This mystery is driving me crazy.
I am using an ATmega328P-PU in standalone, 8 MHz internal, 3.3 V configuration on my custom PCB. The digital pins 1 and 4 (physical 3 and 6 on the IC respectively) are my input pins pulled down by 10K external resistors. I have setup pinMode(pin, INPUT) for both.
Now when the circuit is powered on, this pin 1 is always at 3.3V for some mysterious reason, whereas pin 4 is behaving normally. And as I mentioned I am using external pull down resistors. I checked the whole PCB many times over, but I dint find any issue there.
And when I remove the ATmega328P from my PCB and power it on, I don't get this 3.3V on the same pin on the IC base.
One of the output pins on ATmega328P is connected to an LED which lights up as expected, so I guess the sketch is running just fine.
Please help me out here! I am about to go insane :) .