I am taking a microcontroller class in university and have the following problem:
(Sorry for the poor image quality)
Its fairly simple but here is my problem: In my solution I set the internal pullup resistors on the input pins. I realise you don't need to because of the presence of the external pullups but I though it would be safe to do nonetheless. From my perspective, enabling the the internal pullups does not affect the operation of the circuit, however apparently the correct answer is that the internal pullups should be disabled and I'm not sure why. Isn't it a good idea to have the internal pullups enabled for redundancy so in case something happens to the external pullups the input pins still have a defined state?