ADSP-21369 SRC 11kHz cut-off

Hello,

I hope anyone could help me with some signal problems using the SRC-units of the ADSP-21369 (with the EZ-Lite kit).

The goal was to provide a flexible upsamling-rate by a PCG. After some testing where I directly connected the ADC on the board to the DACs with just the SRC in between, the signal got cut off at about 11kHz. This cut-off did not occur if the SRC was left out.

In this example, the output of the SRC was clocked with the same frequency (FSCLK 48kHz) as the input.

Is there any configuration I did not find out that has to be done for the SRC? (Initialisation method at end)

The input and output are 24-bit i2s from the AD1835.

I would be glad if you have any idea where to find the error, thanks.

Greetings

Sven

Update1: I'm sorry to say this, but my measurements were partly wrong. without the SRC, the signal is not cut-off completely but some sort of amplitude modulation occurs... the amplitude is modulated with about 1Hz and 0.2Hz. But still the maximum is only half of the "normal" amplitude and at 13 kHz no measurable signal remains.

This description is valid with the adc pins directly connected to the dac pins via the sru, no sports, srcs or whatever is interlinked.

I tested the code on a second board but the same error occured, therefore I think it has to be an error in the code but I still have no idea even where to look.

In the appendix I added the source of the AD1835 initialization routine

attachments.zip
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  • 0
    •  Analog Employees 
    on Jun 3, 2015 7:30 AM

    Hi Sven,

    Apologies for the late reply. The SRC in ADSP-21369 supports upto 192KHz sample rate.

    So if you connecting the ADC to the DAC through SRU with SRC in-between , ideally you can get till 192Khz sample rate.

    Can you share the complete project which replicates the issue on the EZ-Kit( including the AD1835 codec initialization) .

    Regards,

    Mahesh

Reply
  • 0
    •  Analog Employees 
    on Jun 3, 2015 7:30 AM

    Hi Sven,

    Apologies for the late reply. The SRC in ADSP-21369 supports upto 192KHz sample rate.

    So if you connecting the ADC to the DAC through SRU with SRC in-between , ideally you can get till 192Khz sample rate.

    Can you share the complete project which replicates the issue on the EZ-Kit( including the AD1835 codec initialization) .

    Regards,

    Mahesh

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