Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

JONATHAN LL — Wed, 23 Apr 2025 05:55:52 GMT

This is a old sample based on old code that did not use Zephyr, so it does not work. Only conceptually will be an example. It would need to be adapted to Zephyr so major changes.

There are other things in Zephyr to work with that might also be helpfull, https://docs.zephyrproject.org/apidoc/latest/group__audio__dmic__interface.html .

But we dont have a ready to use example.

Regards,
Jonathan

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Sun, 20 Apr 2025 13:23:58 GMT

Example https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/pdm-example-on-the-nrf52832 doesn't seem to be a complete document. It lacks files such as CMake and prj.conf.

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Sun, 20 Apr 2025 12:49:24 GMT

Do you have a try to extract the data from the code in the samples/drivers/audio/ dmic ?
And do you know other PDM acquisition programs of digital microphone using Nordic Zephyr? This is part of one of our engineering project.

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

JONATHAN LL — Thu, 17 Apr 2025 23:14:47 GMT

The supported freq is 16kHz.

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/pdm.html

https://docs.nordicsemi.com/bundle/errata_nRF52840_EngA/page/ERR/nRF52840/EngineeringA/latest/anomaly_840_128.html

The sample does not process or receive audio as noted in the description
https://docs.nordicsemi.com/bundle/ncs-2.9.1/page/zephyr/samples/drivers/audio/dmic/README.html

Could be an idea to look in the the Audio SDK for solutions.

Or there is this old nRF5 SDK example https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/pdm-example-on-the-nrf52832 that might work for some inspiration but dont think its to relevant as its not based on the same tools\driver implementation.

The AUDIO SDK might be something to look at but its designed for the nRF53.

Regards,
Jonathan

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Mon, 14 Apr 2025 14:01:11 GMT

I haven't found a solution. If you have any clue about my question? I have joined the Discord and posted my question.

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

JONATHAN LL — Mon, 14 Apr 2025 13:03:05 GMT

Hello,

Did you find a solution or are you still facing same issue?

I would also advice you to check with the Zephyr support Discord for help on this issue as they also have lots of people that have Here: https://discord.com/invite/Ck7jw53nU2

Regards,
Jonathan

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Sat, 05 Apr 2025 04:58:52 GMT

In dmic_nrfx_pdm.c, the clock frequency seems to be limited

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Sat, 05 Apr 2025 04:53:26 GMT

RE: Need Help with nRF52840 PDM Microphone Data Processing (Zephyr DMIC Example)

Lappland — Sat, 05 Apr 2025 04:52:58 GMT

This is the clock signal of PCLK32M_HFXO (blue) as the signal source collected by me with the oscilloscope, and the signal of the microphone (yellow).