【实验目的】
输出7路占空比不同的PWM信号是各个版本ST库必备的例子。本实验的主要目的不是表现ST芯片PWM功能的强大，而是要完成输出的精确计算。
【实验内容】
输出7路PWM信号，并用示波器测量输出。
【实验原理】
1、时基单元初始化
TIM1和TIM8使用内部时钟时，时钟由APB2提供。但是定时器的时钟并不是直接由APB2提供，而是来自于输入为APB2的一个倍频器。当APB2的与分频系数为1时，这个倍频器不起作用，定时器时钟频率等于APB2时钟。当APB2预分频系数为其他时这个倍频器起作用。定时器的输入频率等于APB2的2倍。本实验中，APB2时钟被设置成了84M是对系统时钟进行2分频。因此定时器的输入时钟是84M×2 = 168M = SYSCLK。（PS：这个倍频我在ST的手册上边没有找到，是网上搜索得到的结果，与实际结果对比是正确的）
TIM_Prescaler 为预分频值，为0时分频系数为1.
TIM_Period 为每个周期计数值，从0开始计数所以其值应为计数次数减去1。
TIM_RepetitionCounter是F4新增的一个东西，只有高级定时器TIM1和TIM8有效，对应寄存器RCR。意思就是每TIM_RepetitionCounter+1个技术周期产生一次中断。
我定义的时基如下，将产生频率为20K的即使基准：
TimerPeriod = (SystemCoreClock / 20000 ) - 1;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1,ENABLE);
//时基初始化
TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1; //死区控制用。
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up; //计数器方向
TIM_TimeBaseInitStructure.TIM_Prescaler = 0; //Timer clock = sysclock /(TIM_Prescaler+1) = 168M
TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInitStructure.TIM_Period = TimerPeriod - 1; //Period = (TIM counter clock / TIM output clock) - 1 = 20K
TIM_TimeBaseInit(TIM1,&TIM_TimeBaseInitStructure);
2、计时输出
ccr1、2、3、4为各个技术周期的TIM_Pulse。即每当计数到这些个值的时候，PWM波形就会反转。
ccr1 = TimerPeriod / 2; //占空比1/2 = 50%
ccr2 = TimerPeriod / 3; //占空比1/3 = 33%
ccr3 = TimerPeriod / 4; //占空比1/4 = 25%
ccr4 = TimerPeriod / 5; //占空比1/5 = 20%
定义输出部分：
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 = ccr1;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;//输出同相，TIM_OCNPolarity_High时输出反相
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;TIM_OC1Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr2;
TIM_OC2Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr3;
TIM_OC3Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr4;
TIM_OC4Init(TIM1,&TIM_OCInitStructure);TIM_Cmd(TIM1,ENABLE);
TIM_CtrlPWMOutputs(TIM1,ENABLE);
3、到这里就完成了定时器的配置，下边是GPIO引脚的配置
使用GPIOE的8、9、10、11、12、13、14引脚进行PWM输出。配置如下：
void TIM1_GPIO_Config(void)
{
//PE 8 9 10 11 12 13 14输出
GPIO_InitTypeDef GPIO_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE,ENABLE);
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11
| GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOE,&GPIO_InitStructure);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource8,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource9,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource10,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource11,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource12,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource13,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource14,GPIO_AF_TIM1);
}
输出波形图：
同相输出时候：
OC1/OC1N
OC2/OC2N
OC3/OC3/N
OC4
反相输出
OC1/OC1N
OC2/OC2N
OC3/OC3/N
OC4
完整的应用代码：
使用时只主要两行即可
//主函数调用
TIM1_GPIO_Config();
Tim1_Config();
//定时器输出引脚初始化
void TIM1_GPIO_Config(void)
{
//PE 8 9 10 11 12 13 14输出
GPIO_InitTypeDef GPIO_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE,ENABLE);
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11
| GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_Init(GPIOE,&GPIO_InitStructure);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource8,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource9,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource10,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource11,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource12,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource13,GPIO_AF_TIM1);
GPIO_PinAFConfig(GPIOE,GPIO_PinSource14,GPIO_AF_TIM1);
}
//TIM1做PWM输出
void Tim1_Config(void)
{
TimerPeriod = (SystemCoreClock / 20000 ) - 1;
ccr1 = TimerPeriod / 2; //占空比1/2 = 50%
ccr2 = TimerPeriod / 3; //占空比1/3 = 33%
ccr3 = TimerPeriod / 4; //占空比1/4 = 25%
ccr4 = TimerPeriod / 5; //占空比1/5 = 20%
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1,ENABLE);
//时基初始化
TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1; //死区控制用。
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up; //计数器方向
TIM_TimeBaseInitStructure.TIM_Prescaler = 0; //Timer clock = sysclock /(TIM_Prescaler+1) = 168M
TIM_TimeBaseInitStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInitStructure.TIM_Period = TimerPeriod - 1; //Period = (TIM counter clock / TIM output clock) - 1 = 20K
TIM_TimeBaseInit(TIM1,&TIM_TimeBaseInitStructure);
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 = ccr1;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;
TIM_OC1Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr2;
TIM_OC2Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr3;
TIM_OC3Init(TIM1,&TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = ccr4;
TIM_OC4Init(TIM1,&TIM_OCInitStructure);
TIM_Cmd(TIM1,ENABLE);
TIM_CtrlPWMOutputs(TIM1,ENABLE);
}
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