General purpose timer (interrupt function and PWM output)

Table of contents:

1 Overview

2: Common interrupt functions

3: PWM output 

1 Overview

In development, timers are widely used, which can be simply summarized into three aspects:

1.1: Application of interrupt function. Timer interrupt is commonly used to realize timing, timekeeping, delay and timeout judgment. The various methods of using kernel timer are summarized in the previous blog post;

1.2: Comparison output, the common application is PWM output, using pulse width modulation to achieve the control of LEDs, motors, etc.;

1.3: Input capture, which can capture the input square wave signal, count the waveform period and duty cycle. The most common use is gating, which converts the external analog quantity into a digital quantity (the count value of the timer);

2: Common interrupt functions

The detailed reference manual for the timer initialization is as follows. The main point is to determine the timer overflow period. The overflow frequency of the timer can be calculated using the formula: Tout = (arr+1)*(psc+1)/Tclk.

The following code is implemented: the LED is flipped in the interrupt function, the flip frequency is 1HZ, that is, the LED flashing frequency is 1HZ;

timer_driver.c

1. #include "timer_driver.h"  

2. #include "led_driver.h"  

3.   

4. void TIM3_Init(unsigned int arr,unsigned int psc)  

5. {  

6.   TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  

7.     NVIC_InitTypeDef NVIC_InitStructure;  

8.     TIM_OCInitTypeDef TIM_OCInitStruct;  

9.       

10.     GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); //Map CH2 of TIM3 to PB5  

11.       

12.     //Timer TIM3 initialization  

13.     TIM_TimeBaseStructure.TIM_Period = arr;   

14.     TIM_TimeBaseStructure.TIM_Prescaler =psc;  

15.     TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;  

16.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;   

17.     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);  

18.       

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

20.   

21.     //Interrupt priority NVIC setting  

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

23.     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3; //Preempt 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); //Initialize NVIC registers  

27.   

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

29. }  

30.   

31. unsigned char flag = 0;  

32. void TIM3_IRQHandler(void)   

33. {  

34.         flag = !flag;  

35.         if(flag == 0)  

36.         {  

37.             LED1_ON;  

38.             LED2_ON;  

39.             LED3_ON;  

40.         }  

41.         else  

42.         {  

43.             LED1_OFF;  

44.             LED2_OFF;  

45.             LED3_OFF;  

46.         }  

47.         TIM_ClearITPendingBit(TIM3,TIM_IT_Update);  

48. }  

main.c

1. #include "stm32f10x.h"  

2. #include "timer_driver.h"  

3. #include "led_driver.h"  

4. #include "systick_driver.h"  

5. #include "key_board.h"  

6.   

7. unsigned int led_pwm_ctr_cnt = 0;  

8. unsigned int led_pwm = 0;  

9.   

10. /*Peripheral clock initialization*/  

11. void RCC_PeriphClock_Config(void)  

12. {  

13.     /*GPIO port clock initialization*/  

14.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOD, ENABLE);  

15.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);  

16. }  

17.   

18. int main()  

19. {  

20.     NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //Set interrupt priority group  

21.     SysTick_Init(INT_10MS,SysTick_CLKSource_HCLK_Div8); //Core tick timer configuration for LED task round robin   

22.     RCC_PeriphClock_Config();  

23.     Led_Init(); //LED light initialization   

24.     TIM3_Init(9999,7199); //Timer 3 initialization, overflow frequency is 1hz  

25.       

26.     while(1)  

27.     {  

28.         ;  

29.     }  

30. }  

3: PWM output

There are two things to determine for pwm output: the period of the PWM output waveform and the duty cycle of the PWM output waveform. Specifically, the effective level of the PWM waveform and the PWM output mode need to be set.

The following code implements 1khz pwm waveform output, and the duty cycle of the pwm wave can be changed through security inspection;

timer_driver.c

1. #include "timer_driver.h"  

2. #include "led_driver.h"  

3.   

4. void TIM3_Init(unsigned int arr,unsigned int psc)  

5. {  

6.   TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  

7.     TIM_OCInitTypeDef TIM_OCInitStruct;  

8.       

9.     GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); //Map CH2 of TIM3 to PB5  

10.       

11.     //Timer TIM3 initialization  

12.     TIM_TimeBaseStructure.TIM_Period = arr;   

13.     TIM_TimeBaseStructure.TIM_Prescaler =psc;  

14.     TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;  

15.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;   

16.     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);  

17.       

18.     //PWM CH2 output initialization  

19.     TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM2; /*The high level LED of the development board is on because the upward counting mode is set, and the effective level of OC1 is set to high level. According to the manual, it is set to PWM mode 2*/  

20.     TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable; /*Set OC2 output enable*/  

21.     TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_Low; /*Set OC2 valid level to low level*/  

22.     TIM_OC2Init(TIM3, &TIM_OCInitStruct);  

23.       

24. // //PWM CH1 output initialization  

25. // TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM2; /*The high level LED of the development board is on because the upward counting mode is set, and the OC1 effective level is set to high level. According to the manual, it is set to PWM mode 2*/  

26. // TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable; /*Set OC1 output enable*/  

27. // TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_Low; /*Set OC1 valid level to low level*/  

28. // TIM_OC1Init(TIM3, &TIM_OCInitStruct);  

29.   

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

31.   

32.     TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable); /*Enable the preload function of output compare 2*/   

33.     //TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable); /*Enable the preload function of output compare 2*/   

34.       

35.     TIM_SetCompare2(TIM3, 500);  

36.     //TIM_SetCompare1(TIM3, 500);  

37. }  

main.c

1. #include "stm32f10x.h"  

2. #include "timer_driver.h"  

3. #include "led_driver.h"  

4. #include "systick_driver.h"  

5. #include "key_board.h"  

6.   

7. unsigned int led_pwm_ctr_cnt = 0;  

8. unsigned int led_pwm = 500;  

9.   

10. /*Peripheral clock initialization*/  

11. void RCC_PeriphClock_Config(void)  

12. {  

13.     /*GPIO port clock initialization*/  

14.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO, ENABLE);  

15.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);  

16. }  

17.   

18. int main()  

19. {  

20.     NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //Set interrupt priority group  

21.     SysTick_Init(INT_10MS,SysTick_CLKSource_HCLK_Div8); //Core tick timer configuration for LED task round robin   

22.     RCC_PeriphClock_Config();  

23.     Led_Init(); //LED light initialization   

24.     Key_Init();  

25.     TIM3_Init(999,71); //Timer 3 initialization, pwm cycle is 1KHZ  

26.       

27.     while(1)  

28.     {  

29.         if(led_pwm_ctr_cnt >= 1) //500ms polling  

30.         {  

31.             led_pwm_ctr_cnt = 0;  

32.             if(K1 == 0) //k1 button is pressed  

33.             {  

34.                 if(led_pwm < 1000)  

35.                     led_pwm++;  

36.                 TIM_SetCompare2(TIM3, led_pwm);  

37.                 TIM_SetCompare1(TIM3, led_pwm);  

38.             }  

39.             else  

40.             if(K2 == 0)  

41.             {  

42.                 if(led_pwm > 0)  

43.                     led_pwm--;  

44.                 TIM_SetCompare2(TIM3, led_pwm);  

45.                 TIM_SetCompare1(TIM3, led_pwm);  

46.             }  

47.         }  

48.     }  

49. }  

The following is the pwm output waveform captured by the logic analyzer: