Button

Enables event-driven and polling access to the buttons of the SPiCboard. More...

Files
file	button.h

Typedefs
typedef void(*	BUTTONCALLBACK) (BUTTON, BUTTONEVENT)
	Type for button event callback functions. More...

Enumerations
enum	BUTTON { BUTTON0, BUTTON1 }
	Identifiers for all available buttons. More...
enum	BUTTONSTATE { UNKNOWN, PRESSED, RELEASED }
	States for buttons. More...
enum	BUTTONEVENT { ONPRESS, ONRELEASE }
	Events for buttons. More...

Functions
int8_t	sb_button_registerCallback (BUTTON btn, BUTTONEVENT eve, BUTTONCALLBACK callback)
	Register a callback function for a button event. More...
int8_t	sb_button_unregisterCallback (BUTTON btn, BUTTONEVENT eve, BUTTONCALLBACK callback)
	Unregister a callback function for a button event. More...
BUTTONSTATE	sb_button_getState (BUTTON btn)
	Query the current state of a button. More...

Detailed Description

Enables event-driven and polling access to the buttons of the SPiCboard.

The SPiCboard is equipped with two buttons. Button 0 is debounced in hardware, whereas Button 1 needs to be debounced in software by the button module. Debouncing is transparent to the application, that can use both buttons through the provided interface without the need to care about debouncing.

The debouncing code makes use of a timer. When no callbacks are registered for Button 1, the debouncing code is disabled and all alarms registered at the timer should be canceled.

The button module uses dynamic memory management to maintain the callback queues.

Typedef Documentation

BUTTONCALLBACK

typedef void(* BUTTONCALLBACK) (BUTTON, BUTTONEVENT)

Type for button event callback functions.

A button callback function is called on the interrupt level whenever an event at a button occurs that the function was registered for. The callback function is passed the button id and the type of event that occurred. This way, the same callback function can be registered for different buttons and events.

Enumeration Type Documentation

BUTTON

enum BUTTON

Identifiers for all available buttons.

Enumerator
BUTTON0	Button 0
BUTTON1	Button 1

BUTTONEVENT

enum BUTTONEVENT

Events for buttons.

Down (on press) and up (on release) events for buttons.

Enumerator
ONPRESS	Button is pressed
ONRELEASE	Button is released

BUTTONSTATE

enum BUTTONSTATE

States for buttons.

Pressed and released states for buttons.

Enumerator
UNKNOWN	Buttonstate is unknown (invalid button?)
PRESSED	Button is pressed
RELEASED	Button is released

Function Documentation

sb_button_getState()

BUTTONSTATE sb_button_getState

(

BUTTON

btn

)

Query the current state of a button.

Parameters

btn	id of the button

Returns

the buttons current state (pressed or released - or unknown if invalid button) as a BUTTONSTATE

sb_button_registerCallback()

int8_t sb_button_registerCallback	(	BUTTON	btn,
		BUTTONEVENT	eve,
		BUTTONCALLBACK	callback
	)

Register a callback function for a button event.

Interrupts must be enabled to receive the callbacks.

Parameters

btn	the id of the button
eve	the type of event that the callback function should be invoked for.
callback	pointer to the callback function. This function is called from the interrupt handler.

Return values

0	success,
!0	error

See also

sb_button_unregisterCallback

sb_button_unregisterCallback()

int8_t sb_button_unregisterCallback	(	BUTTON	btn,
		BUTTONEVENT	eve,
		BUTTONCALLBACK	callback
	)

Unregister a callback function for a button event.

Parameters

btn	the id of the button
eve	the type of event that the callback function should be invoked for.
callback	pointer to the callback function

Returns

0 on success, negative value on error

Return values

0	success
-1	the callback function was not registered with the given button/event combination

See also

sb_button_registerCallback