Integrating INMP621 pdm microphone with MS12SF1

[Rakshita]

I am using a ble+wifi module which is MS12SF1 which has nrf5340+nrf7002. It is connected with a pcb in which there are 2 inmp621 pdm microphones. I have tried integrating it but not getting correct results. The clock and data are coming fine when seen through the oscilloscope. I am attaching my code below for reference and also the data which I was getting.

inmp621_mic.zip
[00:00:03.886,901] <inf> mic: RMS value in dB is: -1108220482
[00:00:03.891,967] <inf> mic: RMS value in dB is: -1108220482
[00:00:03.897,033] <inf> mic: RMS value in dB is: -1108220482
[00:00:03.902,130] <inf> mic: RMS value in dB is: -1108220482
[00:01:39.106,414] <inf> mic: RMS value in dB is: -1108220482
[00:01:39.107,452] <inf> mic: RMS value in dB is: -1108220482
[00:10:11.109,619] <inf> mic: RMS value in dB is: 617044095
[00:10:11.114,715] <inf> mic: RMS value in dB is: 617044095
[00:10:11.119,781] <inf> mic: RMS value in dB is: 617044095
[00:10:11.124,877] <inf> mic: RMS value in dB is: 617044095
[00:10:11.129,974] <inf> mic: RMS value in dB is: 617044095
[00:10:11.135,070] <inf> mic: RMS value in dB is: 617044095
[00:10:11.140,167] <inf> mic: RMS value in dB is: 617044095
[00:10:11.145,233] <inf> mic: RMS value in dB is: 617044095

[Amanda Hsieh]

Hello,

Most of the staff is away for a long weekend in Norway, so there will be some delays in response time. Thanks for your patience.

[Rakshita]

So I have been working on this for very long but the actual thing is that the pdm data which I am getting directly from the microphone looks like


00> [00:09:25.314,758] <inf> mic: PDM buffer data: -1
00>
00> [00:09:25.314,758] <inf> mic: PDM buffer data: -1
00>
00> [00:09:25.314,788] <inf> mic: PDM buffer data: -2
00>
00> [00:09:25.314,788] <inf> mic: PDM buffer data: -2
00>
00> [00:09:25.314,819] <inf> mic: PDM buffer data: -1
00>
00> [00:09:25.314,819] <inf> mic: PDM buffer data: -1
00>
00> [00:09:25.314,849] <inf> mic: PDM buffer data: -1
00>

And this data doesn't even changes after tapping on the microphone also

I had worked with the Thingy53's microphone which is also a PDM microphone, the difference between inmp621 and vm3011 microphones is that in vm3011 i2c is being used (maybe internally also and the pdm data which the microphone gets, it is getting sampled and filtered internally) and there is a possibility that the data which I am getting from inmp621 is not getting filtered or sampled but still when there is a sound the raw pdm data should be changing which it doesn't 

[JONATHAN LL]

Have a look at the steps discussed here:  https://devzone.nordicsemi.com/f/nordic-q-a/109455/how-to-use-device-tree-to-set-up-pdm-pin-configurations-with-nrfx-pdm-directly-no-dmic  

Regards,
Jonathan