STM8 timer TIM1 timing

The TIM1 timer of ST's STM8 microcontroller is a 16-bit advanced control timer that can be used to achieve basic timing and PWM wave generation. Here we mainly analyze the basic timing function.

Let's first look at the initialization function of the TIM1 timer in the library function provided by ST

void TIM1_TimeBaseInit(uint16_t TIM1_Prescaler,

                       TIM1_CounterMode_TypeDef TIM1_CounterMode,

                       uint16_t TIM1_Period,

                       uint8_t TIM1_RepetitionCounter)

Among them, TIM1_Prescaler is a 16-bit frequency division configuration, and the input value can be 0-65535. This value is finally written into the TIM1_PSCR register, and the formula for calculating the timer frequency is: fcnk = fsys/(PSCR[15:0]+1), where fsys is the system clock frequency and PSCR[15:0] is the 16-bit value of the TIM1_PSCR register;

TIM1_CounterMode is the counting mode, there are 5 modes in total, namely:

TIM1_COUNTERMODE_UP Up counting mode

TIM1_COUNTERMODE_DOWN Down counting mode

TIM1_COUNTERMODE_CENTERALIGNED1    

TIM1_COUNTERMODE_CENTERALIGNED2    

TIM1_COUNTERMODE_CENTERALIGNED3    

TIM1_Period, count value, this item can take any value from 1 to 65535

TIM1_RepetitionCounter, the number of repetition counts. This item can take any value from 0 to 255.

Assuming our system clock is 8Mhz and we set the timer to 1 second, then our initialization settings should be:  

TIM1_TimeBaseInit(7,TIM1_COUNTERMODE_UP,1000,100)；

Time calculation:

The frequency of the timer fcnk = 8Mhz/(7+1) = 1Mhz, which means that one count is 1us, 1000 counts are 1ms, and if the count is repeated 100 times, the interrupt timing time is 100ms. In order to achieve the effect of 1s, we also need to make a judgment 10 times in the interrupt function.

Interrupt function code implementation

INTERRUPT_HANDLER(TIM1_UPD_OVF_TRG_BRK_IRQHandler, 11)

{ 

  count_number++;

  if(count_number < 10）

  {

  }

  else

  {

       count_number = 0; //1 second timer has been reached

  }  

  TIM1_ClearITPendingBit(TIM1_IT_UPDATE);

}

The following is the relevant code to implement 1S timing

/*********************

*Function name: TIM_Config

*Function description: timer configuration

*Parameter Description:

* Input parameters None

* Output parameters None

*********************/

void TIM_Config(void)

{

  TIM1_DeInit();

  TIM1_TimeBaseInit(7,TIM1_COUNTERMODE_UP,1000,100);

  TIM1_ARRPreloadConfig(ENABLE);

  TIM1_ITConfig(TIM1_IT_UPDATE,ENABLE);

  TIM1_Cmd(ENABLE);

}

/**

  * @brief Timer1 Update/Overflow/Trigger/Break Interrupt routine.

  * @param  None

  * @retval None

  */

INTERRUPT_HANDLER(TIM1_UPD_OVF_TRG_BRK_IRQHandler, 11)

{

  /* In order to detect unexpected events during development,

     it is recommended to set a breakpoint on the following instruction.

  */

  count_number++;

  if(count_number < 10)

  {

  }

  else

  {

    count_number = 0;  

  }  

  TIM1_ClearITPendingBit(TIM1_IT_UPDATE);

}