Stm32f4 --- general timer update interrupt

STM32F4 The timer is very powerful , Yes TIME1 and TIME8 Advanced timer, etc , Also have TIME2-TIME5,TIM9-TIM14 And so on , also TIME6 and TIME7 Wait for the basic timer , Total amount 14 There are as many timers .

STM32F4 Timer classification （ common 14 individual ）：

• Advanced timer ：TIME1 、TIME8
• Universal timer ： TIME2-TIME5,TIM9-TIM14
• Basic timer ： TIME6 、 TIME7

STM32F4 General timer Introduction

STM32F4 The universal timer contains a 16 Bit or 32 Bit auto overload counter （CNT）, The counter consists of a programmable prescaler （PSC） drive .

STM32F4 A universal timer can be used for ： Measure the pulse length of the input signal ( Input capture ) Or produce an output waveform ( Output comparison and PWM) etc. .

Use a timer prescaler and RCC Clock controller prescaler , Pulse length and waveform period can be adjusted from a few microseconds to a few milliseconds .

STM32F4 Each universal timer is completely independent , There are no resources shared with each other .

STM3 Common to TIMx (TIM2-TIM5 and TIM9-TIM14) Timer functions include ：

• 16 position /32 position ( only TIM2 and TIM5) Up 、 Down 、 Up / Auto load counter down （TIMx_CNT）, Be careful ：TIM9~TIM14 Only support upward （ Increasing ） Count by .

• 16 Bit programmable ( It can be modified in real time ) Preassigned frequency counter (TIMx_PSC), The frequency division coefficient of the counter clock frequency is 1～65535 Any number between .

• 4 A separate channel （TIMx_CH1_4,TIM9TIM14 most 2 Channels ）, These channels can be used as ：
  A． Input capture
  B． Output comparison
  C．PWM Generate ( Edge or center alignment mode ) , Be careful ：TIM9~TIM14 Middle alignment mode is not supported
  D． Monopulse mode output

• External signals can be used （TIMx_ETR） Control timer and timer Interconnection （ It can be used 1 One timer controls another timer ） The synchronous circuit of .

• Interrupt occurs when the following events occur /DMA（TIM9~TIM14 I won't support it DMA）：
  A． to update ： The counter overflows up / Spilling down , Counter initialization ( Through software or internal / External trigger )
  B． Triggering event ( The counter starts 、 stop it 、 Initialized or internally / External trigger count )
  C． Input capture
  D． Output comparison
  E． Support for incremental positioning ( orthogonal ) Encoder and Hall sensor circuits （TIM9~TIM14 I won't support it ）
  F． Trigger input as an external clock or current management by cycle （TIM9~TIM14 I won't support it ）

STM32F4 Register of general timer

Control register 1

Control register 1（TIMx_CR1）

The description of each bit of this register is shown in Fig

TIMx_CR1 The lowest point of , That is, the counter enable bit , This bit must be set to 1, To get the timer to start counting .

DMA/ Interrupt enable register

DMA/ Interrupt enable register （TIMx_DIER）

The register is a 16 Bit register , Their descriptions are shown in the figure :

The first 0 position , This bit is the update interrupt allowed bit , Update interrupt using timer , This bit needs to be set to 1, To allow interrupts due to update Events .

Prescaler register

Prescaler register （TIMx_PSC）.

This register divides the clock by setting , Then provide it to the counter , As a counter clock . The description of each bit of this register is shown in Fig

here , The clock sources of timers are 4 individual ：
1） Internal clock （CK_INT）
2） External clock mode 1： External input pins （TIx）
3） External clock mode 2： External trigger input （ETR）, Only applicable to TIM2、TIM3、TIM4
4） Internal trigger input （ITRx）： Use A Timer as B Timer prescaler （A by B Provide clock ）.

These clocks , The specific choice can be made by TIMx_SMCR Register to set . there CK_INT The clock is from APB1 Double frequency , Unless APB1 Set the number of clock dividers to 1（ It's not usually 1）, Otherwise, the universal timer TIMx The clock is APB1 Of the clock 2 times , When APB1 When the clock doesn't divide , Universal timer TIMx The clock is equal to APB1 The clock of . The advanced timer and TIM9~TIM11 The clock doesn't come from APB1, But from APB2 Of .

