Getting ATMEL-ICE to work on macOS (verified with Catalina 10.15.7)

MacOS may grab the Atmel-ICE USB device and prevent access. Folllow these instructions (found here):

Preparation: Download the AtmelICE.kext.zip and unzip it. Open a Terminal and change directory (cd) to the folder where you unzipped it

1. sudo chown -R root:wheel AtmelICE.kext
2. sudo mv AtmelICE.kext /Library/Extensions/AtmelICE.kext
3. sudo kextload /Library/Extensions/AtmelICE.kext

If you get a permissions error:

1. sudo rm -rf /Library/Extensions/AtmelICE.kext
2. Restart the Mac and get into recovery mode (hold down CMD + R while booting)
3. Mount the OS drive by choosing the Disk Utility, select the drive and mount it from the menu.
4. Open a terminal by going to the Utilities menu at the top of the screen and then Terminal
5. Remove the driver from /Volumes/your volume/Library/StagedExtensions/Library/Extensions rm -rf /Volumes/your volume/Library/StagedExtensions/Library/Extensions/AtmelICE.kext
6. Close the terminal and restart the computer
7. Follow the steps (1…3) in the first part of this post and you should have a working driver

Test with avrdude (e.g. for ATmega2560):

avrdude -c atmelice_isp -p ATmega2560

Expected output is something similar to:

avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e9801 (probably m2560)
avrdude: safemode: Fuses OK (E:FD, H:D8, L:FF)
avrdude done.  Thank you.