Well I have been struggling with this for 3 days of googling. I want to be able to actively change the internal pull-ups and pull-downs in a C++ program. Is this not possible without loading another Device Tree overlay. The reason why is that i am working with a 4x4 keypad and the normal way to read them is to set all the columns to high via internal pull up and then read the state of the columns. This why i need a runtime method. I am running the latest version of Debian 8.3 OS on an A5A board.