Flat waveform recording from nano 33 ble sense

I am successfully able to record two or three 10 or 22 second audio samples in a row from the built-in microphone. After that following the same process again, seemingly without any indication of an error from the daemon, a flat waveform is saved.

The current stopgap measure is to stop the daemon, reset the board, and restart the daemon. I’m trying to determine whether the issue lies in the board, a networking fault, my usb cable, or something else.

Any help is appreciated!

Hello @datameta,

Do you have the same issue when using the WebUSB feature?

My suggestion would be to try first with a different usb cable. I don’t think it comes from a network issues but it might be worth trying on another network too.

If none of the above solutions work can you try reuploading the edge impulse firmware onto the nano 33 ble sense?


Hmm, definitely seems to be device related, as the signature matches (which is calculated on device).

edit: I’ve done 5x 22 second samples on the Nano 33 BLE Sense using the latest firmware and daemon v1.13.14 and that works well.

I used a different usb cable, reflashed the board, and it looks like I had to update packages with arduino-cli. However I was only able to get 3x 22s samples before a flat waveform.

But, then I noticed on the dashboard Latency Calculations was set to (default?) Cortex-M4F 80MHz which I changed to Cortex-M4F 64MHz. Following that I successfully got 6x 22s samples!

Thank you both for your input!


Ah, it looks like that didn’t fix it fully. Got a failure on the third sample attempt this time. Where can I find the WebUSB tool? Perhaps that is the one thing left to try.

Hello @datameta

You can find it under the data acquisition view on the upper right corner.
Note that there was a recent issue with WebUSB tool, see Browser Crash When Using WebUSB and Nano33 for more insights.



I have so far incrementally tried the following

  • New Nano 33 BLE Sense w/ fresh firmware flash
  • New USB Cable
  • Different USB port

And I still ran into the flat waveform issue 3-6 samplings in.
Looks like WebUSB doesn’t have that issue! However using WebUSB I have run into what is potentially a bug? Sampling failed: Timeout when waiting

@datameta Are you using the firmware from https://docs.edgeimpulse.com/docs/arduino-nano-33-ble-sense or one that you built from the Studio?

@janjongboom I’m using the firmware from that link.

Edit: I did some testing with shorter samples and it looks like it may not actually be a flat waveform. Here is a 2s audio sample in the failure mode:

Thanks @datameta I’ve created a ticket for the embedded team to investigate.

Thanks @janjongboom.

So far I’m otherwise rather happy with my experience using Edge Impulse!

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Hi @datameta,

It’s been a while. Are you still experiencing issues with recording audio on the Arduino Nano BLE 33? I tried to reproduce, but for me it works fine.

Hello… I think i’m having the same issue with Nano 33 ble sense! It was working fine few days back…
However, i checked uploading the PDM Serial Plotter code to the arduino. Apparently it can hear tones and is generating the waves… (i used tone generator app).

What to do next? I have tried updating the edge impulse firmware… have tried re flashing it. Nothing works…