Counter register

TIMx_CNT register , This register is the counter of the timer , This register stores the count value of the current timer .

Auto reload register

Auto reload register （TIMx_ARR）

This register physically corresponds to 2 A register . One is that programmers can operate directly , The other is something that programmers can't see , This invisible register is called shadow register . In fact, what really works is the shadow register . According to the TIMx_CR1 In the register APRE Bit setting ：APRE=0 when , The contents of the preloaded register can be transferred to the shadow at any time
Sub register , here 2 The is connected ; and APRE=1 when , At each update event （UEV） when , Just put the preload register （ARR） The contents of are transferred to the shadow register .

The description of each bit of the automatic reload register is shown in the figure

Status register

Status register （TIMx_SR）

This register is used to mark various events related to the timer / Whether the interruption occurs . The description of each bit of this register is shown in Fig

Configure timer through library function

Timer related library functions mainly focus on firmware library files stm32f4xx_tim.h and stm32f4xx_tim.c In file . The timer configuration steps are as follows ：

TIM3 Clock enable .

TIM3 It's mounted on APB1 under , So pass APB1 The clock enable function under the bus enables TIM3. The function called is ：

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); /// Can make  TIM3  The clock 

Initialize timer parameters , Set auto reload value , Division coefficient , Counting method, etc

In library functions , The initialization parameter of timer is through initialization function TIM_TimeBaseInit Realized ：

voidTIM_TimeBaseInit(TIM_TypeDef*TIMx,
TIM_TimeBaseInitTypeDef* TIM_TimeBaseInitStruct);

The first parameter is to determine which timer

The second initialization parameter is the body parameter of the pointer , The structural type is TIM_TimeBaseInitTypeDef, The definition of this structure ：

typedef struct
{
    
 uint16_t TIM_Prescaler; 
 uint16_t TIM_CounterMode; 
 uint16_t TIM_Period; 
 uint16_t TIM_ClockDivision; 
 uint8_t TIM_RepetitionCounter; 
} TIM_TimeBaseInitTypeDef;

This structure has 5 Member variables , For general timers, only the first four parameters are useful , Last parameter TIM_RepetitionCounter It's the advanced timer that works
The first parameter TIM_Prescaler It is used to set the frequency division coefficient

The second parameter TIM_CounterMode Is used to set the counting mode , It can be set to count up , Down counting and center aligned counting , More commonly used is the up count mode TIM_CounterMode_Up And count down mode TIM_CounterMode_Down.

The third parameter is to set the auto overload count cycle value

The fourth parameter is used to set the clock division factor

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructure.TIM_Period = 5000;
TIM_TimeBaseStructure.TIM_Prescaler =7199; 
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; 
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

Set up TIM3_DIER Allow update interrupt

To use TIM3 The update of , The corresponding bit of the register enables the update interrupt . In the library function, timer interrupt is enabled by TIM_ITConfig Function to implement ：

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

The first parameter is the timer

The second parameter is critical , Is used to indicate the type of timer interrupt that we enable , There are many types of timer interrupts , Including update interrupt TIM_IT_Update, Trigger interrupt TIM_IT_Trigger, And input capture interrupt and so on .

The third parameter is disable or enable .

Can make TIM3 The update of , The format is ：

TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE );

TIM3 Interrupt priority setting .

After timer interrupt enable , Because it's going to interrupt , It's essential to set up NVIC Related registers , Set interrupt priority

Can make TIM3

Start the timer after configuration , adopt TIM3_CR1 Of CEN Bit to set . In the firmware library, the function to enable timer is through TIM_Cmd Function to implement ：

void TIM_Cmd(TIM_TypeDef* TIMx, FunctionalState NewState)

Enable timer 3, Method is ：

TIM_Cmd(TIM3, ENABLE); // Can make  TIMx  peripherals 

Write interrupt service function

In the end , Or write timer interrupt service function , This function is used to process the related interrupt generated by timer .

