#define BEEPER_PIN 27 // Pin 27 is taken by LED_PIN, but Melzi LED does nothing with Marlin so this can be used for BEEPER_PIN. You can use this pin with M42 instead of BEEPER_PIN.
#define ORIG_BEEPER_PIN 27 // Pin 27 is taken by LED_PIN, but Melzi LED does nothing with Marlin so this can be used for ORIG_BEEPER_PIN. You can use this pin with M42 instead of ORIG_BEEPER_PIN.