m having 4*4 matrix keypad.how can i scan only 4th row & 4th column? i want to make keypad like my 16th key is common when that key is on then keypad should generate alphabates on uart for 4*4 matrix keypad and when key is off it should generate numeric characters.pls help me
Use this 16th key as a toggle switch (like the caps-lock on the PC keyboard) and store this state in a bit-variable,
which will change the look-up tables (numeric <> alpha).
An additional LED also can be lit to visualise the keyboard state (like on the PC keyboard )
Thus, you can use the usual routines for the 4x4 keypad (no additional HW).