The 4x4 Keypad is a general purpose 16 button (4x4) matrix keypad. It comes ready to work, simply peel-off the adhesive backing, stick it to your surface and plug it in.
This is a simple application of port manipulation using Arduino to paly with the 4*4 button pad. Before read the code, you'd better see the connection diagram first. We use four digital ports as HIGH voltage scanning the row of button pad and four analog ports to read the column of button pad connected with four pull-down resistors. If button is pressed,the voltage will be HIGH when it is scanned by HIGH voltage concurrently. Otherwise, the voltage is pulled down and will be LOW. Using eight ports totally, we can read 16 buttons.