STM32F103ZET6 用定时器级联方式输出特定数目的PWM

STM32F103ZET6里共有8个定时器，其中高级定时器有TIM1-TIM5、TIM8，共6个。

这里需要使用定时器的级联功能，ST的RM0008 REV12的P388和P399页上有说明对于特定的定时器，怎么去选择级联功能，参见表86。

我这里输出PWM的定时器是TIM2，空闲的定时器是TIM3。以TIM2为主定时器，TIM3为从定时器对TIM2的输出脉冲数进行计数。

查表可知，TIM3为从定时器选择TIM2为触发源，需要配置TS=001，即选择ITR1。

实现通过定时器控制输出PWM个数的功能，可以有如下一种配置方式：

void TIM2_Master__TIM3_Slave_Configuration(u32 PulseFrequency)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef       TIM_OCInitStructure;

    u16 nPDTemp ;
    /* -----------------------------------------------------------------------
    TIMx Configuration: generate 4 PWM signals with 4 different duty cycles:
    TIMxCLK = 72 MHz, Prescaler = 0x0, TIMx counter clock = 72 MHz
    TIMx ARR Register = 0 => TIMx Frequency = TIMx counter clock/(ARR + 1)
    TIMx Frequency = 72MHz.
    ----------------------------------------------------------------------- */
    TIM_Cmd(TIM2, DISABLE);
    nPDTemp = 72000000UL/PulseFrequency;    

// 时基配置：配置PWM输出定时器——TIM2
    /* Time base configuration */
    TIM_TimeBaseStructure.TIM_Period          = nPDTemp-1;
    TIM_TimeBaseStructure.TIM_Prescaler       = 0;
    TIM_TimeBaseStructure.TIM_ClockDivision   = 0;
    TIM_TimeBaseStructure.TIM_CounterMode     = TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    
// 输出配置：配置PWM输出定时器——TIM2
    /* PWM1 Mode configuration: Channel1 */
    TIM_OCInitStructure.TIM_OCMode            = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OCPolarity        = TIM_OCPolarity_High;    
    TIM_OCInitStructure.TIM_OutputState       = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse             = nPDTemp>>1;//50%

    TIM_OC1Init(TIM2, &TIM_OCInitStructure);
    TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);
    
// 时基配置：配置脉冲计数寄存器——TIM3
    TIM_TimeBaseStructure.TIM_Period        = 0xFFFF;
    TIM_TimeBaseStructure.TIM_Prescaler     = 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode   = TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);    
    
    /* Output Compare Active Mode configuration: Channel1 */
    TIM_OCInitStructure.TIM_OCMode                        = TIM_OCMode_Inactive;
    TIM_OCInitStructure.TIM_OCPolarity                = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_OutputState                = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse                        = 0xFFFF; // 这里的配置值意义不大
    
    TIM_OC1Init(TIM3, &TIM_OCInitStructure);
    
// 配置TIM2为主定时器
    /* Select the Master Slave Mode */
    TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);
    /* Master Mode selection */
    TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);
    
// 配置TIM3为从定时器
    /* Slave Mode selection: TIM3 */
    TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Gated);
    TIM_SelectInputTrigger(TIM3, TIM_TS_ITR1);
    
    TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);
   
    TIM_Cmd(TIM2, DISABLE);
    TIM_Cmd(TIM3, DISABLE);
}

中断服务程序如下：


u8  TIM2_Pulse_TIM3_Counter_OK = 0;
void TIM3_IRQHandler(void)
{
    if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)
    {
        TIM_ClearITPendingBit(TIM3, TIM_IT_CC1);    // 清除中断标志位
        
        TIM_Cmd(TIM2, DISABLE); // 关闭定时器
        TIM_Cmd(TIM3, DISABLE); // 关闭定时器
        
        TIM2_Pulse_TIM3_Counter_OK = 1;
    }
}

应用程序为：

u16 pulsecnt = 10000;
void main(void)
{
    SystemSetup();        // 初始化内核和外设
    TIM2_Master__TIM3_Slave_Configuration(10000);//配置TIM2的脉冲输出为10k
    while(1)
    {
        TIM_ITConfig(TIM3, TIM_IT_CC1, DISABLE);        /* TIM enable counter */
        TIM_Cmd(TIM3, ENABLE);
        TIM3->CCR1  = pulsecnt;
        TIM3->CNT   = 0;
        TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);
        TIM_Cmd(TIM2, ENABLE);    /* TIM enable counter */
        
        while(TIM2_Pulse_TIM3_Counter_OK  == 0);
    }
}

这种配置方式下，使用的是TIM3的比较中断，我还没试验过其他的方式，想来应该也是可以的，比如用定时器更新中断……