Few reminders when designing an uC-project:

Inputs

General on inputs:

• Primarily use first all external interrupt and analog pins. Make pads for unused “special” pins, for example external input/analog-pins.

Pulse measuring:

• Do you need to measure pulses? Use external interrupts whenever possible, they are simple to do and really accurate

Outputs:

• If generating pulse out by delay remember that interrupts make the signal jitter.