i connected CLK to the atmega1284 DIP's pin 3 (D2 / INT2), however the interrupt number calculated in PS2Keyboard::begin() was 0, not 2 as expected. took me an awfully long time to realise why ps2interrupt() wasn't called..

i got the desired value by using digitalPinToInterrupt(irq_pin) instead of what most of begin() does - is there any reason not to use the arduino-provided function?