Basic introduction to stm32 timer

f4:

stm32 timer clock frequency

Because the system initialization SystemInit function has initialized the clock of APB1 to divide by 4, the clock of APB1 is 42M, and from the internal clock tree diagram of STM32F4 (above):
（1) When the clock division number of APB1 is 1, the clocks of TIM2~7 and TIM12~14 are the clocks of APB1.
(2) And if the clock division number of APB1 is not 1, then the clock frequency of TIM2~7 and TIM12~14 will be twice the clock frequency of APB1

It should also be noted here that the advanced timers and the clocks of TIM9~TIM11 are not coming
is from APB1, but from APB2. (The clock frequency of the timer is similar to APB1)

Calculation of timer overflow time:
Tout= ((arr+1)*(psc+1))/Tclk；
where:
Tclk: TIM input clock frequency (unit is hz).
Tout: TIM overflow time (unit: s).

E.g:

Timer 3 as an example

  void TIM3_Int_Init(u16 arr,u16 psc)
  {
      TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
      NVIC_InitTypeDef NVIC_InitStructure;
      RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); //①Enable TIM3 clock
             TIM_TimeBaseInitStructure.TIM_Period = arr; //Automatic reload value
             TIM_TimeBaseInitStructure.TIM_Prescaler=psc; //Timer division
	 TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up; //Up counting mode
	TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1;
	 TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStructure);// ②Initialize the timer TIM3
	 TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE); //③Allow timer 3 update interrupt
	 NVIC_InitStructure.NVIC_IRQChannel=TIM3_IRQn; //Timer 3 interrupt
	 NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0x01; //Preemption priority 1
	 NVIC_InitStructure.NVIC_IRQChannelSubPriority=0x03; //Response priority 3
	NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
	 NVIC_Init(&NVIC_InitStructure);// ④Initialize NVIC
	 TIM_Cmd(TIM3,ENABLE); //⑤Enable timer 3
  }

Call the function TIM3_Int_Init(5000-1,8400-1) in the main function;
Its overflow time is calculated as follows:
The timer clock is 84M, the frequency division factor is 8400, so 84M/8400=10Khz counting frequency, counting 5000 times is 500ms.