PWM实验LED亮度无变化求助

2672751679 · 发表于 2016-6-18 14:09:31

//精英板-PWM实验LED0的亮度不会变化，谢谢

//pwm.h
#include "stm32f10x.h"

#ifndef __PWM_H
#define __PWM_H

void PWM_Init(u16 arr,u16 psc);

#endif

//pwm.c
#include "stm32f10x.h"
#include "pwm.h"

void PWM_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB,ENABLE);  //ê1ÄüGPIOBμÄê±Öó
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);  //ê1ÄüAFIO¸′óÃ1|ÄüÄ￡¿éê±Öó
GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3,ENABLE);  //Timer32¿·ÖÖØó3éä  TIM3_CH2->PB5
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;  //PB5Îa¸′óÃíÆíìêä3öÄ￡ê½
GPIO_InitStructure.GPIO_Pin=GPIO_Pin_5;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_Init(GPIOB,&GPIO_InitStructure);

TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up; //TIMÏòéÏ¼ÆêyÄ￡ê½
TIM_TimeBaseInitStructure.TIM_ClockDivision=0;  //éèÖÃê±Öó·Ö¸î:TDTS = Tck_tim
TIM_TimeBaseInitStructure.TIM_Period=arr*10-1;  //×Ô¶ˉÖØ×°ÔØ¼Ä′æÆ÷ÖüÆúμÄÖμ
TIM_TimeBaseInitStructure.TIM_Prescaler=psc-0;  //éèÖÃóÃà′×÷ÎaTIMxê±ÖóÆμÂê3yêyμÄÔ¤·ÖÆμÖμ
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseInitStructure);

TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM2;  //Ñ¡Ôñ¶¨ê±Æ÷Ä￡ê½:TIMÂö3å¿í¶èμ÷ÖÆÄ￡ê½2
TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_High;  //êä3ö¼«DÔ:TIMêä3ö±è½Ï¼«DÔ¸ß
TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;  //±è½Ïêä3öê1Äü
TIM_OC2Init(TIM3,&TIM_OCInitStructure);

TIM_OC2PreloadConfig(TIM3,TIM_OCPreload_Enable);  //ê1ÄüÔ¤×°ÔØ¼Ä′æÆ÷

TIM_Cmd(TIM3,ENABLE);  //ê1ÄüTIM3

}

//main.c
#include "stm32f10x.h"

#include "pwm.h"

int main(void)
{
u32 ccr2=899;  //éèÖÃÕ¼¿Õ±è
u8 a=0;

PWM_Init(900,0);  //2»·ÖÆμ¡￡PWMÆμÂê=72000000/900=80Khz

   while(1)
{
if(ccr2==899) a=1;

   if(a==1)
{
   ccr2--;
   TIM_SetCompare2(TIM3,ccr2);
}

if(ccr2==0) a=2;

if(a==2)
{
   ccr2++;
   TIM_SetCompare2(TIM3,ccr2);
}

}

}