General-purpose timer for STM32 microcontroller

There are a variety of timers in STM32, which are divided into two advanced controller timers, four normal timers, two basic timers, two watchdog timers, and one system tick timer SysTick.

The key to the timer is the calculation of the timing time. For example, when the timer is used to control the switch of the relay, it takes a period of time to turn off or on, and the timing of the timer cannot be separated.

General purpose timer timing calculation. The basic implementation of a 1 second interrupt:

The input clock of the general-purpose timer module is divided to obtain the counter clock, which is represented by CK_CNT. The coefficient of the pre-divider is: TIMx_PSC. When TIMx_PSC=0, it means no frequency division, when =1, it is divided by 2. And so on.

The formula is: CK_CNT=fclk_PSC/(PSC[15:0]+1), where the PSC is at most 65535.

Followed by the setting of the count value of the TIM5 counter, the TIM5 counter counts with CK_CNT as the clock. Counting to the set value generates an interrupt.

(1/Counter clock after counting) *Count value = set time. Take 1 second as an example

(1/(72MHz/7200))*10000=1s

Initialize an important structure of the general-purpose timer TIM_TimeBaseInitTypeDef

Typedefstruct { u16TIM_Period; / / automatically loaded count value, u16TIM_Prescaler; / / frequency value, when 0 means no frequency, so to subtract 1. u8TIM_ClockDivision; / / set the clock split, u16TIM_CounterMode; / / up, down, etc. Count mode}TIM_TimeBaseInitTypeDef;

Call the function after initializing the structure

Void TIM_TimeBaseInit(TIM_TypeDef* TIMx, TIM_TimeBaseInitTypeDef * TIM_TimeBaseInitStruct) Initializes the TIMx timer time base unit.

The second step is to clear the interrupt pending bit. The function void TIM_ClearITPendingBit(TIM_TypeDef* TIMx, u16 TIM_IT) does the job. Where TIM_IT: The TIM to be checked interrupts the pending bit.

TIM_FLAG_Update//TIM Overflow Interrupt Flag Bit TIM_FLAG_CC1//TIM Capture/Compare 1 Flag Bit TIM_FLAG_CC2//TIM Capture/Compare 2 Flag Bit TIM_FLAG_CC3//TIM Capture/Compare 3 Flag Bit TIM_FLAG_CC4//TIM Capture/Compare 4 Flag Bit TIM_FLAG_Trigger/ /TIM trigger flag bit TIM_FLAG_CC1OF//TIM capture/compare 1 overflow flag TIM_FLAG_CC2OF//TIM capture/compare 2 overflow flag TIM_FLAG_CC3OF//TIM capture/compare 3 overflow flag TIM_FLAG_CC4OF//TIM capture/compare 4 overflow flag

Void TIM_ITConfig(TIM_TypeDef* TIMx, u16 TIM_IT, FunctionalState NewState) Enables/disables the interrupt specified by the TIM, such as:

TIM_ITConfig(TIMx, TIM_IT_Update, ENABLE) // Enable TIMx specified interrupt TIM_Cmd (TIMx, ENABLE); // Counter enabled, start working

In the interrupt processing, check if the specified TIM interrupt occurs or not.

If(TIM_GetITStatus(TIM5,TIM_IT_Update)!=RESET)//Check if the specified TIM interrupt occurs { TIM_ClearITPendingBit(TIM5,TIM_IT_Update);//Clear TIMx interrupt pending bit dosomething......//Do something }