New mbed directory for Arduino nano 33 BLE Sense

Not so much a bug, but a note for anyone running into the “The filename or extension is too long” error with newer versions of Arduino on Windows.

It looks like Arduino has made some changes to the way the mbed boards are supported. The “mbed” directory is no longer used (old mbed libraries are marked as “deprecated” in the Boards Manager). The directory “mbed_nano” is used instead for things like the Arduino Nano 33 BLE Sense.

I just tried the following on Windows 10 and Arduino 1.8.13:

  1. Go to Tools > Board > Board Manager. Search for “nano 33 ble.” Remove all packages that support that board (you will likely notice one that says “deprecated”)
  2. Install the latest “Arduino Mbed OS Nano Boards” package. For me, this was version 2.1.0.
  3. Save platform.local.txt (found here: in C:\Users<USERNAME>\AppData\Local\Arduino15\packages\arduino\hardware\mbed_nano\2.1.0 (the version might be different, depending on the version installed in the Board Manager).

This allowed me to compile the Edge Impulse examples.

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@ShawnHymel Thanks, we’re aware of this and are hoping to upgrade to the latest Arduino cores in our docs and examples soon (issues with the way serial is now handled are blocking there). @Arjan is on top of ti.

@aurel Can you add this to the platform.local.txt section on the Arduino docs page?


I updated the docs page. Also, this issue has been fixed in the latest IDE v1.8.15.



Good to know, thanks! I’ll update to 1.8.15 and give it a shot.