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LADC/RDAC singnal impact

hakeen
Intellectual 740 points
Other Parts Discussed in Thread: OMAP-L137, TMDSOSKL137

Hi,

I'm developing on OMAP-L137 EVM. 

I could run the "sample program". All work normally.

Sample Program : Forwarding Line In sound to play at Line Out work normally. (Left and right work correctly)

I found some noise issue in DAC.  

My configuration:  

Only plug speaker in Line Out port.  

Don't plug anything in Line In port.

Program A:

1. write sin_wave into Left DAC.

2. read the value of Right ADC.  Write that value to Right DAC.

I could hear the clear and right sin_wave in Left Speaker (through LDAC).

I also hear some weak sound in Right Speaker (through RDAC). That weak sound is the replication of above sin_wave.

It seems Right ADC was impact by Left DAC....

Could someone give me some hint to debug?   Thx!

  • 0
    TI__Guru** 116100 points

    Hi Hakeen,

    I could run the "sample program". All work normally.

    Sample Program : Forwarding Line In sound to play at Line Out work normally. (Left and right work correctly)

    Where did you download the source file ?

    Is from Ti source or 3rd party or own ?

  • 0
    TI__Mastermind 35645 points

    Hi,

    Thanks for your post.

    How you are feeding left samples to left ADC? I mean, in what context, you are writing sine wave samples to left DAC?

    You should also ensure to configure the appropriate codec registers for left and right DAC's speakers used in the code through referring the corresponding codec data manual.

    To my knowledge, if you are not feeding any Line IN audio to left and right ADC, then you have to feed the sine wave samples simulataneously to left and right ADC's as inputs, process and appropriately write the sine wave samples to left and right DAC's to hear line out audio.

    Are you using TI evm boards or any custom board?

    Is it TI provided code or any custom code?

    Kindly recheck the appropriate codec registers configured for left & right ADC and DAC's used in the code.

    Thanks & regards,
    Sivaraj K

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  • 0 in reply to Sivaraj Kuppuraj
    Intellectual 740 points

    OMAP-L137 EVM is TI EVM

    http://www.ti.com/tool/tmdsoskl137

    It was produced by Spectrum.

    The sample code could be downloaded from spectrum.

    http://support.spectrumdigital.com/boards/evmomapl137/revg/

    I just utilized those sample code's register setting.