Fuse error with Arduino UNO WiFi Rev 2

When uploading a sketch to the relatively new Arduino UNO WiFi Rev 2, there is fuse error generated.

Does anyone know how to eliminate that error?

Sketch uses 2634 bytes (5%) of program storage space. Maximum is 48640 bytes. Global variables use 175 bytes (2%) of dynamic memory, leaving 5969 bytes for local variables. Maximum is 6144 bytes. avrdude: WARNING: invalid value for unused bits in fuse "fuse5", should be set to 1 according to datasheet This behaviour is deprecated and will result in an error in future version You probably want to use 0xcd instead of 0xc9 (double check with your datasheet first).

void setup() 
{
  Serial.begin(115200);
}

void loop() 
{
Serial.println("Hello World");

}

It’s just a “warning” and you can ignore it.

Yes, I agree it is a warning and it does not affect the loading and running of sketches.

However, the Warning states that in the future, it will be an error. I would like to get rid of that warning now. Is it possible to reprogram the fuses? If so, how?

the Warning states that in the future, it will be an error.

Yeah, but … I think it’s more likely that the datasheet will change. ATmega4809 fuses are quite different than ATmega328 fuses, and the relevant line in the datasheet doesn’t make a lot of sense.

Hmm. In fact:

(2018) DS40002015A-page 28: “Note: When writing the fuses write all reserved bits to ‘1’.”

(2019) DS40002015C-page 31: “Note: When writing the fuses, all reserved bits must be written to ‘0’.”

In this version of the manual there is no note regarding reserved bits on page 31. Only page 28 has a note and that one says to set reserved bits to 1.

Looks to me like the document was updated.

https://www.e-lab.de/downloads/DOCs/Mega-0-Serie.pdf

Yep; that’s the “A” version. Go Microchip.com directly for the latest.
http://ww1.microchip.com/downloads/en/DeviceDoc/megaAVR-0-series-Family-Data-Sheet-40002015C.pdf

It looks like the change was actually in Rev B:

Atmel/Microchip has had some really annoying documentation errors recently…

westfw: . . . Atmel/Microchip has had some really annoying documentation errors recently...

I guess that a lot of the problems come when the data sheets are "freshened up" with new fonts and other corporate identity features like logos etc. The work is handed out to office assistants and the engineers are no longer around to check the results. Once one or two have been painstakingly updated, the person doing it begins to have a memory of doing a similar table etc. in a previous data sheet and blindly does a cut and past exercise, oblivious to any subtle differences in the underlying product. The other irritating thing is the tendency, instead of saying straight that some feature does not work or is otherwise unusable, is to write reams of descriptions of its bizarre behaviour and useless side effects.

From the 'B' version posted above.

Note: When writing the fuses, all reserved bits must be written to ‘0’.

Can we now agree this is clarified and all reserved fuse bits must be written as 0?