【Experiment 6】Timer interrupt experiment

1. Experimental Purpose

1) Familiar with STM32 general timer;

2) Use the timer interrupt to flip the LED light.

2. Introduction to STM32 general timer

The general purpose timer is a 16-bit auto-reload counter driven by a programmable prescaler. It is suitable for many applications, including measuring the pulse length of input signals (input capture) or generating output waveforms (output compare and

PWM). Using the timer prescaler and the RCC clock controller prescaler, the pulse length and waveform period can be adjusted from a few microseconds to a few milliseconds. Each timer is completely independent and does not share any resources with each other. They

Can be operated synchronously together.

The STM32F103 has four general-purpose TIMx (TIM2, TIM3, TIM4 and TIM5). Their functions include:

● 16-bit up, down, up/down auto-load counter

● 16-bit programmable (can be modified in real time) prescaler, the counter clock frequency division factor is any value between 1 and 65536

● 4 independent channels:

─ Input capture

─ Output comparison

─ PWM generation (edge ​​or center aligned mode)

─ Single pulse mode output

● Synchronous circuits that use external signals to control timers and interconnect timers

● Interrupt/DMA is generated when the following events occur:

─ Update: counter overflow/underflow, counter initialization (by software or internal/external trigger)

─ Trigger event (counter starts, stops, initializes, or counts by internal/external trigger)

─ Input capture

─ Output comparison

● Supports incremental (quadrature) encoder and Hall sensor circuits for positioning

● Trigger input as external clock or cycle-by-cycle current management

The functions of the STM32 general-purpose timer are very complex. The ones we generally use more are input capture, output comparison, PWM generation and corresponding interrupts.

Main registers: control register 1 (TIMx_CR1), control register 2 (TIMx_CR2), slave mode control register (TIMx_SMCR), DMA/interrupt enable register (TIMx_DIER), status register (TIMx_SR), event generation register (TIMx_EGR), capture/compare mode register 1 (TIMx_CCMR1), capture/compare mode register 2 (TIMx_CCMR2), capture/compare enable register (TIMx_CCER), capture/compare register 1 (TIMx_CCR1), capture/compare register 2 (TIMx_CCR2), capture/compare register 3 (TIMx_CCR3), capture/compare register 4 (TIMx_CCR4), DMA control register (TIMx_DCR), DMA address of continuous mode (TIMx_DMAR), counter register (TIMx_CNT), prescaler register (TIMx_PSC), automatic load register (TIMx_ARR).

The time base unit contains:

● Counter register (TIMx_CNT)

● Prescaler register (TIMx_PSC)

● Automatic reload register (TIMx_ARR)

Configuration steps:
1) Turn on TIM3 clock and multiplexed function clock, and configure PB5 as multiplexed output.
2) Set TIM3_CH2 to remap to PB5.
3) Initialize TIM3, set ARR and PSC of TIM3.
4) Set PWM mode of TIM3_CH2, and enable CH2 output of TIM3.

5) Enable TIM3.

6) Modify TIM3_CCR2 to control the duty cycle.

3. Hardware Design

Indicator lamp, TIM3

4. Software Design

1. void TIM3_Int_Init(u16 arr,u16 psc)  

2. {  

3.      TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  

4.     NVIC_InitTypeDef NVIC_InitStructure;  

5.   

6.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //Clock enable  

7.       

8.     //Timer TIM3 initialization  

9.     TIM_TimeBaseStructure.TIM_Period = arr; //Set the value of the auto-reload register period to load the activity at the next update event     

10.     TIM_TimeBaseStructure.TIM_Prescaler =psc; //Set the prescaler value used as the TIMx clock frequency divisor  

11.     TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //Set clock division: TDTS = Tck_tim  

12.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM up counting mode  

13.     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //Initialize the time base unit of TIMx according to the specified parameters  

14.    

15.     TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE); //Enable the specified TIM3 interrupt and allow update interrupt  

16.   

17.     //Interrupt priority NVIC setting  

18.     NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn; //TIM3 interrupt  

19.     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //Preempt priority level 0  

20.     NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3; //From priority level 3  

21.     NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ channel is enabled  

22.     NVIC_Init(&NVIC_InitStructure); //Initialize NVIC registers  

23.   

24.   

25.     TIM_Cmd(TIM3, ENABLE); //Enable TIMx                       

26. }  

27. //Timer 3 interrupt service routine  

28. void TIM3_IRQHandler(void) //TIM3 interrupt  

29. {  

30.     if (TIM_GetITStatus(TIM3, TIM_IT_Update) != RESET) //Check whether TIM3 update interrupt occurs  

31.         {  

32.         TIM_ClearITPendingBit(TIM3, TIM_IT_Update ); //Clear TIMx update interrupt flag   

33.         LED1=!LED1;  

34.         }  

35. }  

V. Experimental Results

success!