K resistor

    SCK same as BCK

    BCK / DATA 1 / DATA 2 / DATA 3/ DATA 4/ LRCK / SCK connected via 47 ohm resistor

    Did I miss somethink ?

    Best regards

  • 0 in reply to LOIC MARCHET
    TI__Guru 53503 points

    Hi Loic,

    This looks correct to me.  Let's verify the essentials:

    Can you confirm that the VCC voltages are all present (and ~5V)?

    Can you verify the voltage on the VCOM pins? should be ~2.5V.

    Can you confirm the data from the I2S source is valid? Best to look at it with an oscilloscope or logic analyzer.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 70 points

    Hi Paul,

    By doing a lot of checking, I finally found my error.

    When writing the signals to the PCB, I reversed the order of the pins on the input connector.

    Now it works fine in TDM.

    I then tried in I2S format by setting FMT1 to a low level and it does not work.

    Maybe my I2S format is not compatible with the hardware mode.

    It's not a problem, I planned to use TDM.

    Thanks a lot Paul.