Nano 33 BLE Sense Serial Monitor Issue

I've got a new Ardino Nano 33 BLE Sense, it seems to be working.
Test codes like Blink etc. work fine. Only when I need the serial monitor a problem occurs.

The Serial Monitor remains empty. Even simple programs like "hello world" don't work.The baudrate is correct of course. If I want to change the baud rate the drop down menu freezes. The problem exists on several different PCs. The drivers are up to date. I use the latest IDE (WIN10) on all PCs. It doesn't matter if I use the win10 app or the program. It is also noticeable that as soon as I start the serial monitor the program and the monitor can't be closed anymore until I disconnect the microcontroller from the PC. A very weird problem I never had before.

Does anyone have a similar problem?

All users of the new board has the same problem.
See NANO 33 SENSE: COM mismatch with Serial Monitor - Nano 33 BLE Sense - Arduino Forum
There is a work-around.

No its not that problem!
It is not about the known port switch.
My serial monitor does freeze. The serial seems to work.
When I use while (!Serial); the Arduino responds, for example when I use a blink as a test
But no matter what I do the serial monitor stays blank and I can't close it anymore until I disconnect the board. As mentioned its not a PC problem I testet on different PCs.

Sorry - there is no better help. Please read the top topic of this forum: near all problems are COM-related.

That is what I did, before I asked. Thank you.

Tested the online editor. it's the same. The serial monitor stays clear. The board checks that there is a serial monitor (testet with while (!Serial)) but the serial monitor shows nothing even for the easy hello world example.

It seems there was an update to a library for the SENSE.
Not sure if it will help in any way but worth a try.

Win 7 Pro x64, and both CREATE and IDE 1.8.10 are working here fine for the SENSE in regards to the serial monitor.

Also please ensure you are installing the IDE’s to a local drive and NOT a ONEDRIVE or similar cloud / network drive. There are known problems with COMMS and those approaches.


I had to add a delay after the while(!serial) line to get hello world to work with an ordinary BLE. I suspect that the same will be true of the BLE sense.

Uploading the code to Nano 33 is similar to any other boards, but do note that the board has two COM ports. When you click on the upload button the Arduino IDE compiles the code and then resets the board automatically through software command, this will put the board in boot loader mode and upload your code. Because of this, once the upload is done you might notice that the Arduino IDE has automatically changed its COM port to a different number and you might want to change it back before you open your serial monitor.

The above is from a blog, and is exactly what is happening to my Nano 33 BLE. How can this problem be corrected as it is a manufactures error.


It is NOT an error and is covered in a lot of posts.
It is also covered in the STICKY posts you saw on the way in here.

The IDE knows about it and also knows what to do !

Again it is NOT an error.
Might I suggest you read up on the boards capabilities a little more.