4x4 Keypad
A 4x4 keypad is a matrix of 16 buttons arranged as four rows and four columns.
Part images
What it is
A 4x4 keypad is a matrix of 16 buttons arranged as four rows and four columns.
How students use it
Students use it for passcodes, menus, calculators, number games, and projects that need many buttons without spending sixteen GPIO pins.
Pins and power
Eight useful lines: four rows and four columns. Each key connects one row to one column when pressed.
Passive switch matrix. Use 3.3V-safe GPIO scanning with pull-up or pull-down inputs.
Scan one side of the matrix at a time and read the other side. Pull-up or pull-down resistors keep unpressed inputs from floating.
Voltage and safety
Keep all row and column lines on Pico-safe 3.3V GPIO. Do not mix keypad scanning with external voltages.
Power off before moving ribbon/header wiring. Do not pull hard on the membrane tail.
Module internals
Sixteen button contacts, row conductors, column conductors, flexible membrane, printed labels, and an eight-line header/ribbon connection.
Datasheet notes
SunFounder explains the row-column matrix behavior but does not list a manufacturer part number for the keypad.
Common libraries
No required library. A small scanner loop using machine.Pin is enough; debounce and key-repeat behavior should be deliberate.
Common mistakes
Reversing row/column order, leaving inputs floating, scanning too fast without debounce, and not handling two-key ghosting behavior.