Preface

The selected column of embedded open source projects published an article on MultiTimer The article , MultiTimer | An infinitely scalable software timer , This week, some friends in the group reminded me MutilTimer It's not quite the same as the article , The first reaction is to reconstruct , After the technical level has been improved by one level, the big guys like reconstruction projects , Go to github See what happened .

master The branch is still the same as before v1 edition , It's the same as the article ：

development The project was refactored on the branch , Released v2 edition ：

Update the next tutorial synchronously .

One 、MultiTimer

The open source project brought to you in this issue is MultiTimer, An infinitely scalable software timer , author 0x1abin, The current harvest 399 individual star, follow MIT Open source license agreement .

MultiTimer Is a software timer extension module , Unlimited expansion of timer tasks you need , Instead of the traditional way of judging the sign bit , It is more elegant and convenient to manage the time trigger sequence of the program .

Project address ：https://github.com/0x1abin/MultiTimer

Two 、 transplant MultiTimer

1. Transplantation ideas

Open source projects mainly refer to the of the project in the migration process readme file , It usually takes only two steps ：

• ① Add the source code to the bare metal project ;
• ② Implement the required interfaces ;

In this article, I use little bear pie IoT Development Kit , The main control chip is STM32L431RCT6：

A bare metal project needs to be prepared before transplantation , I use STM32CubeMX Generate , The following configuration needs to be initialized ：

• Configure a serial port for printing information
• printf Redirect

2.MDK transplant

① Copy MultiTimer Source code into the project ：

② stay keil Add MultiTimer Source file ：

③ take MultiTimer Add header file path to keil in ：

3. gcc transplant

① Copy MultiTimer Source code into the project ：

② stay Makefile Add MultiTimer Source file ：

③ add to MultiTimer Header file path ：

3、 ... and 、 Use MultiTimer

Include header files when using ：

#include "multi_timer.h"

1. Provide Timer Time base signal

MultiTimer The time base signal in needs to be installed ,API as follows ：

/** * @brief Platform ticks function. * * @param ticksFunc ticks function. * @return int 0 on success, -1 on error. */
int MultiTimerInstall(PlatformTicksFunction_t ticksFunc);

PlatformTicksFunction_t The function pointer is defined as follows ：

typedef uint64_t (*PlatformTicksFunction_t)(void);

What is used in this article is STM32HAL library , So pass Systick To provide , No additional timer is required .

Write acquisition system tick Function of ：

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint64_t PlatformTicksGetFunc(void)
{
    
  return (uint64_t)HAL_GetTick();
}
/* USER CODE END 0 */

stay main Install the in the function tick function ：

/* USER CODE BEGIN 2 */
printf("MultiTimer v2 Port on BearPi board by mculover666!\r\n");
MultiTimerInstall(PlatformTicksGetFunc);
/* USER CODE END 2 */

2. establish Timer object

Software timer Abstract MultiTimer Structure ：

struct MultiTimerHandle {
    
    MultiTimer* next;
    uint64_t deadline;
    MultiTimerCallback_t callback;
    void* userData;
};

typedef struct MultiTimerHandle MultiTimer;

So use it directly MultiTimer Type create software timer ：

/* USER CODE BEGIN PV */
MultiTimer timer1;
/* USER CODE END PV */

3. Timer Callback function

Callback function types are defined as follows ：

typedef void (*MultiTimerCallback_t)(MultiTimer* timer, void* userData);

In callback function format , Create timeout callback function ：

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
void timer1_callback(MultiTimer* timer, void* userData)
{
    
    printf("timer1 timeout!\r\n");
}
/* USER CODE END 0 */

4. Initialize and start Timer

Start timer API as follows ：

/** * @brief Start the timer work, add the handle into work list. * * @param timer target handle strcut. * @param timing Set the start time. * @param callback deadline callback. * @param userData user data. * @return int 0: success, -1: fail. */
int MultiTimerStart(MultiTimer* timer, uint64_t timing, MultiTimerCallback_t callback, void* userData);

Initialize timer object , Register timer callback handler , Set timeout （ms）：

/* USER CODE BEGIN 2 */
printf("MultiTimer v2 Port on BearPi board by mculover666!\r\n");
MultiTimerStart(&timer1, 1000, timer1_callback, NULL);
/* USER CODE END 2 */

5. Timer Object processing

Timer Object handler API The definition is as follows ：

/** * @brief Check the timer expried and call callback. * * @return int The next timer expires. */
int MultiTimerYield(void);

Call in main loop Timer Object handler , The processing function will judge whether each timer on the linked list times out , If exceeded , Pull up the registered callback function ：

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
    
  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */
  MultiTimerYield();
}
 /* USER CODE END 3 */

Next, compile and download , See the printed log in the serial port assistant ：

Four 、 How to cycle trigger

In the timer timeout function , Just restart the timer .

void timer1_callback(MultiTimer* timer, void* userData)
{
    
    printf("timer1 timeout!\r\n");

    // restart
    MultiTimerStart(&timer1, 1000, timer1_callback, NULL);
}

5、 ... and 、 Interpretation of design ideas

be relative to v1 edition ,v2 The version obviously involves a lot of brevity ,c File implementation only 4 A function ,82 Line code .

v2 The registration mechanism used in the version is provided by the user tick, One advantage of this design is , More portability , System without intervention tick interrupt , Only MultiTimer When you get scheduled , It can be installed by us API Get system tick, Take this as the benchmark to judge whether the timer times out .

v2 The version also optimizes the linked list insertion mechanism , Before that, it was simple and straightforward to insert nodes into a single linked list , Now sort the inserts by timeout , More elegant ：

In addition to the more elegant insertion , There are also two improvements to the performance of software timers , When scheduling ：

• Timers with a near timeout are always given priority
• The previous timer has not timed out , Scheduling can be ended directly

The implementation idea of software timer can be referred to before v1 Version of the tutorial .

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