STM32MED1开发板例程解析（二）：定时器的PWM输出

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Cody-2045860 发布时间：2013-10-15 15:40

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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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