I just switched from Raspberry Pi 3 to 4, which I use to control some devices. I just discovered that whenever Raspberry pi 4 boots, it changes the pi state of GPIO pin number 3 very fast from low to high to low, which ruins my application.
Is there a way to fix this? Or is this a bug in Pi 4?
Both ports 2 and 3 were having this problem. I moved to another two ports (4, 17) and that fixed the issue. I don't know why 2 and 3 are cursed.
Pins 3,5 on ALL model Pi (GPIO2,3 on 40 pin Pi) have 1.8kΩ pullups on the board, so the state of internal pullups is irrelevant!
They can ONLY be pulled LOW by programming the pin as OUTPUT - this will never happen unless you do something explicit to cause it.
If you have enabled I²C it may change state as SCL is setup.
In any event, using these pins for anything other than their intended purpose (I²C) requires consideration of the impact of the 1.8kΩ pullups.
