modm API documentation
Debouncing Buttons


class  modm::Button< PIN >
 Simple Button More...
class  modm::ButtonGroup< T >

Detailed Description

lbuild module: modm:ui:button

The modm::ButtonGroup class is able to debounce eight buttons at the same time. The buttons have to be low-active. If this isn't the case invert their signal before passing it to the update() method.

The update() method needs to be called periodically for example every 10ms. Preferred in a timer interrupt function.

The detection for long or repeated presses works only correctly for one key at a time. This constraint only applies to buttons listed in the mask variable.

## Mode 1

Timeline ---->
__ _________________ __
getState() ____/ ____/ ____/ ____
isPressed() ----X-------X----------------------X-------
isRepeated() --------------------X--X--X--X-------------
isReleased() -------X----------------------X-------X----
| |__|__|
|_______| /

## Mode 2

Timeline ---->
__ _________________ __
getState() ____/ ____/ ____/ ____
isPressedShort() -------X------------------------------X----
isPressedLong() --------------------X----------------------
isReleased() -------X----------------------X-------X----

Naming Buttons

To name buttons, declare an enum with a bitmask for each button:

#include <modm/math/utils/bit_constants.hpp>
enum ButtonIdentifier
NONE = 0x00,
BUTTON0 = modm::Bit0,
BUTTON1 = modm::Bit1,
BUTTON2 = modm::Bit2,
BUTTON3 = modm::Bit3,
BUTTON4 = modm::Bit4,
BUTTON5 = modm::Bit5,
BUTTON6 = modm::Bit6,
BUTTON7 = modm::Bit7,
ALL = 0xFF,

Pass a ButtonIdentifier to any of ButtonGroup::is**() like so

if(buttongroup_instance.isPressed(BUTTON0)) {
// Do stuff

This implementation is based on the C functions written by Peter Dannegger (see