ROW0 => PIN_X0 ROW1 => PIN_X1 ROW2 => PIN_X2 ROW3 => PIN_X3 COL0 => PIN_X4 COL1 => PIN_X5 COL2 => PIN_X6 COL3 => PIN_X7 R ROW0 {'1' ,'2' ,'3' ,'A'} R ROW1 {'4' ,'5' ,'6' ,'B'} R ROW2 {'7' ,'8' ,'9' ,'C'} R ROW3 {'*' ,'0' ,'#' ,'D'} COL0 COL1 COL2 COL3 | | | | R R R R |____|_____|___|___+VCC