前言

本文简单介绍了PWM定时器生成与通道输出的关系。

PWM_16">一、PWM通道与定时器的关系

1.简介

PWM（脉宽调制） 通过周期性的高低电平切换产生可变占空比的信号࿰c;广泛应用于电机控制、LED调光等领域。其核心依赖**定时器（Timer）**模块生成精确的时间基准࿰c;具体关系如下：

PWM_20">2.定时器作为PWM的时基发生器

定时器通过内部计数器周期性递增/递减࿰c;生成固定频率的时钟信号。计数器的溢出频率决定了PWM信号的频率。

PWM_23">3.通道作为PWM的输出接口

每个定时器通常有多个通道（如STM32的TIM1有4个通道）࿰c;每个通道可独立输出PWM信号。通过配置通道的比较寄存器（CCR）࿰c;可调整占空比。

4.协同工作流程

5.关键公式

PWM_37">二、输出PWM的设置步骤（通用流程）

以下步骤以STM32为例࿰c;但原理适用于多数微控制器：

1. 选择定时器与通道

根据硬件设计࿰c;选择支持PWM输出的定时器及对应通道（如TIM3_CH1对应PB4引脚）。

2. 配置时钟源

<code class="prism language-c">class="token comment">// 使能定时器时钟（以STM32为例）
class="token function">RCC_APB1PeriphClockCmdclass="token punctuation">(RCC_APB1Periph_TIM3class="token punctuation">, ENABLEclass="token punctuation">)class="token punctuation">;
code>

3. 初始化定时器参数

预分频器

自动重装载

<code class="prism language-c">TIM_TimeBaseInitTypeDef TIM_TimeBaseStructclass="token punctuation">;
TIM_TimeBaseStructclass="token punctuation">.TIM_Prescaler class="token operator">= class="token number">71class="token punctuation">;          class="token comment">// 72MHz/(71+1)=1MHz
TIM_TimeBaseStructclass="token punctuation">.TIM_CounterMode class="token operator">= TIM_CounterMode_Upclass="token punctuation">;
TIM_TimeBaseStructclass="token punctuation">.TIM_Period class="token operator">= class="token number">999class="token punctuation">;            class="token comment">// PWM频率=1MHz/(999+1)=1kHz
class="token function">TIM_TimeBaseInitclass="token punctuation">(TIM3class="token punctuation">, class="token operator">&TIM_TimeBaseStructclass="token punctuation">)class="token punctuation">;
code>

PWM_64">4. 配置PWM模式

<code class="prism language-c">TIM_OCInitTypeDef TIM_OCStructclass="token punctuation">;
TIM_OCStructclass="token punctuation">.TIM_OCMode class="token operator">= TIM_OCMode_PWM1class="token punctuation">;      class="token comment">// PWM模式1（CNT < CCR时输出有效电平）
TIM_OCStructclass="token punctuation">.TIM_OutputState class="token operator">= TIM_OutputState_Enableclass="token punctuation">;
TIM_OCStructclass="token punctuation">.TIM_Pulse class="token operator">= class="token number">500class="token punctuation">;                   class="token comment">// 初始占空比50%（CCR=500）
TIM_OCStructclass="token punctuation">.TIM_OCPolarity class="token operator">= TIM_OCPolarity_Highclass="token punctuation">; class="token comment">// 高电平有效
class="token function">TIM_OC1Initclass="token punctuation">(TIM3class="token punctuation">, class="token operator">&TIM_OCStructclass="token punctuation">)class="token punctuation">;               class="token comment">// 初始化通道1
code>

5. 配置GPIO为复用功能

<code class="prism language-c">GPIO_InitTypeDef GPIO_InitStructclass="token punctuation">;
GPIO_InitStructclass="token punctuation">.GPIO_Pin class="token operator">= GPIO_Pin_4class="token punctuation">;
GPIO_InitStructclass="token punctuation">.GPIO_Mode class="token operator">= GPIO_Mode_AF_PPclass="token punctuation">;    class="token comment">// 复用推挽输出
GPIO_InitStructclass="token punctuation">.GPIO_Speed class="token operator">= GPIO_Speed_50MHzclass="token punctuation">;
class="token function">GPIO_Initclass="token punctuation">(GPIOBclass="token punctuation">, class="token operator">&GPIO_InitStructclass="token punctuation">)class="token punctuation">;
code>

6. 启动定时器与通道

<code class="prism language-c">class="token function">TIM_Cmdclass="token punctuation">(TIM3class="token punctuation">, ENABLEclass="token punctuation">)class="token punctuation">;          class="token comment">// 启动定时器
class="token function">TIM_CtrlPWMOutputsclass="token punctuation">(TIM3class="token punctuation">, ENABLEclass="token punctuation">)class="token punctuation">; class="token comment">// 若为高级定时器（如TIM1）࿰c;需额外使能主输出
code>

7. 动态调整占空比

<code class="prism language-c">class="token function">TIM_SetCompare1class="token punctuation">(TIM3class="token punctuation">, new_CCRclass="token punctuation">)class="token punctuation">;  class="token comment">// 修改通道1的CCR值以改变占空比
code>

8.关键注意事项

频率与分辨率的权衡

中央对齐模式

死区电压

9.示例应用：呼吸灯

<code class="prism language-c">class="token comment">// 在循环中逐渐改变CCR值
class="token keyword">forclass="token punctuation">(class="token class-name">uint16_t iclass="token operator">=class="token number">0class="token punctuation">; iclass="token operator"><=class="token number">1000class="token punctuation">; iclass="token operator">+=class="token number">10class="token punctuation">) class="token punctuation">{class="token function">TIM_SetCompare1class="token punctuation">(TIM3class="token punctuation">, iclass="token punctuation">)class="token punctuation">;class="token function">Delay_msclass="token punctuation">(class="token number">10class="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>

通过以上步骤࿰c;定时器与PWM通道协同工作࿰c;实现了灵活的信号输出控制。实际开发中需参考具体芯片的数据手册࿰c;确保寄存器和库函数正确配置。