If there are any issues during the FW upgrade process, check the following
points:
- Note that the upgrade process
will fail if DebugWire is enabled on the megaAVR. Make sure the DW fuse is
un-programmed, and that the ISP fuse is programmed.
- The mEDBG Virtual COM Port must
not be opened in any terminal programs, such as PuTTY or TeraTerm
- Make sure that the mEDBG Virtual
COM Port driver is installed and shows up in the device manager. If it is not
shown, download the drivers via the Extension Manager in Atmel Studio: Tools →
Extension Manager and search for the Atmel USB Installer.