Arduino Library – Keypad

library icon


Installatie van Arduino IDE libraries: Arduino info
arduino logo rond

Informatie (ENG)

Keypad is a library for using matrix style keypads with the Arduino. As of version 3.0 it now supports mulitple keypresses.

This library is based upon the Keypad Tutorial.

It was created to promote Hardware Abstraction. It improves readability of the code by hiding the pinMode and digitalRead calls for the user.

Keypad library is part of the Hardware Abstraction libraries.

You won’t need external resistors or diodes because the library uses the internal pullup resistors and additonally ensures that all unused column pins are high-impedance.


Keypad(makeKeymap(userKeymap), row[], col[], rows, cols)

Instantiates a Keypad object that uses pins 5, 4, 3, 2 as row pins, and 8, 7, 6 as column pins.
This keypad has 4 rows and 3 columns, resulting in 12 keys.


void begin(makeKeymap(userKeymap))

Initializes the internal keymap to be equal to userKeymap
[See File -> Examples -> Keypad -> Examples -> CustomKeypad]

char waitForKey()

This function will wait forever until someone presses a key. Warning: It blocks all other code until a key is pressed. That means no blinking LED’s, no LCD screen updates, no nothing with the exception of interrupt routines.

char getKey()

Returns the key that is pressed, if any. This function is non-blocking.

KeyState getState()

Returns the current state of any of the keys.
The four states are IDLE, PRESSED, RELEASED and HOLD.

boolean keyStateChanged()

New in version 2.0: Let’s you know when the key has changed from one state to another. For example, instead of just testing for a valid key you can test for when a key was pressed.

setHoldTime(unsigned int time)

Set the amount of milliseconds the user will have to hold a button until the HOLD state is triggered.

setDebounceTime(unsigned int time)

Set the amount of milliseconds the keypad will wait until it accepts a new keypress/keyEvent. This is the “time delay” debounce method.


Trigger an event if the keypad is used. You can load an example in the Arduino IDE.
[See File -> Examples -> Keypad -> Examples -> EventSerialKeypad] or see the KeypadEvent Example code.

For Now

Here’s the list of multi-keypress functions and the keylist definition.

  • Key key[LIST_MAX]
  • bool getKeys()
  • bool isPressed(char keyChar)
  • int findInList(char keyChar)


How do I use multiple Keypads?

Keypad is a class. Therefore to use multiple Keypad, you must create an instance for each of them. In the example above, the Keypad instance keypad) was bound to the digital pins 2, 3, 4, 5, 6, 7 and 8.

To add a Keypad bound to digital pins 9, 10, 11, 12, 13, 14, 15 and 16, you could create the following instance keypad2:

And now it’s just a matter of using whatever function is wanted on each keypad:

How do I use setDebounceTime(unsigned int time)?

In Arduino follow the main menu from File-> Examples-> Keypad-> Examples->DynamicKeypad. Once the sketch is open find setup() and there you will see:

This shows that the debounce time will allow one key press every 250 milliseconds. If multiple key presses occur within that time frame (as would happen when a key is bouncing) then those extra presses are simply ignored.

Dowload Keypad library @ Github
Download Keypad I2C addons @ Github