NRF5340 with PDM

[Mr.NCK]

HI,

 We are using the IM69D120 PDM mic for our audio application. I am able to interface the MIC and record audio with the NRF5340. 

       I have read the PDM data and stored it in an external SRAM connected through SPI. Then I read the data from SRAM and transferred it through BLE and captured the data with the help of the python app.

1) Test Case 1:  PIN mapping.

      At first, I connected the SRAM Pin to port 0 pins. I can get clear audio. But, I changed the SRAM pins to port 1 I can't be able to get the clear audio. The output audio has a clipping sound randomly.

      1) why is the audio coming correctly with port 0 pins alone? why it is not coming with port 1 pins? 

       2) Is there any configurations there to make it work with port 1 pins?

  2) Test Case 2: Zephyr timer and thread.

          Once I started using timer and thread in the same project. Again, I am not getting the non-quality audio.

           1) I need to know if this is because of zephyr. Because I have read the zephyr documentation (https://docs.zephyrproject.org/2.6.0/boards/arm/nrf5340dk_nrf5340/doc/index.html)

                in this documentation, the PDM is not listed in the zephyr supported hardware features list. 

Thanks & Regards

Navin

[Kenneth]

1) There is no reason I can think of that should cause this. Are you sure the only change you did was the pin mapping and no other changes was performed?

2) Maybe look at the PDM buffer and try to increase it? Sounds to me that the other thread/timer delay the PDM handling, so you may need to look into buffer size and priority of the PDM handling.

Best regards,
Kenneth

[Mr.NCK]

Hi Kenneth,

 Thanks for your response. 

1) I am sure there are no other changes performed.

2) PDM  and timer will run parallelly.Because based on the timer action we need to read one interrupt.

Thanks & Regards

Navin

[Kenneth]

I suggest to continue debugging and try "things", e.g. does it affect all pins on P1 or only some? Have you tried to change priority of threads and timers and pdm?

Kenneth

[Mr.NCK]

Hi kenneth,

Audio will affect with all pins on p1 and only one thread is assigned because of timer. So, that has higher priority 

Thanks & regards

Navin 

[Kenneth]

What is the markings on the nRF5340 IC you are using? I just want to ensure you are not using some early engineering sampels. 

Are you using the nRF5340DK for this test? If yes, what is the version of the DK?

Kenneth