On all Arduinos except the DUE, attachInterrupt() does not use the pin number as first argument but the interrupt number, which is different:
void attachInterrupt(uint8_t interrupt, void (*ISR)(void), int mode);
As documented on Arduino reference, for an Arduino UNO, the mapping is as follows:
- Interrupt 0 -> Pin 2
- Interrupt 1 -> Pin 3
So just change the code in setup() to:
attachInterrupt(0, inter, CHANGE);
And that should work for pin 2.
