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ADAU1467 TDM512 issues

Category: Datasheet/Specs
Product Number: ADAU1467

Hello,

I am using an AKM AK5538 ADC in TDM512 mode (schematic attached). The DSP settings for Serial In 0 are also attached.

BCLKO0, LRCLK0 are outputs into the ADCs BCLK and LRCLK. MCLKO goes to ADC MCLK.
SDTO goes to SDATAIN0.

Unfortunately when attaching 8 level meters to the 8 inputs, I only see activity on channel 1 and 2.

Parents
  • Now I am a step further - it was the output serial port setting (wrong clock ratio due to wrong amount of channels).

    But now, the Meters are reading -34dB when no signal is attached, but I can see audio.

  • The sample rate is 48kHz. I am actually just using one board currently, but might be using 2 chined according to the left configuration on the block schematic.

    Now I see activity on all 8 channels if I connect audio input, but the inputs never go to 0. They stay at -34dB when nothing is connected.

    TDMTEST.dspproj

  • Hello Sylwester,

    Your project is working fine for me, I tried giving TDM16 inputs. please look below.

                     when input is given                                                                when no input is given

             

    I see that you set the serial input port as TDM16 and you made the DSP master, so the BCLK going to the ADC will be 24.576MHz, this clock (512*fs) is for TDM512 mode (which is a chained mode) but now you are only using TDM8 Out from the ADC (TDM256 mode in your ADC). Since you are using 8 channels out from ADC, you just try running your ADC in TDM256 mode (TDM8 out which is 256*fs = 12.288MHz BCLK), to do that just set the serial input port as TDM8 (8 channels,32 bit per channel), it will generate 12.288MHz BCLK and send that to your ADC. Then it will be running at TDM8 mode.

    They stay at -34dB when nothing is connected.

    you disconnected the audio cable from the board, and it still shows -34dB? or did you stop playing the audio with the cable being connected?

    but the inputs never go to 0

    when no input is there, the meters will not go to 0 (which is a full-scale value - 0dBFS is full level), rather it goes down like around -80dB etc..

    Did you probe the ADC out signals to see what it's sending? 

    Regards,

    Harish

  • I think I am stuck with TDM512 mode, because I am using the "hardware / parallel" config mode of the ADC and
    according to the configuration table it is now fixed at TDM512, auto detect samplerate mode (all clocks slave).

    If I disconnect the cable, the outputs stay at -34dB.

    Is there maybe a sigmadsp project you can send me to test in case I went wrong somewhere?

    Regards,
    Syl

  • I am unfortunately unable to make any progress so far. Is there anything I can still check for TDM512 mode (even if the first / last 8ch input is set to GND (so all channels will be empty)?

  • Hello Sylwester,

    Sorry for the delay.

    So now, you can get all 8 channels from ADC into the DSP without a problem, the only concern you have is that when you disconnect the inputs, the meter reads -34dB. Is that right?

    can you send us the picture of your setup?

    Regards,

    Harish

  • Hello,

    I am not entirely sure if I am getting the channels correctly - my only test is currently with the VU meters, but cannot say if the data is correct or not, as I don't have a DAC attached (yet).

Reply Children
  • Hello Sylwester,

    Every ADC has a DC offset that varies part to part and over temperatures. 

    Most ADCs have a built in High Pass filter. Turn that on and this will fix this -34dB issue with the meters. 

    If the ADC does not have a HPF then use the DC block filter in the library. It is under the Miscellaneous filters in the Tree Toolbox. 

    Dave T