Atomtimer.c File Reference

From EdWiki

Timer and system tick library

This module implements kernel system tick / clock functionality and timer functionality for kernel and application code.

  • Timer callbacks
    Application and kernel code uses this module to request callbacks at a specific number of system ticks in the future. atomTimerRegister() can be called with a structure filled out requesting callbacks in a specific number of ticks. When the timer expires the requested callback function is called.
  • Thread delays
    Application threads can use atomTimerDelay() to request that the thread delay for the specified number of system ticks. The thread will be put in the timer list and taken off the ready queue. When the timer expires the thread will be made ready-to-run again. This internally uses the same atomTimerRegister() function that is used for registering all timers.
  • System tick / Clock
    This module also implements the system tick. At a predefined interval (SYSTEM_TICKS_PER_SEC) architecture ports arrange for atomTimerTick() to be called. The tick increments the system tick count, which can be queried by application code using atomTimeGet(). On this tick, the registered timer list is checked for any timers which have expired. Those which have expired have their callback functions called. It is also on this system tick that round-robin rescheduling time-slices occur. On exit from the tick interrupt handler the kernel checks whether there are two or more threads ready-to-run at the same priority, and if so uses round-robin to schedule in the next thread. This is in contrast to other (non-timer-tick) interrupts which do not allow for round-robin rescheduling to occur, as they should only occur on a new timer tick.
#include <stdio.h>
#include "atom.h"

Data Structures

struct delay_timer


typedef struct delay_timer DELAY_TIMER


uint8_t atomTimerRegister(ATOM_TIMER *timer_ptr)
uint8_t atomTimerCancel(ATOM_TIMER *timer_ptr)
uint32_t atomTimeGet(void)
void atomTimeSet(uint32_t new_time)
void atomTimerTick(void)
uint8_t atomTimerDelay(uint32_t ticks)