The simplest timing configuration of stm32 basic timer

I have recently used the timing function of the timer. I learned that the timer function of stm32 is very powerful and has a lot of things. The datasheet also talks about it in a long paragraph. I will not go into details about it. Here I will only explain how to configure the simplest timing function configuration.

Environment description: MCU: stm32F4 series, using the general timer TIM3

The first thing to know is that TIM3 is mounted on the APB1 bus. For details, see STM32F417xx_datasheet-P.19. There is a block diagram called Device overview. Forget it, let's take a screenshot. 

What is the clock of APB1? It depends on how you configure it. Generally, it is in the SetSysClock() function. Here, I divide the system clock by 4. The system clock is 168MHz, so the clock on APB1 is 42MHz. Don't think that the clock of TIM3 is 42MHz, because APB1 to TIM3 has to go through a multiplier. This multiplier works only when the division coefficient of the previous system clock to APB1 is not 1. As we said before, APB1 is obtained by dividing the system clock by 4, so the multiplier is effective here, so the clock of TIM3 is the multiplication of APB1, that is, 84MHz.

OK, now that we have the input clock for the timer, we only need two parameters to configure the simple function of the timer: the prescaler and the auto-reload value.

Tout = ((arr+1)*(psc+1))/Tclk;

Where arr is the auto-reload value, psc is the pre-division value, and Tclk is the timer clock. 

For example, if I want a 1s timer, I can set: arr = 9999; psc = 8399; 

Here we should pay attention to the value range of arr and psc, the former is u32 and the latter is u16.

  NVIC_InitTypeDef NVIC_InitStructure;

  // TIM3 clock enable 

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  // Enable the TIM3 gloabal Interrupt 

  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x3;

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x3;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);

  TIM_TimeBaseStructure.TIM_Period          = arr;

  TIM_TimeBaseStructure.TIM_Prescaler       = psc;

  TIM_TimeBaseStructure.TIM_ClockDivision   = 0;

  TIM_TimeBaseStructure.TIM_CounterMode     = TIM_CounterMode_Up;

  //Upward counting mode is to count from 0 to arr. When counting to arr, a TIM_IT_Update interrupt is generated. There are other interrupts to choose from.

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* TIM Interrupts enable */

  TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);

  /* TIM3 enable counter */

  TIM_Cmd(TIM3, ENABLE);

In this way, the timer starts working, and then write the interrupt processing function.

void TIM3_IRQHandler(void)

{

    if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET)

    {

        TIM_ClearITPendingBit(TIM3, TIM_IT_Update);

        //your code

    }

}

At this point, the timing function of TIM3 is completed. According to the psc and arr values, we can set the desired timing time. 

Of course, this is just a very simple function of timing. There are many cool things. If there are any mistakes, please correct me!