How to sample MEMS microphone pcm data with NUCLEO-H743ZI2?

[Siyou]

Hi ST experts,

I tried to read out MIC( Infineon-IM69D120) data with NUCLEO-H743ZI2 SAI PDM interface as below but no lucky, the expected audio freq is 16KHz, attached are the src code and pcm data log  in a quiet environment, could you help to check why the data was not close to zero?

besides, the snapshot in AN5027 Rev2 is not match with STM32CubeMX V6.2.1 and V6.2.0, can you share the version of STM32CubeMX which AN5027 based?

[Siyou]

anyone can look into it and share comments?

[Siyou]

I changed the mic to MP34DT01, it still cannot work.

here is the output and interface waveform, could you help to check whether it is correct?

[Siyou]

Two more questions：

1, The PDM clock seems could not be modified to 2.048MHz? No matter what the PLL2.PLL2N was, whether it was 128 or 256, the PDM clock always was 1.024MHz.

2, in example <Projects\STM32H743I-EVAL\Examples\SAI\SAI_AudioPlayback\Src\main.c>

why the SAI input was LSB but the PDM filter was set to MSB?

SaiInputHandle.Init.FirstBit            = SAI_FIRSTBIT_LSB;
 
PDM_FilterHandler[index].bit_order  = PDM_FILTER_BIT_ORDER_MSB;