多定時器複用一個硬件定時器

當定時器不夠用或者不想浪費資源時。我們可以利用定時器複用功能。使用一個硬件定時器就可以實現多個時間的定時。類似於軟件定時器。
優點：可以多個定時器複用要給硬件，節約資源
缺點：它是在某個任務或者mian中一直循環查詢。優先級沒有定時器中斷優先級高

/*
 * Copyright (c) 2016 Zibin Zheng <[email protected]>
 * All rights reserved
 */

#include "multi_timer.h"
#include "tim.h"
//timer handle list head.
static struct Timer* head_handle = NULL;

//Timer ticks
static uint32_t _timer_ticks = 0;

/**
  * @brief  Initializes the timer struct handle.
  * @param  handle: the timer handle strcut.
  * @param  timeout_cb: timeout callback.
  * @param  repeat: repeat interval time.
  * @retval None
  */
void timer_init(struct Timer* handle, void(*timeout_cb)(), uint32_t timeout, uint32_t repeat)
{
	// memset(handle, sizeof(struct Timer), 0);
	handle->timeout_cb = timeout_cb;
	handle->timeout = _timer_ticks + timeout;
	handle->repeat = repeat;
}

/**
  * @brief  Start the timer work, add the handle into work list.
  * @param  btn: target handle strcut.
  * @retval 0: succeed. -1: already exist.
  */
int timer_start(struct Timer* handle)
{
	struct Timer* target = head_handle;
	while(target) {
		if(target == handle) return -1;	//already exist.
		target = target->next;
	}
	handle->next = head_handle;
	head_handle = handle;
	return 0;
}

/**
  * @brief  Stop the timer work, remove the handle off work list.
  * @param  handle: target handle strcut.
  * @retval None
  */
void timer_stop(struct Timer* handle)
{
	struct Timer** curr;
	for(curr = &head_handle; *curr; ) {
		struct Timer* entry = *curr;
		if (entry == handle) {
			*curr = entry->next;
//			free(entry);
		} else
			curr = &entry->next;
	}
}

主程序：
/**
  * @brief  main loop.
  * @param  None.
  * @retval None
  */
void timer_loop()
{
	struct Timer* target;
	for(target=head_handle; target; target=target->next) {
		if(_timer_ticks >= target->timeout) {
			if(target->repeat == 0) {
				timer_stop(target);
			} else {
				target->timeout = _timer_ticks + target->repeat;
			}
			target->timeout_cb();
		}
	}
}

/**
  * @brief  background ticks, timer repeat invoking interval 1ms.
  * @param  None.
  * @retval None.
  */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
	if(htim->Instance == TIM4)
	{
		_timer_ticks++;//1ms++
	}
}

void bps_InitTime(void){
	HAL_TIM_Base_Start_IT(&htim4); //使用定時器的時候調用這個函數啓動
}

struct Timer timer1;
struct Timer timer2;

void timer1_callback()
{
    printf("timer1 timeout!\r\n");
}

void timer2_callback()
{
    printf("timer2 timeout!\r\n");
}
int main()
{
	timer_init(&timer1, timer1_callback, 1000, 1000); //1s loop
	timer_start(&timer1);
	
	timer_init(&timer2, timer2_callback, 50, 0); //50ms delay
	timer_start(&timer2);
	bps_InitTime();
	while(1) {
	    
	    timer_loop();
	}
}