Problem Input SPDIF in USB AUDIO XK216 MC APPLICATION

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happy noob
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Joined: Tue May 14, 2019 3:20 pm

Problem Input SPDIF in USB AUDIO XK216 MC APPLICATION

Post by happy noob »

Hello dear forum members and XMOS employees,

We have met a problem of SPDIF input in a example application.
We use the multichannel audio platform XK-AUDIO-216-MC-AB with the example application app_usb_aud_xk_216_mc. According to the buiding configuration chapter of "USB Audio Design Guide", we use the configuration 2i10o10xssxxx.
We understand that in this configuration SPDIF is on the channel 9 and 10, and there is no DAC analog output for them. So we did a very little change in the audio.xc file to have SPDIF on the DAC output:
/* Output "even" channel to DAC (i.e. left) */
for(int i = 0; i < I2S_CHANS_DAC; i+=I2S_CHANS_PER_FRAME)
{
//p_i2s_dac[index++] <: bitrev(samplesOut[frameCount +i]);
p_i2s_dac[index++] <: bitrev(samplesOut[frameCount +8]);
}

So in this change, we have copied the SPDIF signals to all "even" I2S input of the DAC module, logically we will have the SPDIF analog result on all "even" DAC analog output. But the reality is that we have nothing on those output. We have maked sure that SPDIF input runs very well with the AN00231 example code.

So the question is: Did we do anything wrong? If our method is wrong, then how can we have the SPDIF analog on the DAC output?
Hope someone can help, and thanks in advance!


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