How to fix Noise issues in PDM to PCM Conversion?

[AiROT]

Hey,

We are implementing digital microphone interfacing using ST's IMP34DT05TR microphones connected to the STM32G473VET6 microcontroller through the PDM interface, following guidelines from the application note AN5027, specifically Example 3.

The configuration includes:

1. SAI GPIO and Pin Configuration
2. SAI Parameter Settings
3. SAI DMA Settings

We have included screenshots of these configurations.

We are utilizing the PDM filter library "libPDMFilter_CM4F_GCC.a" for converting PDM to PCM. However, the output PCM data, when converted to a .wav file or played directly, results only in Noise.

Could you advise on what aspects to check or steps to troubleshoot this issue effectively? Any help or guidance would be greatly appreciated.

AiROT.

[PGump.1]

Hi,

Make sure the header in your WAV file is correct - sample rate, bit length, n channels, endiness...

I hope that helps.

Kind regards
Pedro

[Aziz4576]

The noise issue is likely due to a mismatch in the PDM clock, filter settings, or DMA configuration. Verify the PDM clock matches the microphone specs, ensure the PDM filter parameters (like decimation factor) are correct, and check the DMA buffer alignment. Also, confirm your SAI settings and .wav file format are properly configured for playback.