STM32F103ZET6 用定時器級聯方式輸出特定數目的PWM

STM32F103ZET6 用定時器級聯方式輸出特定數目的PWM

STM32F103ZET6里共有8個定時器，其中高級定時器有TIM1-TIM5、TIM8，共6個。

這里需要使用定時器的級聯功能，ST的RM0008 REV12的P388和P399頁上有說明對於特定的定時器，怎么去選擇級聯功能，參見表86。

我這里輸出PWM的定時器是TIM2，空閑的定時器是TIM3。以TIM2為主定時器，TIM3為從定時器對TIM2的輸出脈沖數進行計數。

查表可知，TIM3為從定時器選擇TIM2為觸發源，需要配置TS=001，即選擇ITR1。

實現通過定時器控制輸出PWM個數的功能，可以有如下一種配置方式：

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;    

// 時基配置：配置PWM輸出定時器——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);

    
// 輸出配置：配置PWM輸出定時器——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);
    
// 時基配置：配置脈沖計數寄存器——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; // 這里的配置值意義不大
    
    TIM_OC1Init(TIM3, &TIM_OCInitStructure);
    
// 配置TIM2為主定時器
    /* Select the Master Slave Mode */
    TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);
    /* Master Mode selection */
    TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);
    
// 配置TIM3為從定時器
    /* 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);
}

中斷服務程序如下：


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);    // 清除中斷標志位
        
        TIM_Cmd(TIM2, DISABLE); // 關閉定時器
        TIM_Cmd(TIM3, DISABLE); // 關閉定時器
        
        TIM2_Pulse_TIM3_Counter_OK = 1;
    }
}

應用程序為：

u16 pulsecnt = 10000;
void main(void)
{
    SystemSetup();        // 初始化內核和外設
    TIM2_Master__TIM3_Slave_Configuration(10000);//配置TIM2的脈沖輸出為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);
    }
}

這種配置方式下，使用的是TIM3的比較中斷，我還沒試驗過其他的方式，想來應該也是可以的，比如用定時器更新中斷……