Sprema ga u neki temp direktorij. U Arduino IDE u File ... Preferences, aktiviraj opciju Show verbose output during ... Compilation i negdje će ti na kraju prikazati puni put do ".hex" fajla. Evo recimo što mi daje kod kompajliranja blink.ino s gore navedenom opcijom:
/tmp/arduino_build_35878/Blink.ino.elf
/tmp/arduino_build_35878/Blink.ino.bin
/tmp/arduino_build_35878/Blink.ino.elf
/tmp/arduino_build_35878/Blink.ino.bin