The Button library is for debouncing and reading momentary contact switches like tactile button switches. "Long presses" of arbitrary length can be detected. Works well in state machine constructs. Use the read() function to read each button in the main loop, which should execute as fast as possible.

Examples

The following example sketches are included with the Button library:

SimpleOnOff: Just turns the Arduino's pin 13 LED on and off.
LongPress: Demonstrates detecting long and short button presses.
UpDown: Counts up or down, one number at a time or rapidly by holding the button down.

Button library functions

Button(pin, puEnable, invert, dbTime)

Description

The constructor defines a button object.

Syntax

Button(pin, puEnable, invert, dbTime);

Parameters

pin: Arduino pin number that the button is connected to (byte) puEnable: true to enable the microcontroller's internal pull-up resistor, else false (boolean) invert: false interprets a high logic level to mean the button is pressed, true interprets a low level as pressed. true should be used when a pull-up resistor is employed, false for a pull-down resistor. (boolean) dbTime: Debounce time in milliseconds (unsigned long)

Returns

None.

Example

Button myButton = Button(2, true, true, 25);	//25 ms debounce

read()

Description

Reads the button and returns a boolean value (true or false) to indicate whether the button is pressed. The read() function needs to execute very frequently in order for the sketch to be responsive. A good place for read() is at the top of loop(). Often, the return value from read() will not be needed if the other functions below are used.

Syntax

myButton.read();

Parameters

None.

Returns

true if the button is pressed, else false (boolean)

Example

myButton.read();

isPressed()

isReleased()

Description

These methods check the button state at the point in time when it was last read, and return false or true accordingly. These functions do not cause the button to be read.

Syntax

myButton.isPressed();
myButton.isReleased();

Parameters

None.

Returns

true or false, depending on whether the button has been pressed (released) or not (boolean)

Example

if ( myButton.isPressed() ) {
	//do some stuff
}
else {
	//do some different stuff
}

wasPressed()

wasReleased()

Description

These methods check the button state to see if it changed between the last two reads and return false or true accordingly. These functions do not cause the button to be read. Note that these functions may be more useful than isPressed() and isReleased() since they actually detect a change in the state of the button, which is usually what we want in order to cause some action.

Syntax

myButton.wasPressed();
myButton.wasReleased();

Parameters

None.

Returns

true or false, depending on whether the button was pressed (released) or not (boolean)

Example

if ( myButton.wasPressed() ) { ...

pressedFor(ms)

releasedFor(ms)

Description

These methods check to see if the button is pressed (or released), and has been in that state for the specified time in milliseconds. Returns false or true accordingly. These functions are useful to detect "long presses". Note that these functions do not cause the button to be read.

Syntax

myButton.pressedFor(ms);
myButton.releasedFor(ms);

Parameters

ms: The number of milliseconds (unsigned long)

Returns

true or false, depending on whether the button was pressed (released) for the specified time (boolean)

Example

if ( myButton.pressedFor(1000) ) {  //has the button been pressed for one second?

lastChange()

Description

Under certain circumstances, it may be useful to know when a button last changed state. lastChange() returns the time the button last changed state, in milliseconds (the value is derived from the Arduino millis() function).

Syntax

myButton.lastChange();

Parameters

None.

Returns

The time in milliseconds when the button last changed state (unsigned long)

Example

unsigned long lastChange = myButton.lastChange();