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DM6467 McASP0 output I2S mode problem

Tai Chang
Intellectual 740 points

Other Parts Discussed in Thread: TLV320AIC32

HI all,

I would like to make McASP0 output  BCLK: 3.072MHz, FS: 48KHz,

I need to adjust the divider of ACLKXCTL and AHCLKXCTL.

but it always output in most approach value ==> BCLK: 3.125MHz, FS: 46.xx KHz

Does anyone has the same problem?

 

Tai

  • 0
    Genius 4530 points

    Hi,

    Assuming that your divider value is set correctly...

    Have you checked that your AUX_CLKIN ,which is responsible for generating McASP0 clocks in master mode, is exactly 24 Mhz or it has some offset as well?

    If it has an offset as well, then the internal SYSCLK3 driving McASP0 and derived from PLL values will also change/ will have an offset.

    Regards,

    Sid

  • 0 in reply to Sid
    Intellectual 740 points

    Hi Sidharth ,

    I connect 24MHz on AUX_CLKIN  pin.

    divider is 8, so the BCLK is 24/8=3Mhz

    fs length=32, so FS rate is 3MHz/64(L+R)=46.875KHz !!!!

    Thanks,

     

    Tai

  • 0 in reply to Tai Chang
    Genius 4530 points

    Hi,

    In your first post, you have mentioned your Fs as 46.xx...

    Is it 46.875 as your calculations show?

    If yes then you may have to adjust your multiplier and divider values.

    Regards,

    Sid

  • 0 in reply to Sid
    Intellectual 740 points

    Hi Sidharth ,

    I do not see any multiplier in datasheet ..but only divider.

    24MHz/8(divider)/64(fs width)=46.875KHz.

     

    Thanks,

     

    Tai Chang

  • 0 in reply to Tai Chang
    Genius 4530 points

    Hi,

    Which codec are you using?

    A codec in DM6467 EVM by the name of TLV320 AIC32 can be used in both master and slave mode,

    If you want your BCLK and Fs(which can be equal to WCLK) as accurate as you mention above, then such accuracy can be obtained by using Codec as the master (i.e. McASP as the slave) so that codec generates the clock using MCLK.

    The codec has certain calculations which can help you calculate clocks having accuracy/resolution upto 3 decimal points by making some register settings.

    Hope this proves helpful.

    regards,

    Sidharth

     

  • 0 in reply to Sid
    Intellectual 740 points

    Hi,

    Our board has one i2s master(dm6467), two i2s slave(TLV320 AIC32  and idtv936 HDMI transmitter).

    In original settng, the TLV320 AIC32 as master, dm6467 as slave, idtv936 as slave, but there is no sound comming to HDMI to TV...

    So we now use dm6467 as master and got sound from HDMI, but there is a little bit noise !!!

    So I wonder that it is caused by the un-accurate FS ....

     

    Tai Chang

  • 0 in reply to Tai Chang
    Genius 4530 points

    Hi,

    As you suuggest, un-accurate Fs maybe the reason.

    Generally, audio codecs have an analog loopback facility. Execute it to make sure that the noise is not due to faulty resistors or leaky capacitors on board.

    If the sound quality is perfect, then un-accurate Fs will be the problem. But the divider values in McAP0 controller dont have enough resolution to achieve highly accurate Fs. This resolution can be obtained from TLV320AIC32 dividers.

    I suggest you stick to your original setting, and try to debug at the functionality level, this would ensure that your settings are correct and it is just the functionality that you have to recheck.


    regards,


    Sidharth

  • 0 in reply to Tai Chang
    Intellectual 995 points

    Hi,

    I have the same problem.The noise is not caused by the un-accrate FS ...But  ,now i do not know why

  • 0 in reply to jt huang
    Genius 4530 points

    Hi,

    Can you give some more details?

    Are you using the same audio codec-TLV320AIC32? Have you tested analog loopback?If the analog loopback is noisy, it means you have some leaky capacitors/hardware fault.

    Regards,

    Sid

  • 0 in reply to Sid
    Intellectual 995 points

    Hi,

    Yes .I  use codec-TLV320AIC32.I have tested analog loopback,but it is still noise.The noise is rustle. My board is   TI EVM.

  • 0 in reply to jt huang
    Genius 4530 points

    Hi,

    Some quick questions-

    1. Is the noise present in analog loopback mode?

    2. If the board you are using is TI's EVM, have you tried running the demo audio codes? Is there noise present while running those too?

    3. Are you using your own code? If TI's code doesnt generate noise, then there must be a slight problem in your code.Some more details about your application might help.

    Regards,

    Sid

  • 0 in reply to Sid
    Intellectual 995 points

    Hi sid,

     The noise is present in analog loopback mode.In analog loopback mode it donot need to run app code.My kenel code is simple to the TI code .

    Thanks.

     

     

  • 0 in reply to jt huang
    Genius 4530 points

    Hi,

    The noise in analog loopback mode suggests some hardware problem. My suggestions would be to use a CRO to trace the path of audio signal and check where the noise gets added.

    Possible reasons could be a leaky capacitor, a faulty inductor, or a wrong-value resistor (very unlikely).

    Also, if the noise has been added after the audio has been looped back, then the problem might lie in the IC or someplace else.

    Regards,

    Sid

  • 0 in reply to Sid
    Intellectual 995 points

    Hi,

       I set the DSP is master,and aic32 is slave.Setting fs is 8k,using IIS mode ,But playing  recoding file must use 16k sample rate.who can help me ?

    Thanks!

    regards ,

     hjt