After the interrupt is generated , The value of the status register is used to determine the type of interrupt generated . Then perform the relevant operations

Use update （ overflow ） interrupt , In the status register SR The lowest point of . After processing the interrupt, it should be directed to TIM3_SR Write at the lowest position of 0, To clear the interrupt flag .

In the firmware library function , The function used to read the value of interrupt status register and judge the type of interrupt is ：

ITStatus TIM_GetITStatus(TIM_TypeDef* TIMx, uint16_t TIM_IT)

The function is to , Judge timer TIMx The interrupt type of TIM_IT Whether there is an interruption . such as , We must judge
Chronometer 3 Whether there is an update （ overflow ） interrupt , Method is ：

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

The function of clearing interrupt flag bit in firmware library is ：

void TIM_ClearITPendingBit(TIM_TypeDef* TIMx, uint16_t TIM_IT)

The function is to , Clear timer TIMx The interrupt TIM_IT Sign a . stay TIM3 After the overflow interrupt of , We want to clear the interrupt flag bit , The method is ：

TIM_ClearITPendingBit(TIM3, TIM_IT_Update );

The firmware library also provides two functions to judge the timer status and clear the timer status flag bit TIM_GetFlagStatus and TIM_ClearFlag, Their role is similar to that of the previous two functions . It's just TIM_GetITStatus The function will first determine whether the interrupt is enabled , Enable to judge the interrupt flag bit , and TIM_GetFlagStatus Directly used to determine the status flag bit .

Code

// Universal timer  3  Interrupt initialization 
//arr： Auto reload value . psc： Clock presplitting frequency 
// Timer overflow time calculation method :Tout=((arr)*(psc))/Ft us.
//Ft= Timer operating frequency , Company :Mhz
// Here's a timer  3!
void TIM3_Int_Init(u16 arr,u16 psc)
{
    
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); // Can make  TIM3  The clock 

TIM_TimeBaseInitStructure.TIM_Period = arr-1; // Automatic reload load value 
TIM_TimeBaseInitStructure.TIM_Prescaler=psc-1; // Timer frequency division 
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up; // Upcount mode 
TIM_TimeBaseInitStructure.TIM_ClockDivision=TIM_CKD_DIV1;

TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStructure);//  Initialize the timer  TIM3

TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE); // Allow timer  3  Update interrupt 

NVIC_InitStructure.NVIC_IRQChannel=TIM3_IRQn; // Timer  3  interrupt 
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0x01; // preemption  1
NVIC_InitStructure.NVIC_IRQChannelSubPriority=0x03; // Response priority  3
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure);//  initialization  NVIC

TIM_Cmd(TIM3,ENABLE); // Enable timer  3

// Timer  3  Interrupt service function 
void TIM3_IRQHandler(void)
{
    
if(TIM_GetITStatus(TIM3,TIM_IT_Update)==SET) // Overflow interrupt 
{
    
	PPS_OUT=1;
	delay_ms(100);	
	PPS_OUT=0;
}
TIM_ClearITPendingBit(TIM3,TIM_IT_Update); // Clears the interrupt flag bit 
}

Contains an interrupt service function and a timer 3 Interrupt initialization function

Of this function 2 Two parameters are used to set TIM3 Overflow time . Because the system is initialized SystemInit The function has been initialized APB1 The clock is 4 frequency division , the
With APB1 The clock is 42M,

When APB1 The number of clock frequency division is 1 When ,TIM2-7 as well as TIM12-14 The clock is APB1 The clock of , And if the APB1 The number of clock divisions is not 1, that TIM2-7 as well as TIM12-14 The clock frequency of will be APB1 Twice the clock . therefore ,TIM3 The clock is 84M, Then according to the design arr and psc Value , You can calculate the interruption time .

The calculation formula is as follows ：

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

among ：
Tclk：TIM3 Input clock frequency （ Unit is Mhz）.
Tout：TIM3 Overflow time （ Unit is s）.

Then in the interrupt function , Judge after interruption , pull up AF10, Time delay 100ms Pull down again .