Nano 33 IOT - Sketch Upload forces CPU Reset

Hi Community,

the brand-new Nano 33 IOT drives me nuts.
I can't upload anything without ending in a CPU Reset after compilation.

  • Correct Board loaded
  • Correct Port attached
  • Port is working correctly - see Board Info (attached)
  • Sketch is empty - no compilation errors
  • Upload start as usual, takes its time, no errors


then the "thing" performs a CPU Reset (see CPU Reset message). Every time when a upload is initiated.

I have a few Arduinos but this one hate me.

Appreciate any help. Thanks.

(mod edit)

Nano 33 IOT - Board Info.jpg

Nano 33 IOT - Board Info.jpg

Looks normal to me.

CPU reset message is not an error. When you upload your sketch, it reset the board so that it can start running your sketch.

The reset ensures your Arduino is in a known state by setting most registers including program counter and stack pointer to a fixed value (a few are only reset by power on).

This is done on older Arduino's as well, but you likely do not notice this. Because the new Arduino's handle their Serial communication through their on-chip USB peripheral there will be a side effect (USB reset and short COM connection loss). On the older Arduino boards the USB connection is handled by a separate chip so there is not disconnect.