STM32F103 study notes (VII) Timer interrupt (update interrupt)

The timer function of STM32 is very powerful, including TIME1 and TIME8 advanced timers, TIME2~TIME5 general timers, TIME6 and
TIME7 basic timers.

    The general TIMx (TIM2, TIM3, TIM4 and TIM5) timer functions of STM32 include:
1) 16-bit up, down, up/down auto-load counter (TIMx_CNT).
2) 16-bit programmable (can be modified in real time) prescaler (TIMx_PSC), the counter clock frequency division factor is
any value between 1 and 65535.
3) 4 independent channels (TIMx_CH1~4), these channels can be used as:
A. Input capture
B. Output compare
C. PWM generation (edge ​​or center alignment mode)
D. Single pulse mode output
4) External signal (TIMx_ETR) can be used to control the synchronization circuit of timer and timer interconnection (one timer can be used to control another
timer).
5) Interrupt/DMA is generated when the following events occur:
A. Update: counter overflow/underflow, counter initialization (by software or internal/external trigger)
B. Trigger event (counter starts, stops, initializes or counts by internal/external trigger)
C. Input capture
D. Output comparison
E. Support for incremental (quadrature) encoder and Hall sensor circuits for positioning
F. Trigger input as external clock or cycle-by-cycle current management

Next, the time.c file needs to be written:

1. #include "timer.h"  

2. #include "led.h"  

3. //General timer 3 interrupt initialization  

4. //The clock here is selected to be twice that of APB1, and APB1 is 36M  

5. //arr: automatically reload value.  

6. //psc: clock pre-division number  

7. //Timer 3 is used here!  

8. void TIM3_Int_Init(u16 arr,u16 psc)  

9. {  

10.  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  

11. NVIC_InitTypeDef NVIC_InitStructure;  

12. RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //①Clock TIM3 enable  

13. //Timer TIM3 initialization  

14. TIM_TimeBaseStructure.TIM_Period = arr; //Set the value of the automatic reload register period  

15. TIM_TimeBaseStructure.TIM_Prescaler =psc; //Set the prescaler value of the clock frequency divisor  

16. TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //Set clock division  

17. 199  

18. TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM counts up  

19. TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //②Initialize TIM3  

20. TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE); //③Enable update interrupt  

21. //Interrupt priority NVIC setting  

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

23. NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //Preemption priority level 0  

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

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

26. NVIC_Init(&NVIC_InitStructure); //④Initialize NVIC registers  

27. TIM_Cmd(TIM3, ENABLE); //⑤Enable TIM3  

28. }  

29. //Timer 3 interrupt service routine⑥  

30. void TIM3_IRQHandler(void) //TIM3 interrupt  

31. {  

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

33. {  

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

35. LED1=!LED1;  

36. }  

37. }  

I would like to emphasize here that when I was doing the experiment, the program did not report an error, but after burning it, DS0 and DS1 were always off, so I compared the original program to find the error one by one, and finally found that the interrupt service function was written incorrectly, IRQHandler was written as IRQHanlder. At first I was very puzzled, isn’t the interrupt service function name defined by myself, and there is a problem if I write a wrong letter? In fact, it is not the case. I misunderstood how the interrupt function works from the beginning. . .

The interrupt must be initialized first, and then enabled, which is this sentence:

1. TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE ); // Enable update interrupt  

After enabling, it will automatically find and enter the interrupt service function, which means that the interrupt service function has been defined internally. After I wrote it wrong, the program has entered the interrupt service function, but it is stuck inside and can't get out, causing DS1 and DS0 in the main function to not light up... (Comment out the interrupt enable, the interrupt service function of my mistake remains unchanged, and DS0 in the main function lights up after burning)

Next is the main function:

1. int main(void)  

2. {  

3. delay_init(); //delay function initialization   

4. NVIC_Configuration(); //Set NVIC interrupt group 2: 2-bit preemption priority, 2-bit response priority  

5. 200  

6. uart_init(9600); //Serial port initialization baud rate is 9600  

7. LED_Init(); //LED port initialization  

8. TIM3_Int_Init(4999,7199); //10Khz counting frequency, 500ms when counting to 5000  

9.  while(1)  

10. {  

11. LED0=!LED0;  

12. delay_ms(200);   

13. }  

14. }  

The final experimental result is that DS0 and DS1 flash alternately, but DS0 is twice as fast as DS1.