JulesGren

Yes, have run it as blank (no ref to bootloader), and as no_bootloader and as uart1 / uart1_def, which is the bootloader installed. There are slight differences, in some cases...

Doesn't appear to work. The 4808 has a bootloader from Arduino installed, if I load with: [env:ATmega4808] platform = atmelmegaavr board = ATmega4808 framework = arduino ;upload_protocol= arduino ;board_hardware.uart =...

Nope, neither of these last two suggestions work. Yes I can write the bootloader Yes I can write the code No I cannot overwrite an existing Arduino bootloader No I...