PWM基本概念
PWM（脈沖寬度調制）是一種通過快速開關數字信號來控制模擬電路的技術，通過改變脈沖的占空比來控制平均電壓。STM32F407的定時器外設可以生成PWM信號。
STM32F407 PWM配置步驟
1. 定時器時鐘使能
首先需要使能定時器的時鐘：
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); // 對于TIM3
// 或者
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE); // 對于高級定時器如TIM1
2. GPIO配置
配置用于PWM輸出的GPIO引腳：
GPIO_InitTypeDef GPIO_InitStructure;GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6; // 例如TIM3_CH1在PC6
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOC, &GPIO_InitStructure);// 配置引腳復用功能
GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);
3. 定時器基本配置
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;TIM_TimeBaseStructure.TIM_Period = 8399; // 自動重裝載值
TIM_TimeBaseStructure.TIM_Prescaler = 0; // 預分頻器
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
4. PWM輸出通道配置
TIM_OCInitTypeDef TIM_OCInitStructure;TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 0; // 初始占空比
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);
5. 使能定時器
TIM_ARRPreloadConfig(TIM3, ENABLE); // 使能ARR預裝載
TIM_Cmd(TIM3, ENABLE); // 使能定時器// 對于高級定時器（如TIM1）還需要以下代碼
TIM_CtrlPWMOutputs(TIM1, ENABLE);
PWM頻率和占空比計算
PWM頻率計算
PWM頻率由以下公式決定：
PWM頻率 = 定時器時鐘頻率 / ((Prescaler + 1) * (Period + 1))
例如，對于84MHz時鐘，Prescaler=0，Period=8399：
PWM頻率 = 84,000,000 / (1 * 8400) = 10,000 Hz (10kHz)
占空比設置
占空比通過改變TIM_Pulse值來設置：
占空比 = (TIM_Pulse + 1) / (Period + 1)
例如，要設置50%占空比：
TIM_SetCompare1(TIM3, 4199); // (8400 / 2) - 1
PWM應用示例
控制LED亮度
void PWM_LED_Init(void)
{// 初始化代碼如上...// 設置PWM頻率為1kHzTIM_TimeBaseStructure.TIM_Period = 83999; // 84MHz/84000 = 1kHzTIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);// 初始占空比50%TIM_SetCompare1(TIM3, 41999);
}// 改變亮度
void Set_LED_Brightness(uint8_t brightness) // brightness: 0-100
{uint32_t pulse = (brightness * 83999) / 100;TIM_SetCompare1(TIM3, pulse);
}
控制電機速度
void PWM_Motor_Init(void)
{// 初始化代碼...// 設置PWM頻率為20kHzTIM_TimeBaseStructure.TIM_Period = 4199; // 84MHz/4200 = 20kHzTIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);// 初始速度為0TIM_SetCompare1(TIM3, 0);
}void Set_Motor_Speed(uint8_t speed) // speed: 0-100
{uint32_t pulse = (speed * 4199) / 100;TIM_SetCompare1(TIM3, pulse);
}
使用HAL庫配置PWM
// 1. 定時器句柄聲明
TIM_HandleTypeDef htim3;
TIM_OC_InitTypeDef sConfigOC;// 2. 定時器基本配置
htim3.Instance = TIM3;
htim3.Init.Prescaler = 0;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 8399;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
HAL_TIM_PWM_Init(&htim3);// 3. PWM通道配置
sConfigOC.OCMode = TIM_OCMODE_PWM1;
sConfigOC.Pulse = 0;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1);// 4. 啟動PWM
HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1);// 改變占空比
__HAL_TIM_SET_COMPARE(&htim3, TIM_CHANNEL_1, 4200); // 設置50%占空比
高級應用技巧
互補PWM輸出（用于電機驅動）
// 配置主輸出
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_Pulse = 0;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);// 使能死區時間
TIM_BDTRInitTypeDef TIM_BDTRInitStructure;
TIM_BDTRInitStructure.TIM_OSSRState = TIM_OSSRState_Enable;
TIM_BDTRInitStructure.TIM_OSSIState = TIM_OSSIState_Enable;
TIM_BDTRInitStructure.TIM_LOCKLevel = TIM_LOCKLevel_1;
TIM_BDTRInitStructure.TIM_DeadTime = 0x54; // 設置死區時間
TIM_BDTRInitStructure.TIM_Break = TIM_Break_Enable;
TIM_BDTRInitStructure.TIM_BreakPolarity = TIM_BreakPolarity_High;
TIM_BDTRInitStructure.TIM_AutomaticOutput = TIM_AutomaticOutput_Enable;
TIM_BDTRConfig(TIM1, &TIM_BDTRInitStructure);TIM_CtrlPWMOutputs(TIM1, ENABLE);
多通道PWM同步
// 配置多個通道
TIM_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC2Init(TIM3, &TIM_OCInitStructure);
TIM_OC3Init(TIM3, &TIM_OCInitStructure);// 使用主從模式同步多個定時器
TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable);
TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update);
調試技巧
- 使用示波器檢查PWM波形是否符合預期
- 檢查時鐘配置是否正確
- 確保GPIO引腳復用功能配置正確
- 驗證預分頻器和自動重裝載值計算是否正確
- 檢查是否有其他外設沖突使用同一定時器
通過以上步驟和示例，您可以在STM32F407上成功配置和應用PWM功能。
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