PWM output experiment

One 、 Universal timer PWM summary

STM32 PWM working process

Input comparison register （CCRx） Save a value in , During counter counting , Same as CCRx Value comparison , Greater than （ Or less than ） Low potential will be generated , On the contrary, high potential is generated . The timer cycle counts to produce PWM wave , Its period is determined by ARR Values determine , The duty cycle is proportional to the period ratio of high-level duration （ from CCRx decision ）

STM32 working process （ passageway 1 For example ）

1、 Counter CNT The value of will be equal to CCR1 Value comparison , If CNT Greater than CCR1 A high level signal will be generated .

2、CCMR1 There are two bits , about PWM Under way , Used for setting up PWM Pattern 1 or PWM Pattern 2（ The value ratio of the counter CCRx The value of is smaller than the effective level ）

Pattern 1 With the model 2 The difference between ：

3、 After comparison, it will be selected through the selector , choice 0 or 1 from CCER：CC1P Bit decided .（CCER：CC1P position ： Input / Capture 1 Output polarity .0： High active ,1： Low level active .）

4、 The signal reaches the output enable circuit , adopt CCER：CC1E Bit enable （CCER：CC1E position ： Input / Capture 1 Output enable .0： close ,1： open .） Thus, the signal is output to the corresponding pin .

（ First of all PWM The mode determines the effective level , Let's see whether the effective level is high or low ）

Take the up count configuration as an example

As you can see from the picture

Counter register ARR Count to 8 Count again when ,CCRx Set to 4 Then count to 0123 High level （ It works ）, by 45678 Low when （ Invalid ）;CCRx Set to 8 be 0~7 When it is low, otherwise it is high .CCRx It can't be compared with ARR Otherwise, it cannot be produced PWM wave form .

ARPE=0, With cache , Effective next cycle , Count to F5 There will be an update event .ARPE=1,ARR Immediate effect .

Two 、PWM Output library function

void TIM_OCxInit(TIM_TypeDef* TIMx,TIM_OCInitTypeDef* TIM_OCInitStruct);
typedef struct
{
  uint16_t TIM_OCMode;//PWM Pattern 1 or 2
  uint16_t TIM_OutputState;// Output enable OR
  uint16_t TIM_OutputNState;
  uint16_t TIM_Pulse;// It's worth , Write CRRx
  uint16_t TIM_OCPolarity;// Compare the output polarity 
  uint16_t TIM_OCNPolarity;
  uint16_t TIM_OCldleState;
  uint16_t TIM_OCNldleState;
}
  TIM_OCInitTypeDef;

  TIM_OCInitABC.TIM_OCMode=TIM_OCMode_PWM2;//PWM Pattern 2
  TIM_OCInitABC.TIM_OutputState=TIM_OutputState_Enable;// Compare output enable 
  TIM_OCInitABC.TIM_Pulse=100;
  TIM_OCInitABC.TIM_OCPolarity=TIM_OCPolarity_High;// Output polarity ：TIM High output polarity 
  TIM_OC2Init(TIM3,&TIM_InitABC);// according to T The specified parameter initializes the peripheral TIM3 OC2

Set the comparison value function ：void TIM_SetCompareX(TIM_TypeDef* TIMx,uint16_t Comparex);

Enable output comparison preload ：

void TIMx_OCxPreloadComfig(TIM_TypeDef* TIMx,uint16_t TIMOCPreload);

The preload register that enables automatic reload allows bits ：

void TIM_ARRPreloadConfig(TIM_TypeDef* TIMx,FunctionalState NewState);

3、 ... and 、 Write a PWM Output experiment

requirement ： Use timer 14 Of PWM function , The output frequency is variable PWM wave , To drive LED The lamp , So as to achieve LED【PF9】 The brightness changes from dark to bright , And the process from light to dark , And cycle .

PWM Output configuration steps ：

1、 Enable timer 14 And the related IO Port clock .

