Custom Arduino Core for Arpmini boards (or any ATmega32u4-based board) using a 512-byte bootloader (nanoBoot), replacing the default "Caterina" bootloader, freeing up 3.5 KB of flash memory!
(Source code for the bootloader and upload tool are included)
This core can be installed using the boards manager. The boards manager URL is:
https://github.com/PaoloEstorm/Arpmini-Core/raw/refs/heads/main/package_arpminicore_index.json
File->Preferences on a PC, or Arduino->Preferences on a Mac, enter the above URL in "Additional Boards Manager URLs Tools -> Boards -> Boards Manager... Select "Arpmini Core by Paolo Estorm" and click "Install".
(the bootloader must be burned using an ISP)
