nRFx PDM driver data buffer handling gives noise samples at every memory block of defined size

RE: nRFx PDM driver data buffer handling gives noise samples at every memory block of defined size

Simonr — Thu, 08 Oct 2020 08:04:43 GMT

Hi again

You can also check out the Smart Remote 3 DK add-on that has a digital microphone that can do something like this. The firmware can be downloaded here. I'm not too familiar with it, but there should be some noise mitigation code here as well. Alternatively, you might be able to use the buffer handler in the Thingy SDK as reference to see how it's done there and implement something similar in your project.

Best regards,

Simon

RE: nRFx PDM driver data buffer handling gives noise samples at every memory block of defined size

ShalinDoshi — Wed, 07 Oct 2020 11:27:01 GMT

Hi Simonr,

we are using nordic SDK 17 with soft device version s140 for the devkit nRF52840. I saw the code you are pointing out for reference but those APIs will not be used in above SDK and would not be compatible with nRF 52840.

Is there any other method which might help me to mitigate some noise?

RE: nRFx PDM driver data buffer handling gives noise samples at every memory block of defined size

Simonr — Tue, 06 Oct 2020 12:18:01 GMT

May I suggest taking a look at the Thingy:52 SDK (downloadable here). The Thingy uses a digital PDM microphone, and a part of this SDK is PDM audio drivers with audio codecs. Specifically, take a look at how the buffer handling is done in the Thingy SDK. The m_audio_buffer_handler() and m_audio_process() functions in drv_mic.c should be helpful.

Best regards,

Simon