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Arduino Button Library

https://github.com/JChristensen/JC_Button
README file

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License v3.0 as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/gpl.html

Introduction

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.

The simplest way to use a button with an AVR microcontroller is to wire the button between a GPIO pin and ground, and turn on the AVR internal pullup resistor. The Button class constructor takes four arguments, but three have default values that work for a button wired in this manner.

A derived class, ToggleButton, implements button objects that need only "push-on, push-off" functionality.

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.
Toggle: Demonstrates ToggleButton functionality.

Constructors

Button(pin, dbTime, puEnable, invert)

Description

The constructor defines a button object.

Syntax

Button(pin, dbTime, puEnable, invert);

Required parameter

pin: Arduino pin number that the button is connected to (byte)

Optional parameters

dbTime: Debounce time in milliseconds. Defaults to 25ms if not given. (unsigned long)
puEnable: true to enable the microcontroller's internal pull-up resistor, else false. Defaults to true if not given. (bool)
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. Defaults to true if not given. (bool)

Returns

None.

Example

// button connected from pin 2 to ground, 25ms debounce, pullup enabled, logic inverted
Button myButton(2);

// same as above but this button needs a longer debounce time (50ms)
Button myButton(3, 50);

// a button wired from the MCU pin to Vcc with an external pull-down resistor
Button myButton(4, 25, false, false);

ToggleButton(pin, initialState, dbTime, puEnable, invert)

Description

The constructor defines a toggle button object, which has "push-on, push-off" functionality. The initial state can be on or off. See the section, ToggleButton Library Functions for functions that apply specifically to the ToggleButton object. The ToggleButton class is derived from the Button class, so all Button functions are available, but because it is inherently a more limited concept, the special ToggleButton functions will be most useful, along with begin() and read().

Syntax

ToggleButton(pin, initialState, dbTime, puEnable, invert);

Required parameter

pin: Arduino pin number that the button is connected to (byte)

Optional parameters

initialState: Initial state for the button. Defaults to off (false) if not given. (bool)
dbTime: Debounce time in milliseconds. Defaults to 25ms if not given. (unsigned long)
puEnable: true to enable the microcontroller's internal pull-up resistor, else false. Defaults to true if not given. (bool)
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. Defaults to true if not given. (bool)

Returns

None.

Example

// button connected from pin 2 to ground, initial state off,
// 25ms debounce, pullup enabled, logic inverted
ToggleButton myToggle(2);

// same as above but this button is initially "on" and also
// needs a longer debounce time (50ms).
ToggleButton myToggle(3, true, 50);

// a button wired from the MCU pin to Vcc with an external pull-down resistor,
// initial state is off.
Button myButton(4, false, 25, false, false);

Button Library Functions

begin()

Description

Initializes the Button object and the pin it is connected to.

Syntax

myButton.begin();

Parameters

None.

Returns

None.

Example

myButton.begin();

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 (bool)

Example

myButton.read();

isPressed()

isReleased()

Description

These functions check the button state from the last call to 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 (bool)

Example

if ( myButton.isPressed() )
{
	//do something
}
else
{
	//do something else
}

wasPressed()

wasReleased()

Description

These functions check the button state to see if it changed between the last two calls to read() 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() )
{
	//do something
}

pressedFor(ms)

releasedFor(ms)

Description

These functions 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 (bool)

Example

if ( myButton.pressedFor(1000) )
{
    // button has 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 msLastChange = myButton.lastChange();

ToggleButton Library Functions

changed()

Description

Returns a boolean value (true or false) to indicate whether the toggle button changed state the last time read() was called.

Syntax

myToggle.changed();

Parameters

None.

Returns

true if the toggle state changed, else false (bool)

Example

if (myToggle.changed())
{
    // do something
}
else
{
    // do something different
}

toggleState()

Description

Returns a boolean value (true or false) to indicate the toggle button state as of the last time read() was called.

Syntax

myToggle.toggleState();

Parameters

None.

Returns

true if the toggle is "on", else false (bool)

Example

if (myToggle.toggleState())
{
    // do something
}
else
{
    // do something different
}