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audio ringing/crosstalk

Question asked by Cronin.Dennis.001 on Jun 7, 2016
Latest reply on Jul 12, 2016 by Rogers.Michael
I posted on the eval forum but after further experiments trying here.

I'm using the STM32F746G Discovery.  I'm using the audio_loopback.c demo slightly modified to use line inputs instead of mics.  I get lots of crosstalk/echo/ringing when I set the audio gain at any usable level.

At first I thought maybe it was because of crosstalk between the input/output circuit board traces, but they are very short, and then I used an external low impedance buffer which should prevent crosstalk I would think.

I had to modify the BSP_AUDIO_IN_OUT_Init routine to allow an audio input type of  INPUT_DEVICE_INPUT_LINE_1 and code below suggested that would be handled even though the example disallowed that as an input.

The slight delta is it uses CODEC_AUDIOFRAME_SLOT_02 instead of CODEC_AUDIOFRAME_SLOT_13.  I don't have a conceptual understanding of what those slots mean.

It seems like what I'm trying to do should be fairly common: take an audio input from the line inputs and output it to the line/headphone outputs.

Pointers or suggestions?