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Noise in EZDSP board with AIC3204

Omkar
Prodigy 140 points

Hi All,

    I am working on EZDSP 5515 board which is having AIC3204 codec. I am  running the "aic3204_loop_stereo_in1" program in "aic3204" test which will take the stereo input and loopback it to headphone. When I increase the ADC volume (page 0, register 83, 84 of aic3204) , I observe noise in the headset even when the linein1(stereo in1) is open. And the noise is increasing with the volume. Why it is so? Can anybody help me in removing the noise please.

 

Thanks and regards,

Omkar.

 

  • 0
    TI__Intellectual 1035 points

    Hello Omkar,

    When you mentioned that you hear the noise when the line-in is open, did you mean that it is physically disconnected, or that there is no audio input being sent to the board although the cable is connected?

    Also are you connecting the Audio out of your laptop/PC that you are using to power up the board to the 'Line-in' of the EZdsp board? I have seen a similar issue in the past in such a scenario.  If so could you try connecting the 'Line-in' of the EZdsp to a separate device like an MP3 player? Let me know if you still hear the noise.

    If you still hear it, let me know what kind of noise you hear. Is it a static random noise or a repeating tone?

    Regards,

    Mugdha Gadkari

  • 0 in reply to Mugdha Gadkari
    Prodigy 140 points

    Hi Mugdha,

         The line-in is physically disconnected. The noise is random with small amplitude. I have done an experiment to capture the noise. I kept the ADC volume to zero. I took a buffer of length 48000 to capture the real time values. I am taking the values of "I2S0_W0_MSW_W" port into the buffer so it has given me the one secon real time values, as per the settings. I dumped the values to a file and plotted. It is showing that first few values are zero and suddenly it is jumping down to the negative amplitude of 127. There it is creating the random noise of amplitude span 5 i.e. -130 to -125. It is random in nature. This span is increasing with the ADC volume. Please let me know if you need more information about the issue.

     

     

    Thanks and regards,

    Omkar

  • 0 in reply to Omkar
    Prodigy 140 points

    The noise is there even when the line-in is connected with PC and nothing being sent.

     

     

    Regards,

    Omkar.

  • 0 in reply to Omkar
    TI__Intellectual 1035 points

    Omkar,

    I'll look into it and get back to you.

    Regards,

    Mugdha Gadkari

  • 0 in reply to Mugdha Gadkari
    TI__Intellectual 1035 points

    Hi Omkar,

    I could replicate the issue on my side. I have been checking a few things internally. We still haven't narrowed it down to a specific problem but we are looking into it. I have received more details yesterday from one of the TI engineers you were in touch with. That's helpful. I will email your team directly with updates as requested by your engineer.

    Regards,

    Mugdha Gadkari

  • 0 in reply to Mugdha Gadkari
    Prodigy 140 points

    I think the issue is with AIC3204 codec. We have an AIC3254 USB EVM. We are observing same type of noise for higher volumes. We could not capture it but I think the same issue remains with lower volumes also.

     

     

    Thanks and regards,

    Omkar

  • 0 in reply to Omkar
    TI__Intellectual 1035 points

    Hello Omkar,

     

    Thanks for confirming this. After tests on our side we are also confident that it is not related to the C5515 DSP itself.  It would be great to if you could post the solution on the forum once you find it so others might be able to benefit as well. Another thing to keep in mind is that the Ezdsp board is a demo board to demonstrate and test the various capabilities of the DSP with multiple peripherals on the same board. It is in not intended to be a production quality layout. 

    We will also pass along this information to Spectrum Digital who is our partner for demo boards/demo code so they can try to improve it for future generations.

    Regards,

    Mugdha

  • 0 in reply to Mugdha Gadkari
    Prodigy 140 points

    Sorry to say that my previous conclusion was wrong. I rechecked all the things again. The codec noise is present only if you use  more than 24dB headphone driver gains(page 1, reg 16, reg 17). The noise is not there if I use maximum ADC volume or DAC volume in AIC3254 EVM but in ezdsp the noise is present in above 3 cases. We can easily differentiate the codec noise and the noise in ezdsp. The codec noise will start when you do the register settings and remains (even when the program is not running) until you change the register settings again, where as the noise in ezdsp will be audible only when you run the progarm. So the issue is more towards ezdsp. It will be very helpful if you are able to get continuous zero or dc value at the input side in the previous code that we sent to you. Please let me know if you need more details.

     

     

    Thanks and regards,

    Omkar

  • 0 in reply to Omkar
    TI__Intellectual 1035 points

    Hello Omkar, 

    Thanks for the update. We do not think that the problem is related to the C5515 DSP itself. Having said that, we think that it could be because of the board layout or codec related layout issue. We will pass along this information to Spectrum Digital which is our partner for demo boards and demo code so they can incorporate any findings to try and improve it for future generations.  

    The Ezdsp board is a demo board to demonstrate and test the various capabilities of the DSP with multiple peripherals on the same board. It is in not intended to be a production quality layout. For highly sensitive applications, we would encourage you  to develop a prototype board with the C5515 for your product until we understand what the noise issue is on the eZdsp.  

     Regards,

    Mugdha

  • 0 in reply to Mugdha Gadkari
    Prodigy 140 points

    Hi Mugda,

          Thanks for the replies. We will start developing the prototype board. Please let us know whenever you get any update from your team or spectrum digital on this issue.

     

     

    Regards,

    Omkar

  • 0 in reply to Omkar
    TI__Intellectual 1035 points

    Thanks for letting me know Omkar. 'Spectrum Digital'  would like to get in touch with you to get more understanding of the noise issue so they can resolve it. Please email them directly at support@spectrumdigital.com or by clicking on "Help Desk" on their home page http://www.spectrumdigital.com. 

    Regards,

    Mugdha Gadkari

  • 0 in reply to Mugdha Gadkari
    Prodigy 30 points

    Hello, 

    I was wondering how much is the noise that you observe and whether it appears no matter what. i am a beginner and while i run the aic3204 example, the output is noisy.

     

    Dionysia

  • 0 in reply to Omkar
    Prodigy 205 points

    v

    Hi There,

    I am using C5515 EVM. I am having trouble in getting audio samples into my program. I've verified my config with yours (as shown above),  all looks OK, but no audio. For the stereo In,  I am using J9/J12 inputs and external microphone is connected.

     Your help will be much appreciated.  

     

    Thanks,

    Krishna.

  • 0 in reply to krishna prasad3
    Prodigy 205 points

    Also, The amplitude of the Line In samples is very low (or close to noise floor) and they are not changing even in the presence of loud input speech at the microphone input.