STM32F103RB普通io口模拟pwm输出的第三种方法(周期占空比可调)
- 第(一)种
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- 第(二)种
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- 第(三)种
- 系统滴答定时器(这里和第一种原理一样,不作讲解)
- 完整工程下载>>[GitHub](https://github.com/HDJ1839822/Github.git)
第(一)种
定时器中断产生pwm
io口如何产生一个pwm???,无非就是做一个高低电平周期性的变化,这种思想很重要,确定频率就可以确定周期(T=1/f)也就是在一个周期内产生pwm的时间可以确定下来了,如何改变占空比???确定了时间,高电平的时间不就是想要的占空比么,比如要产生一个频率1khz,占空比为70%的pwm,根据频率我们知道了周期为1ms,产生一个占空比为70%的不就是0.7ms的时间给高电平么,(我们用定时器中断的方式,使0.1ms产生一次中断,计数中断次数,中断处理函数前七次中断都给高电平就ok了)
第(一)种代码片
#include "stdio.h"
#include "usart.h"
#include "tim.h"
#include "led.h"
#include "misc.h"
void TIM2_NVIC(void);
void TIM2_Init(void);
unsigned char ucLed;
unsigned char ucLCK;
int main(void)
{
SysTick_Config(72000);
TIM2_Init();
TIM2_NVIC();
LED_Init();
while(1)
{
LED_Disp(ucLed);
}
}
unsigned int count=0;
unsigned int i;
void TIM2_IRQHandler(void)
{ count++;
if(TIM_GetITStatus(TIM2,TIM_IT_Update) != RESET)
{
if(count%10<i)
ucLed =0xff;
else
ucLed =0;
TIM_ClearITPendingBit(TIM2,TIM_IT_Update);
}
}
void TIM2_NVIC(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
void TIM2_Init(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
TIM_TimeBaseInitStruct.TIM_Prescaler = (2-1);
TIM_TimeBaseInitStruct.TIM_Period = (36000/10)-1;
TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStruct);
TIM_ClearFlag(TIM2,TIM_FLAG_Update);
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);
TIM_Cmd(TIM2, ENABLE);
}
void SysTick_Handler(void)
{
if(ucLCK++%500==0)
{
i++;
if(i==10)
i=0;
}
}
这里的i 是改变占空比的,设置为变量是让pwm增大减小循环,达到呼吸灯的效果,在定时器里面给i做了延时,是为了让它变化得不那么快,让实验现象更加明显
第(二)种
比较匹配+溢出中断
第(二)种代码片
#include "stdio.h"
#include "led.h"
#include "misc.h"
void TIM2_Config(uint16_t duty2);
unsigned char ucLed;
unsigned int Compare2=100;
unsigned int ulTick;
int main(void)
{
SysTick_Config(72000);
TIM2_Config(999/4);
TIM_SetCompare2(TIM2,Compare2);
LED_Init();
while(1)
{
if(ulTick%1000==0)
{
Compare2+=50;
if(Compare2>999)
Compare2=100;
TIM_SetCompare2(TIM2,Compare2);
}
}
}
void TIM2_Config(uint16_t duty1)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
TIM_TimeBaseStructure.TIM_Period = 999;
TIM_TimeBaseStructure.TIM_Prescaler = 71;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
TIM_ClearFlag(TIM2,TIM_FLAG_Update);
TIM_ITConfig(TIM2,TIM_IT_Update|TIM_IT_CC2,ENABLE);
TIM_PrescalerConfig(TIM2,71, TIM_PSCReloadMode_Immediate);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Disable;
TIM_OCInitStructure.TIM_Pulse = duty1;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
TIM_OC2Init(TIM2, &TIM_OCInitStructure);
TIM_OC2PreloadConfig(TIM2,TIM_OCPreload_Enable);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM_Cmd(TIM2, ENABLE);
}
void TIM2_IRQHandler(void)
{
if(TIM_GetITStatus(TIM2,TIM_IT_Update) != RESET)
{
ucLed = 0x00;
LED_Disp(ucLed);
TIM_ClearITPendingBit(TIM2,TIM_IT_Update);
}
else if(TIM_GetITStatus(TIM2,TIM_IT_CC2) != RESET)
{
ucLed = 0xff;
LED_Disp(ucLed);
TIM_ClearITPendingBit(TIM2,TIM_IT_CC2);
}
}
void SysTick_Handler(void)
{
ulTick++;
}
while循环里面也是为了改变占空比,达到呼吸灯的效果
第(三)种
系统滴答定时器(这里和第一种原理一样,不作讲解)
完整工程下载>>GitHub
选择第6个工程(两种方法都在里面)
作者:江多多(在校学生)
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