timer.h Source File

Go to the documentation of this file.
 #ifndef TIMER_H
 #define TIMER_H
 #include <stdint.h>
 
 /**  
  * \addtogroup Timer Timer module
  *
  * \brief The timer module provides an event interface to the hardware timers.
  *
  * The module uses the 16-bit <b>timer 1</b> of the ATmega32. The timer is dynamically
  * configured as needed by the registered alarms and should always be clocked
  * as slow as possible to keep the interrupt load low. When no alarms are
  * registered, the timer clock is disabled.
  *
  * \note The timer module uses dynamic memory management (malloc()/free()) for the allocation
  * of the ALARM types. This is also done from within ISRs. Thus care must be taken when
  * calling malloc()/free() with interrupts enabled.
  *
  * \note Interrupts must be enabled for the timer to work.
  *
  * @{
  * \file timer.h
  * \version \$Rev$
  */
 
 /**
  * \brief ALARM type
  * This is type of a struct containing information about an alarm.
  */
 typedef struct ALARM ALARM;
 
 /**
  * \brief Type for alarm callback functions.
  *
  * Alarm callback functions are invoked on the interrupt
  * level whenever the associated alarm expires. The
  * programming model for callback functions is similar
  * to that of interrupt service routines.
  */
 typedef void (*alarmcallback_t) (void);
 
 /**
  * \brief Cancel an alarm.
  *
  * \param alrm identifier of the alarm that should be canceled
  * \retval  0  success
  * \retval -1  an error occurred
  * \sa sb_timer_setAlarm
  * \note alarms must not be canceled twice
  */
 int8_t sb_timer_cancelAlarm(ALARM *alrm);
 
 /**
  * \brief Create a new alarm.
  *
  * This function can be used to set single shot, as well as repeating timers.
  * 
  * - <b>Single shot:</b> Set cycle to 0. This alarm <b>must not</b> be canceled after being fired.
  * - <b>Repetitive:</b> The first shot can be adjusted be setting alarmtime > 0. Otherwise cycle is used.
  *
  * \note The callback function is called from within the ISR-context.
  *
  * \param callback  callback function that will be invoked whenever the alarm expires
  * \param alarmtime time in ms relative to the current time when the alarm shall expire the first time.
  *                    If set to 0 cycle time will be used.
  * \param cycle     time in ms for alarms that periodically expire after the first regular expiry.
  *                     Set to 0 for single shot timers.
  * \return the identifier of the alarm, or NULL if creating the alarm failed.
  *
  * \warning  Canceling a timer twice or canceling a single shot timer after its expiry may
  *         cause unexpected results.
  *
  * \sa  sb_timer_cancelAlarm
  */
 ALARM *sb_timer_setAlarm(alarmcallback_t callback, uint16_t alarmtime, uint16_t cycle);
 
 /**
  *
  *  \brief waits for a specific number of ms
  *
  * This function must not be invoked with interrupts disabled, i.e. from an interrupt
  * handler (or generally, from the ISR level) or a critical section of the application.
  *
  * The CPU is set in sleep mode while waiting.
  *
  * \param waittime wait time in ms 
  * \retval  0  success
  * \retval -1  alarm could not be activated
  * \retval -2  sb_timer_delay invoked while interrupts disabled
  * \sa sb_timer_delay_abort
  *
  */
 int8_t sb_timer_delay(uint16_t waittime);
 
 /**
  * \brief Aborts an active sb_timer_delay.
  *
  * This function must be invoked on the ISR level.
  *
  * \sa sb_timer_delay
  */
 void sb_timer_delay_abort();
 
 /** @}*/
 
 #endif
 
SPiCboard library (libspicboard, revision exportiert) API documentation
