Pull-up Resistor vs Pull-down - Differences, Arduino Guide - Latest Open Tech From Seeed
Pull-up Resistors - SparkFun Learn
Pull-up / Pull-down resistor
Using Pushbuttons with Arduino. Pullup vs Pulldown resistors - Hackster.io
In a circuit with a switch and a pull-down resistor, why does the high impedance of the input not discourage current from flowing into pin? - Arduino Stack Exchange