Arduino Uno Wifi Rev 2 Error Message


In the past, I've used the following schematic to connect an Arduino/Genuino Uno to an AD9850, and it worked smoothly:

I tried replacing the Arduino Uno with an Arduino UNO Wifi Rev 2, following the exact connections from the schematic above, and I get the following error message when it tries to compile:

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).

What does this mean, and how could I correct this?


That refers to unused bits in one of the Fuse bytes. It reads back unused bits as 1, while the boards.txt file as 0 in those bit positions.
0xcd = 11001101
0xc9 = 11001001

Check the boards.txt entry, see which fuse byte it is referring to. Check the datasheet and see if changing any bits from 0 to 1 will make a difference.

Did you set the board to the Arduino Uno WiFi Rev 2 in the IDE?

Did you set the board to the Arduino Uno WiFi Rev 2 in the IDE?

Yes, I did. The problem kept popping up.

Ignore the warning, as CrossRoads mentioned, its caused by a mistake in the boards.txt file for the boards that use the Atmega4809 processor.

Apparently fixing the mistake is not a high priority, because its been that way for months, and it has no effect on the operation of the board or your sketch.