      Enable timer 14 The clock ：RCC_APB1PeriphClockCmd();

      Can make GPIOF The clock ：RCC_AHB1PeriphClockCmd();

2、 initialization IO The port is a multiplexing function output function ：

GPIO_Init();   GPIO_InitABC.GPIO_Mode=GPIO_Mode_AF;// Reuse function

3、GPIOF9 Multiplexing maps to timers 14

GPIO_PinAFConfig(GPIOF,GPIO_PinSource9,GPIO_AF_TIM14);

4、 Initialize the timer ：ARR、PSC etc. ：TIM_TimeBaseInit();

5、 Initialize the output comparison parameters ：TIM_OC1Init();

6、 Enable preload register ：TIM_OC1PreloadConfig(TIM14,TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM14,ENABLE);

7、 Enable timer .

8、 Constantly changing the comparison value CCRx, Achieve different duty cycle effects ：TIM_SetCompare1();

#include "pwm.h"
void TIM14_PWM_Init(u32 arr,u32 psc)
{
	GPIO_InitTypeDef GPIO_InitABC;// Structure 
	TIM_TimeBaseInitTypeDef TIM_TimeBaseInitABC;
	TIM_OCInitTypeDef TIM_OCInitABC;
	
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM14,ENABLE);// Can make TIM14 The clock 
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOF,ENABLE);
  
	GPIO_InitABC.GPIO_Mode=GPIO_Mode_AF;// Reuse 
	GPIO_InitABC.GPIO_OType=GPIO_OType_PP;// Push pull multiplex output 
	GPIO_InitABC.GPIO_Pin=GPIO_Pin_9;//GPIOF9
	GPIO_InitABC.GPIO_PuPd=GPIO_PuPd_UP;// Pull up 
	GPIO_InitABC.GPIO_Speed=GPIO_Speed_100MHz;// Speed 100Hz
	GPIO_Init(GPIOF,&GPIO_InitABC);// initialization PF9
	
	GPIO_PinAFConfig(GPIOF,GPIO_PinSource9,GPIO_AF_TIM14);
  
	TIM_TimeBaseInitABC.TIM_ClockDivision=TIM_CKD_DIV1;
	TIM_TimeBaseInitABC.TIM_CounterMode=TIM_CounterMode_Up;// Upcount mode 
	TIM_TimeBaseInitABC.TIM_Period=arr;// Automatic reload load value 
	TIM_TimeBaseInitABC.TIM_Prescaler=psc;// Timer frequency division 
	
	TIM_TimeBaseInit(TIM14,&TIM_TimeBaseInitABC);// Initialize the timer TIM14
	
	TIM_OCInitABC.TIM_OCMode=TIM_OCMode_PWM1;//PWM Pattern 1
	TIM_OCInitABC.TIM_OCPolarity=TIM_OCPolarity_Low;// The active level is low 
	TIM_OCInitABC.TIM_OutputState=TIM_OutputState_Enable;
	
	TIM_OC1Init(TIM14,&TIM_OCInitABC);
	
	TIM_OC1PreloadConfig(TIM14,TIM_OCPreload_Enable);
	TIM_ARRPreloadConfig(TIM14,ENABLE);
	
	TIM_Cmd(TIM14,ENABLE);//
	
}
int main(void)
{ 
  u16 led0=0;
  u8 dir=1;
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);// Set system interrupt priority group 2
	delay_init(168);// Initialization delay function 
	uart_init(115200);// Initialize the serial port baud rate to 115200
	TIM14_PWM_Init(500-1,84-1);
//84M/84=1Mhz The counting frequency of , Reload value 500, therefore PWM The frequency is 1M/500=2Khz
	while(1)
	{
	delay_ms(100);
	if(dir) led0++;// Increasing 
	else led0--;// Decline 
	if(led0>300) dir=0;// arrive 300 after , The direction is decreasing 
	if(led0==0) dir=1;// Descending to 0 after , Change the direction to incremental 
	
	TIM_SetCompare1(TIM14,led0);// Modify the comparison value , Change the duty cycle 
	}
}