[嵌入式]22. PWM输出实验

通用定时器PWM概述

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常用寄存器和库函数配置

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手把手写PWM输出实验

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#ifndef __PWM_H
#define __PWM_H
#include "sys.h"

void TIM14_PWM_Init(u32 arr, u32 crr);

#endif

#include "stm32f4xx.h"
#include "pwm.h"

void TIM14_PWM_Init(u32 arr, u32 psc)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
	TIM_OCInitTypeDef TIM_OCInitStructure;
	
	// 初始化时钟
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM14,ENABLE);
	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOF,ENABLE);
	
	// 初始化IO口 复用功能输出
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
	GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
	GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
	GPIO_Init(GPIOF,&GPIO_InitStructure);
	
	// PF9复用映射到TIM14
	GPIO_PinAFConfig(GPIOF,GPIO_PinSource9,GPIO_AF_TIM14);
	
	// 初始化定时器
	TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
	TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
	TIM_TimeBaseInitStructure.TIM_Period = arr;
	TIM_TimeBaseInitStructure.TIM_Prescaler = psc;
	TIM_TimeBaseInit(TIM14,&TIM_TimeBaseInitStructure);
	
	// 初始化输入比较参数
	TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
	TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
	TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
	TIM_OC1Init(TIM14,&TIM_OCInitStructure);
	
	// 使能预装载寄存器
	TIM_OC1PreloadConfig(TIM14,TIM_OCPreload_Enable);
	TIM_ARRPreloadConfig(TIM14,ENABLE);
	
	// 使能定时器
	TIM_Cmd(TIM14,ENABLE);
	
}

#include "stm32f4xx.h"
#include "led.h"
#include "delay.h"
#include "pwm.h"

int main(void)
{
	u16 led0pwmval = 0;
	u8 dir = 1;
	delay_init(168);
	LED_Init();
	
	//84M/84=1MHz的计数频率，重装载值500，所以PWM频率为1M/500=2kHz
	TIM14_PWM_Init(500-1,84-1); 
	while(1)
	{
		delay_ms(10);
		if(dir)led0pwmval++; // dir==1 led0pwmval递增
		else led0pwmval--; // dir==1 led0pwmval递减
		if(led0pwmval > 300)dir = 0; //led0pwmval达到300，递减
		if(led0pwmval== 0)dir=1; //led0pwmval到0，递增
		
		//修改比较值，占空比
		TIM_SetCompare1(TIM14,led0pwmval);
	}
}