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TLV320AIC3111EVM-K: I2S DOUT pin is giving output data even if there is no audio input

Part Number: TLV320AIC3111EVM-K
Other Parts Discussed in Thread: TLV320AIC3111


I am using TLV320AIC3111 EVM-K audio CODEC as slave and providing MCLK, BCLK, WCLK from microcontroller act as master. Audio CODEC using line in as input and I2S as output. I am able get data over I2S Dout pin but there is one issue, even if there is no audio input , still I am getting invalid data on I2S DOUT pin, I checked this using oscilloscope.

My requirement is as follows.

What is reason behind this and How to stop this invalid data?

  • Suvarna, 

    The reason behind this is that your ADC is still converting regardless of whether you provide input or not.  so what you see is the noise floor being transmitted. If you want the DOUT to stop transmitting data, then Turn off the ADC. 

    best regards,

    -STeve Wilson

  • Hi Steve,

    Thank you for your reply.

    I am transferring the I2S data to controller and from there it is transferred over BLE. On mobile app, I am receiving the audio data and I am getting issue of crackling noise whether or not there is audio input. On the headphone line of CODEC ,I am not getting this problem.

    According to your suggestion I disable the ADC after that crackling noise is gone but the CODEC not able to send audio data on any peripheral.

    What is the issue for this crackling noise.

    I have attached the screenshots of the waveform of the I2S_DOUT pin for the case of without Audio input

  • Suvarna, 

    There isn't a crackling noise when idle when I listen to the AIC3111.  can you give more information?

    What do you have connected to the input of the ADC?  

    best regards,

    -Steve Wilson

  • Hi Steve Wilson

    I am using external microphone through line in input of  3.5 mm audio jack of the codec as the input to ADC.

    Giving output to headphone and to external microcontroller using I2S peripheral.

    As I told on headphone side I don't have crackling noise issue, but on BLE side I am getting this issue and if disconnect the DOUT pin of I2S this crackling noise is gone.

    Input and output audio frequency is 8khz

    fclk:- 8KHz

    mclk:- 2.048Mhz

  • Suvarna, 

    Disconnecting the DOUT does not necessarily mean that the crackling noise comes from the Codec.  only that the noise is illuminated when communications cease. 

    It could be a formatting issue perhaps the BLE processor is does not have an identical Audio Bus setup to the Codec?  

    You could test this by shorting DOUT to DIN,  and if you don't have crackling sound then your issue isn't the codec itself. 

    best regards,

    -Steve wilson