STM32F7 46 G Discovery setting TIM2 to 1 second

Question

I'm learning to programm on an STM32F7 46 G Discovery board using Eclipse as an IDE and STM32CubeMX. I'm trying to set a timer (currently TIM2) to one second without using an ISR. I'd like to get a tick from the timer every second.

Below is what I tried so far:

#include "main.h"
#include "stm32f7xx_hal.h"  

/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim2;

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM2_Init(void);
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim);    

int main(void)
{
    HAL_Init();
    SystemClock_Config(); 
    MX_GPIO_Init();
    MX_TIM2_Init();
    __TIM2_CLK_ENABLE();

   while (1)
   {
       HAL_TIM_PeriodElapsedCallback(&htim2);
   }
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim2)
{
    if (htim2->Instance==TIM2) //check if the interrupt comes from TIM2
        {
           HAL_GPIO_TogglePin(ARDUINO_D2_GPIO_Port,ARDUINO_D2_Pin);
        }
}

static void MX_TIM2_Init(void) /* TIM2 init function */
{
  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 41999; //max 65 536
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 1999;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = 0;
  HAL_TIM_Base_Init(&htim2);
  HAL_TIM_Base_Start(&htim2);

  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;

  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;


   if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
      {
        _Error_Handler(__FILE__, __LINE__);
      }
}

I know that the MCU runs at 42MHz which finally makes the clock run at 84MHz with PLL and I think I already set the Prescaler and the Period (to fix the autoreload time) values accordingly.

Thanks for answering and sorry for any English mistake (it's not my first language)

Answer 1

You don't need to call HAL_TIM_PeriodElapsedCallback() function in while(1) loop. Because it works in non-blocking mode! Instead, you can do something like this if you want to toggle led every one second.

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
   /*Include channel assertion as you did above */
   HAL_GPIO_TogglePin(ARDUINO_D2_GPIO_Port,ARDUINO_D2_Pin);
}

You can simply remove the Callback function call in main().

I don't think you need to enable the clock separately in main() function. It will be enabled in *_hal_msp.c file. Verify that "HAL_TIM_Base_MspInit(TIM_HandleTypeDef *htim)" function has been initialized in *_hal_msp.c file in ./Src folder.

Your timer configuration looks fine for me but for Timer_Clock configuration to be precise, calculate Prescaler value from SystemCoreClock value.

and finally, if you want to trigger an interrupt or create ISR for every 1 second, you can simply use "HAL_TIM_Base_Start_IT()".

Edit: So, I played with it myself a bit and have successfully implemented your program on my STM32E407 board and here is the link! My observation is that you have to start the TIME_BASE in interrupt mode i.e include

  /*##-2- Start the TIM Base generation in interrupt mode **/ 
  if(HAL_TIM_Base_Start_IT(&TimHandle) != HAL_OK)
  {
     /* Starting Error */
     _Error_Handler(__FILE__, __LINE__);
   }

and start TIM2_IRQHandler() in *_it.c and include NVIC priority in *hal_msp.c.

Even I do not particularly know the reason as to why you have to use in interrupt mode. But I guess the Callback function is ISR related.

Edit2: Yes! Check *_tim.c in stdPheripharal library. The PeriodElapsedCallback function is called only in HAL_TIM_IRQHandler(). So, without using interrupt handler, the callback function returns nothing.

Answer 2

Finally solved my issue. Three points were wrong :

• As suggested by Charansai the Callback function must not be called in the loop while(1) (here it stays empty)
• The line HAL_TIM_Base_Start_IT(&htim2); must be added
• The Callback must be put before the main()

In the end the code looks like this :

/* Includes     ---------------------------------------------------------*/
#include "main.h"
#include "stm22f7xx_hal.h"

/*Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim2;

/*Protypes  ---------------------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM2_Init(void);
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)  ;

/*Private functions ---------------------------------------------------------*/
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
    if (htim->Instance==TIM2) //check if the interrupt comes from TIM2
        {
             HAL_GPIO_TogglePin(ARDUINO_D2_GPIO_Port,ARDUINO_D2_Pin);
        }
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_TIM2_Init();

  HAL_TIM_Base_Start_IT(&htim2);

  while (1)
  {
  }
}

/* TIM2 init function */
static void MX_TIM2_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig;
  TIM_MasterConfigTypeDef sMasterConfig;

  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 41999;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 1999;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

  if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

Thanks for answering and highlighting some issues