XMOS xCORE-200 Multi-channel Audio board Design Manual page 32

USB Audio Design Guide
The main requirements of this control are to
Set the mapping of input channels into the mixer
Set the coefficients for each mixer output of each input
Set the mapping for physical outputs which can either come directly from the
inputs or via the mixer.
There is enough flexibility within this configuration that there will often be multiple
ways of creating the required solution.
Whilst using the XMOS Host control example application, consider setting the mixer
to perform a loop-back from analogue inputs 1 and 2 to analogue outputs 1 and 2.
First consider the inputs to the mixer:
./ xmos_mixer -- display - aud - channel - map 0
displays which channels are mapped to which mixer inputs:
./ xmos_mixer -- display - aud - channel - map - sources 0
displays which channels could possibly be mapped to mixer inputs. Notice that
analogue inputs 1 and 2 are on mixer inputs 10 and 11.
Now examine the audio output mapping:
./ xmos_mixer -- display - aud - channel - map 0
displays which channels are mapped to which outputs. By default all of these
bypass the mixer. We can also see what all the possible mappings are:
./ xmos_mixer -- display - aud - channel - map - sources 0
So now map the first two mixer outputs to physical outputs 1 and 2:
./ xmos_mixer -- set - aud - channel - map 0 26
./ xmos_mixer -- set - aud - channel - map 1 27
You can confirm the effect of this by re-checking the map:
./ xmos_mixer -- display - aud - channel - map 0
This now makes analogue outputs 1 and 2 come from the mixer, rather than
directly from USB. However the mixer is still mapped to pass the USB channels
through to the outputs, so there will still be no functional change yet.
The mixer nodes need to be individually set. They can be displayed with:
XM0088546.1
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