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STM324xG_EVAL microphone (MP45DT02) problem

Question asked by rizzo.adriana on Jul 11, 2015

I want to use ST MEMS microphone (MP45DT02) on STM324xG_EVAL board, I used an extension board and attached the digital microphone to the board. It works very well when I use 16 KHz for AudioFreq, I mean:

#define DEFAULT_AUDIO_IN_FREQ                 I2S_AUDIOFREQ_16K

But I want to have 8 KHz frequency for my final audio output and when I use I2S_AUDIOFREQ_8K in my code, the Input clock frequency for microphone become about 500 KHz and so because of  microphone ‘s Input clock frequency characteristic (1-3.25MHz),it doesn’t work.

How can I have 8 KHz for my final audio output?

The wondering matter is that Discovery Board works with 500 KHz for microphone ‘s Input clock frequency and I know the frequency of the PDM data output from the microphone (which is the clock input to the
microphone) must be a multiple of the final audio output needed from the system.

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