Hi, I'm rewriting the GRBL library for RAMPS and changing the PINS, however I'm lost on the interrupts ... Is there any guide/info on how to double check I got it OK? Original code #define LIMIT_DDR DDRB #define LIMIT_PORT PORTB #define LIMIT_PIN PINB #define X_LIMIT_BIT 4 // MEGA2560 Digital Pin 10 #define Y_LIMIT_BIT 5 // MEGA2560 Digital Pin 11 #define Z_LIMIT_BIT 6 // MEGA2560 Digital Pin 12 #define LIMIT_INT PCIE0 // Pin change interrupt enable pin #define LIMIT_INT_vect PCINT0_vect #define LIMIT_PCMSK PCMSK0 // Pin change interrupt register New code - changed to PORT E #define LIMIT_DDR DDRE #define LIMIT_PORT PORTE #define LIMIT_PIN PINE #define X_LIMIT_BIT 5 // MEGA2560 Digital Pin 3 #define Y_LIMIT_BIT 4 // MEGA2560 Digital Pin 2 #define Z_LIMIT_BIT 1 // MEGA2560 Digital Pin 1 #define LIMIT_INT PCIE0 // Pin change interrupt enable pin #define LIMIT_INT_vect PCINT0_vect #define LIMIT_PCMSK PCMSK0