#include const byte rows = 4; //four rows const byte cols = 4; //three columns char keys[rows][cols] = { {'1','2','3','A'}, {'4','5','6','B'}, {'7','8','9','C'}, {'*','0','#','D'} }; byte rowPins[rows] = {9, 8, 7, 6}; //connect to the row pinouts of the keypad byte colPins[cols] = {5, 4, 3, 2}; //connect to the column pinouts of the keypad Keypad customKeypad = Keypad( makeKeymap(keys), rowPins,..