PWM breathing lamp

Mission ：

1. Learn timer output PWM, Realization PWM Breathing lights
2. understand PWM Principle of breathing lamp

And pwm Knowledge points about controlling breathing lights

The previous one used the delay function to control the steering gear , The delay function will occupy the MCU cup, inefficiency

pwm Pulse width modulator （ Duty cycle ）： Control the high and low level
Use the digital output of microprocessor to control the analog circuit

High level LED Lighten up , Low level LED Extinguish
The length of the high level determines LED The brightness of

There should be a complete cycle , The length of high and low levels changes constantly , Cycle length （ frequency ） unchanged , A cycle appears repeatedly

pwm May by stm32 Timer generation in , Advanced timer TIM1, Ordinary timer TIM2,TIM3,TIM4





ccrx Indicates the change position of high and low levels in a cycle
ccrx Adjust the high level up to reduce the column , Adjust the high-level ratio downward to increase


 
It can make LED1 or LED2 bright , But two cannot light at the same time

Complete code ：

main.c

int main(void)
{
    
u16 t = 500;
u8 dir = 1;
//delay_init();
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
//uart_init(115200);
LED_Init();
TIM3_PWM_Init(59999,23);

while(1)
{
    
delay_ms(10);
if(dir)t=t+400;
 else t=t-400;

if(t>60000)dir = 0;

if(t==500)dir = 1;

// TIM_SetCompare3(TIM3,t);
 TIM_SetCompare4(TIM3,t);

pwm.c

void TIM3_PWM_Init(u16 arr,u16 psc){
      //TIM3 PWM initialization  arr Reload value  psc The prescaled coefficients 
    GPIO_InitTypeDef     GPIO_InitStrue;
    TIM_OCInitTypeDef     TIM_OCInitStrue;
    TIM_TimeBaseInitTypeDef     TIM_TimeBaseInitStrue;
    
    
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);// Can make TIM3 And the related GPIO The clock 
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);// Can make GPIOB The clock (LED stay PB0 Pin )
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);// Can make AFIO The clock ( Timer 3 passageway 3 Need to remap to BP5 Pin )
    
// GPIO_InitStrue.GPIO_Pin=GPIO_Pin_0; // TIM_CH3
	GPIO_InitStrue.GPIO_Pin=GPIO_Pin_1;     // TIM_CH4
    GPIO_InitStrue.GPIO_Mode=GPIO_Mode_AF_PP;    //  Reuse push pull 
    GPIO_InitStrue.GPIO_Speed=GPIO_Speed_50MHz;    // Set the maximum output speed 
    GPIO_Init(GPIOB,&GPIO_InitStrue);                //GPIO Port initialization settings 
    
// GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3,ENABLE); // mapping , Remapping is only used for 64、100、144 Single chip microcomputer foot 
   // When there is no remapping ,TIM3 The four channels of CH1,CH2,CH3,CH4 They correspond to each other PA6,PA7,PB0,PB1
   // When partially remapped ,TIM3 The four channels of CH1,CH2,CH3,CH4 They correspond to each other PB4,PB5,PB0,PB1 (GPIO_PartialRemap_TIM3)
   // When completely remapped ,TIM3 The four channels of CH1,CH2,CH3,CH4 They correspond to each other PC6,PC7,PC8,PC9 (GPIO_FullRemap_TIM3) 
	      
    TIM_TimeBaseInitStrue.TIM_Period=arr;    // Set auto reload load value 
    TIM_TimeBaseInitStrue.TIM_Prescaler=psc;        // The prescaled coefficients 
    TIM_TimeBaseInitStrue.TIM_CounterMode=TIM_CounterMode_Up;    // The counter overflows up 
    TIM_TimeBaseInitStrue.TIM_ClockDivision=TIM_CKD_DIV1;        // The division factor of the clock , It plays a little delay role , General set to TIM_CKD_DIV1
    TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStrue);        //TIM3 Initialize settings ( Set up PWM The cycle of )
    
    TIM_OCInitStrue.TIM_OCMode=TIM_OCMode_PWM1;        // PWM Pattern 1:CNT < CCR Output effective level at 
//TIM_OCInitStrue.TIM_OCMode=TIM_OCMode_PWM2;
	TIM_OCInitStrue.TIM_OCPolarity=TIM_OCPolarity_High;//  Set polarity - The effective level is ： High level 
    TIM_OCInitStrue.TIM_OutputState=TIM_OutputState_Enable;//  Output enable 
//
//TIM_OC3Init(TIM3,&TIM_OCInitStrue); //TIM3 The passage of 3 PWM  Mode setting 
//
// TIM_OC3PreloadConfig(TIM3,TIM_OCPreload_Enable);


    TIM_OC4Init(TIM3,&TIM_OCInitStrue);        //TIM3 The passage of 4 PWM  Mode setting 

    TIM_OC4PreloadConfig(TIM3,TIM_OCPreload_Enable);        // Enable preload register 
    


    TIM_Cmd(TIM3,ENABLE);        // Can make TIM3
    
}

Be careful ： PWM clock frequency =72000000/(59999+1)*(23+1) = 50HZ (20ms),
Set up Auto load values 60000,
prescale coefficient 24