diodes aren't necessary if only one row is made an output LOW and all others allowed to float. the columns can use internal pull-ups (i.e. INPUT_PULLUP)
a 12x4 matrix would save pins by organizing it as a 7x7 matrix
diodes aren't necessary if only one row is made an output LOW and all others allowed to float. the columns can use internal pull-ups (i.e. INPUT_PULLUP)
a 12x4 matrix would save pins by organizing it as a 7x7 matrix