FAQ – Lehrstuhl für Informatik 4

libspicboard
 #ifndef BUTTON_H
 #define BUTTON_H
  
 #include <stdint.h>
 #include "check.h"
  
 /**
  * \addtogroup Button
  *
  * \brief 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.
  *
  * @{
  * \file button.h
  * \version \$Rev: 7715 $
  */
  
 /**
  * \brief Identifiers for all available buttons
  */
 typedef enum {
     BUTTON0 = 0, /**< Button 0 */
     BUTTON1 = 1  /**< Button 1 */
 } __attribute__ ((__packed__)) BUTTON;
  
 CHECK_ENUM_SIZE(BUTTON, 1)
  
  
 /**
  * \brief States for buttons
  *
  * Pressed and released states for buttons.
  */
 typedef enum {
     UNKNOWN  = 0, /**< Buttonstate is unknown (invalid button?) */
     PRESSED  = 4, /**< Button is pressed  */
     RELEASED = 8  /**< Button is released */
 } __attribute__ ((__packed__)) BUTTONSTATE;
  
 CHECK_ENUM_SIZE(BUTTONSTATE, 1)
  
 /**
  * \brief Events for buttons
  *
  * Down (on press) and up (on release) events for buttons.
  */
 typedef enum {
     ONPRESS   = 0, /**< Button is pressed  */
     ONRELEASE = 2  /**< Button is released */
 } __attribute__ ((__packed__)) BUTTONEVENT;
  
 CHECK_ENUM_SIZE(BUTTONEVENT, 1)
  
 /**
  * \brief 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.
  */
 typedef void (*BUTTONCALLBACK) (BUTTON, BUTTONEVENT);
  
 /**
  * \brief Register a callback function for a button event
  *
  * Interrupts must be enabled to receive the callbacks.
  *
  * \param btn       the id of the button
  * \param eve       the type of event that the callback function should be invoked for.
  * \param callback  pointer to the callback function. This function is called from the
  *                  interrupt handler.
  *
  * \retval 0   success,
  * \retval !0  error
  *
  * \sa sb_button_unregisterCallback
  */
 int8_t sb_button_registerCallback(BUTTON btn, BUTTONEVENT eve, BUTTONCALLBACK callback);
  
 /**
  * \brief Unregister a callback function for a button event
  *
  * \param btn       the id of the button
  * \param eve       the type of event that the callback function should be invoked for.
  * \param callback  pointer to the callback function
  *
  * \return 0 on success, negative value on error
  *
  * \retval  0  success
  * \retval -1  the callback function was not registered with the given button/event combination
  *
  * \sa         sb_button_registerCallback
  */
 int8_t sb_button_unregisterCallback(BUTTON btn, BUTTONEVENT eve, BUTTONCALLBACK callback);
  
 /**
  * \brief Query the current state of a button
  *
  * \param btn  id of the button
  *
  * \return the buttons current state (pressed or released - or unknown if invalid button) as a \ref BUTTONSTATE
  */
 BUTTONSTATE sb_button_getState(BUTTON btn);
  
 /** @}*/
  
 #endif
  