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TLV320AIC3120: Digital mic throughput

Reg Webb
Prodigy 65 points
Part Number: TLV320AIC3120


I have been tryint to use a digital mic with this part.  The PLL is working and has a clock of the correct frequency of 3.072MHz at GPIO1 output.  DIN is supposedly set as Data Input for the mic.  The clock is present and the data can be seen coming back from the mic but am unable to get the audio from the mic to the headphone output.  I have been working on this for several days and cannot see what I am doing wrong.  Is there an example program/script that show exactly how to do this or is there an order that things have to be setup and turned on.

Any help would be appreciated.

Thankyou

Reg

  • 0
    TI__Guru** 110815 points

    Hi Reg,

    The digital mic data is sent back to digital interface after ADC, as you can see from this capture the DMIC data is not accessible at the DAC output mixer:

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 65 points

    Hi Ivan,

    Thankyou for your reply.  I had thought that connecting ADC->DAC loopback (P0 R29) would have connected from the ADC to the DAC, is that not the case?  If that is not the case would I then have to take data out to the MCU via I2S from the ADC then back in to the DAC, would that work?

    Again thankyou for your help Ivan

    Reg

  • 0 in reply to Reg Webb
    TI__Guru** 110815 points

    Reg,

    Let me double check, but I don't think this loopback would work for DMIC data. My understanding is Mono ADC and DMIC data are two separate paths that are common only after the filter.

    You're correct, you would have to take the DMIC data from SDOUT and loop it back to SDIN from the host MCU.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Prodigy 65 points

    Ivan,

    Doing some more work on this is looks like if the loopback will not work as I was hoping that is would then one cannot use this device to collect audio from the digital mic and replay it through headphone/loudspeaker at the same time.  It looks to me as though it is not possible, since the DIN pin and GPIO pin are used for the digital mic there is no way to get data in and out of the device (I2S etc) at the same time.

    Is that correct?

    Thankyou for your help with this Ivan.

    Reg

  • 0 in reply to Reg Webb
    TI__Genius 13610 points

    Hey Reg,

    You may be able to still do this, have you tried making sure the mono DAC output is configured to receive L data?

    The Digital Mic input should be going into the L data line which would allow it to reach the DAC and the speakers, with no external or internal loopback involved

    Best,

    Carson

  • 0 in reply to Carson Allen
    Prodigy 65 points

    Hi Carson,

    Thankyou for gettting back to me with this information.  I will try that out when the dust settles.  Actually ended up solving it by using an STM32F405... to get the PDM from the mic and convert it to PCM then send to the 3120 by I2S, which works perfectly.

    Take care

    Reg