STM32 Introduction - General Timer Configuration

Benefits of Universal Timer

 Tout= ((arr+1)*(psc+1))/Tclk；

TIM3 clock enable

TIM3 is mounted under APB1, so we enable TIM3 through the clock enable function under the APB1 bus. The function called is:

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //Clock enable

Initialize timer parameters, set auto-reload value, frequency division factor, and counting mode.

In the library function, the timer initialization parameters are implemented through the initialization function TIM_TimeBaseInit:

voidTIM_TimeBaseInit(TIM_TypeDef*TIMx,TIM_TimeBaseInitTypeDef* TIM_TimeBaseInitStruct);

The first parameter is to determine which timer it is, which is relatively easy to understand. The second parameter is the timer initialization parameter structure pointer, the structure type is TIM_TimeBaseInitTypeDef

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_TimeBaseStructure.TIM_Period = 5000; //Set the automatic reload count period value

TIM_TimeBaseStructure.TIM_Prescaler =7199; //Parameter TIM_Prescaler is used to set the frequency division coefficient

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //Set the clock division factor

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //Parameter TIM_CounterMode is used to set the counting mode

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

Setting TIM3_DIER enables update interrupts.

Because we want to use the update interrupt of TIM3, the corresponding bit of the register can enable the update interrupt. In the library function, the timer interrupt enable is implemented through the TIM_ITConfig function:

void TIM_ITConfig(TIM_TypeDef* TIMx, uint16_t TIM_IT, FunctionalState NewState)；

The first parameter is to select the timer number, which is easy to understand. The value is TIM1~TIM17.

The second parameter is very critical. It is used to indicate the type of timer interrupt we enable. There are many types of timer interrupts, including update interrupt TIM_IT_Update, trigger interrupt TIM_IT_Trigger, and input capture interrupt, etc.

The third parameter is very simple, which is whether to disable or enable.

TIM3 interrupt priority setting.

After the timer interrupt is enabled, in order to generate an interrupt, it is necessary to set the NVIC related registers.

Interrupt priority.

Enable TIM3.

It is not enough to just configure the timer. If the timer is not enabled, it will not work. We need to enable the timer after configuration by setting the CEN bit of TIM3_CR1. In the firmware library, the function to enable the timer is implemented by the TIM_Cmd function:

void TIM_Cmd(TIM_TypeDef* TIMx, FunctionalState NewState)

Write an interrupt service function.

Function to read the value of the interrupt status register to determine the interrupt type

ITStatus TIM_GetITStatus(TIM_TypeDef* TIMx, uint16_t)

The function is to determine whether the interrupt type TIM_IT of the timer TIMx has an interrupt if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET){}

Function to clear interrupt flag in firmware library

void TIM_ClearITPendingBit(TIM_TypeDef* TIMx, uint16_t TIM_IT)

The function is to clear the interrupt TIM_IT flag of timer TIMx. TIM_ClearITPendingBit(TIM3, TIM_IT_Update);