I'm trying to write a simple core to allow you to program a chip (the ATmega1284) using ISP on the Arduino IDE.
I've searched on AVR Freaks and found some excellent tutorials on writing bootloaders, but nothing about empty bootloaders.
Other cores that allow you to program ATtiny and ATmega chips using ISP allow to program the fuses using the Burn Bootloader command in the Arduino IDE, using fuse definitions in the boards.txt file:
attiny85at1.bootloader.low_fuses=0x62 attiny85at1.bootloader.high_fuses=0xD7 attiny85at1.bootloader.extended_fuses=0xFF attiny85at1.bootloader.path=empty attiny85at1.bootloader.file=empty85at1.hex
However, they also provide an empty bootloader file (eg empty85at1.hex), which is not actually empty; the one for the 1MHz ATtiny85 is 942 bytes.
What is this file for, since we are not actually uploading a bootloader?
Will I need to create one for the ATmega1284 if I want to be able to use the Burn Bootloader command to burn the fuses? If so, what does it need to contain?