STM324xG_EVAL microphone (MP45DT02) problem

Posted on July 11, 2015 at 06:36

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.