RE: I2S to USB microphone received data is periodically garbage (nRF Connect SDK v2.6.1)

Malek Itani — Thu, 04 Jul 2024 19:14:01 GMT

Apologies for the oversight and thank you for your help.

I will refer to the DK that relays I2S samples to USB as DK1, and to the other one as DK2. I connect pins together with jumper cables. Specifically, I connect:

P0.26 on DK1 to P0.26 on DK2 (SCK to SCK)

P0.27 on DK1 to P0.27 on DK2 (LRCK to LRCK)

P1.08 on DK1 to P1.08 on DK2 (SDIN to SDOUT)

GND of DK1 to GND of DK2

Both DKs are powered over the microUSB connector at the short edge of the board. I connect my host PC to DK1 over the other microUSB connector as well to interface with the USB audio device.

I hope this helps. Let me know if you need any other information.

Edit: After reading a bit more, it might be related to the fact that the nRF52 can't provide an exact 48kHz sampling rate. In Zephyr, the default sampling rate for the USB Audio Device Class is 48kHz, but there should be a way to change it. Howver, I believe this functionality was added in v3.6, while nRF Connect SDK v2.6.1 uses Zephyr v3.5.

If I change the I2S sampling rate to a frequency that *can* be generated by the I2S module, like 8kHz, I don't observe these spikes anymore, though as expected recording happens 6 times slower (because the USB device thinks it's running at 48kHz, when really its providing samples at 8kHz).

Is my reasoning correct here? Are there any possible workarounds?

RE: I2S to USB microphone received data is periodically garbage (nRF Connect SDK v2.6.1)

Sigurd — Wed, 03 Jul 2024 22:47:22 GMT

Hi!

[quote user=""]I've attached the project files for both dev boards for reference.[/quote]

Could you add a explanation on how you connect the 2 DKs together?