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本例程出自STM32MED1开发板附带光盘,其工程目录路径为:\Code Package\Peripheral Devices\06 TIM\0603_PWM_Output。
高级定时器TIM1的通道1位于GPIOA.8引脚,此管脚正好与开发板上LED1相连,这样就可以通过观察LED1亮度变化来判断TIM1的PWM输出波形变化情况。
通过调用函数TIM1_PWMOutputConfig()可对TIM1的PWM输出进行配置。其代码定义如下:
void TIM1_PWMOutputConfig(u16 Period)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
GPIO_InitTypeDef GPIO_InitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_TIM1, ENABLE); // 1)
// (2
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
// 2)
// (3
TIM_TimeBaseStructure.TIM_Period = Period;
TIM_TimeBaseStructure.TIM_Prescaler = (u16)(SystemCoreClock / 100000) - 1;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
// 3)
// (4
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_Pulse = 0;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
// 4)
TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Disable); // 5)
TIM_ClearFlag(TIM1, TIM_FLAG_Update); // 6)
TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE); // 7)
TIM_UpdateRequestConfig(TIM1, TIM_UpdateSource_Global); // 8)
// (9
NVIC_InitStructure.NVIC_IRQChannel = TIM1_UP_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
// 9)
TIM_CtrlPWMOutputs(TIM1, ENABLE); // 10)
TIM_Cmd(TIM1, ENABLE); // 11)
}
代码行1)开启GPIOA及TIM1外设的时钟。代码段2)将PA.8管脚配置为复用推挽输出,因此TIM1产生的PWM信号能输出到PA.8管脚。代码段3)是对TIM1的时间基配置。代码段4)配置TIM1的输出比较通道1,将其配置为PWM模式2;起始寄存器TIM1_CCR1的值设为0;开启OC1的输出状态,关闭OC1的互补输出状态。代码行5)关闭OC1通道的预装载功能,使得每次向捕获/比较寄存器中写入的数据立即生效。代码行6)是清除TIM1的更新标志位。代码行7)是开启TIM1的更新中断,代码行8)将更新事件源限制为计时器的上溢或下溢。代码行9)是对TIM1的中断通道进行初始化。代码行10)是开启TIM1的PWM输出。代码行11)是使能TIM1外设。
当TIM1计数器的值达到最大时就会产生更新中断,其中断处理函数定义如下:
void TIM1_UP_IRQHandler(void)
{
if (TIM_GetITStatus(TIM1, TIM_IT_Update) != RESET)
{
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