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stereo recording with 2 MEMS mics using libPDMFilter

Question asked by daddi.matteo on Jan 18, 2016
Latest reply on Jan 19, 2016 by daddi.matteo
Hello everyone,
I have a STM32F4-Discovery board with an integrated MP45DT02 MEMS mic, and I've bought also anothere mic (an MP34DT01), I would like to record at the same time from the 2 mics.

I'm able to record in RAM and playback the audio from the integrated mic, to do so, I've edited the example application "Audio_playback_and_record" (http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00040802.pdf).

To decode the pdm bitstream I use the libPDMFilter distributed with the example (its header is "pdm_filter.h")...

The problem is that the only documentation I've found for that lib is this:
http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00040808.pdf

...But there are no hints on how to decode a stereo bitstream produced by 2 mics (the only thing that is said is that, in the bitstream, L/R channel's bytes must be interleaved)...

I've tried a lot of configuration of all parameters but I still can't get the desired result...
At the end I'm able to get one channel or the other for example:
L channel ok, silence on the right channel.
Or (switching the bytes) the opposite
...But I can't get both channel togheter.

How to get L/R with libPDMFilter?

Otherwise... Are there any serious documentation about that lib?

Thank you very much!

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