The principle, use and configuration of PWM peripherals in STM32

As for what PWM is, just search on Baidu. In fact, the content is simple. First of all, the PWM function in STM32 is implemented using a counter, which is similar to 51, but there are also differences. 51 uses the interrupt of the counter to adjust the duty cycle, which takes up the time of the MCU. However, STM32 uses hardware to implement the PWM function, so PWM is a peripheral function. (The counter's up-counting, down-counting, and center-aligned modes are not introduced).

PWM mainly configures 2 registers. TIMx_ARR = T (set period T, frequency setting)

     TIMx_CCRx = t (set duty cycle, this is a library function)

**P.S.: PWM still enters the interrupt operation of the connected TIMx. However, the 51 interrupt is interrupted as a small part and then counts to perform pwm modulation. However, STM32 enters when it reaches ti and has already been modulated.

  #include "PWM.h"

void PWM_init()
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;  
GPIO_InitTypeDef GPIO_InitStructure;              
TIM_OCInitTypeDef TIM_OCInitStructure;             

//Hook up the clock RCC

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC,ENABLE);  
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);  

/* Timer configuration */

TIM_TimeBaseStructure.TIM_Period = 900 ; //Set timer frequency           
TIM_TimeBaseStructure.TIM_Prescaler = 0; //No frequency division 
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //Count up    
TIM_TimeBaseInit(TIM3, & TIM_TimeBaseStructure); 

TIM_Cmd(TIM3, ENABLE);                          

/* PWM configuration*/
TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;   
TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_Low;      
TIM_OC2Init(TIM3, &TIM_OCInitStructure);                   
TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);           

GPIO_PinRemapConfig(GPIO_FullRemap_TIM3, ENABLE); //Specify the mapping of the pin, this configured pwm is mapped to TIM3 

/* Configure pwm to adjust the brightness of the led, so configure the GPIO of the led*/
GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz; 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;        
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //Push-pull multiplexing function, pwm controls the led, if it is not an MCU, GPIO_Mode_Out_PP is not used
GPIO_Init(GPIOC,&GPIO_InitStructure);            

}

Functions used in interrupt files

void EXTI2_IRQHandler(void) //Here the external interrupt is used as the ti (duty cycle) of modulated pwm
{
if(EXTI_GetITStatus(EXTI_Line2)==SET) //Judge whether to enter external interrupt 2
{
EXTI_ClearITPendingBit(EXTI_Line2); // Clear the suspension of line EXIT
delay_ms(10); //
if(GPIO_ReadInputDataBit(GPIOE,GPIO_Pin_2)==Bit_RESET) //Read whether key_up is pressed
{
if(ti<500)
ti=ti+100;
else 
ti=0; //Press the button to increase the duty cycle
 }
while(GPIO_ReadInputDataBit(GPIOE,GPIO_Pin_2)==0); //Yes, here is the release judgment
}
}


void TIM3_IRQHandler(void) //When ti is reached, enter the interrupt and give the led a high level with a certain duty cycle
{
static u8 i=0;
       TIM_ClearITPendingBit(TIM3,TIM_IT_Update); //Clear the interrupt source
GPIO_Write(GPIOC,(u16)~(0x01<if(i==8) i=0;
}

main.c The main function is simple

#include "public.h"
#include "Systick.h"
#include "PWM.h"
#include "ExInter.h"

int main()

{

PWM_init();
ExInter_init();
 while(1)
{
delay_ms(10);
TIM_SetCompare2(TIM3,ti); //Connect channel 2,
}  

}

To be honest, it is a good habit to write down your understanding in comments.