TIMER门控模式控制PWM输出长度

//TIM2 PWM输出，由TIM4来控制其输出与停止
//frequency_tim2：TIM2 PWM输出周期：KHz
//duty_tim2：TIM2 PWM占空比  0-100
//period_tim4: TIM4控制TIM2总周期，单位0.1ms
//duty_tim4: TIM4控制TIM2输出时间，单位0.1ms

void TIM2_CH3_PA2_PWM_TIM4_CH4_GATE( unsigned short int frequency_tim2,
  char duty_tim2, unsigned short int period_tim4, unsigned short int duty_tim4 )
{
  
  GPIO_InitTypeDef GPIO_InitStructure;
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
  TIM_OCInitTypeDef TIM_OCInitStructure;
  
  RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM2 | RCC_APB1Periph_TIM4, ENABLE ); 
  //使能定时器2时钟
  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE ); 
  //使能GPIO外设和AFIO复用功能模块时钟
    
  //设置该引脚为复用输出功能,输出TIM2 CH3的PWM脉冲波形 GPIOA.2
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; //TIM2_CH3
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用推挽输出
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init( GPIOA, &GPIO_InitStructure );  //初始化GPIO
    
  //初始化TIM2
  TIM_TimeBaseStructure.TIM_Period = ( 1000 / frequency_tim2 ); 
  //设置在下一个更新事件装入活动的自动重装载寄存器周期的值,本身频率为1MHz，又分频器设置的下面一行
  TIM_TimeBaseStructure.TIM_Prescaler = ( 72 - 1 ); 
  //设置用来作为TIMx时钟频率除数的预分频值，72MHz/72=1MHz 
  TIM_TimeBaseStructure.TIM_ClockDivision = 0; 
  //设置时钟分割:TDTS = Tck_tim
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
  //TIM向上计数模式
  TIM_TimeBaseInit( TIM2, &TIM_TimeBaseStructure ); 
  //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位
    
  //初始化TIM2 Channel3 PWM模式  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 
  //选择定时器模式:TIM脉冲宽度调制模式2
  TIM_OCInitStructure.TIM_Pulse = ( 10 * duty_tim2 / frequency_tim2 ); 
  //(TIM_Period)*(duty/100) --> (1000/period)*(duty/100)
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 
  //比较输出使能
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 
  //输出极性:TIM输出比较极性高
  TIM_OC3Init( TIM2, &TIM_OCInitStructure );  
  //根据T指定的参数初始化外设TIM2 OC3
    
  TIM_OC3PreloadConfig( TIM2, TIM_OCPreload_Enable );  
  //使能TIM2在CCR3上的预装载寄存器 
  TIM_Cmd( TIM2, ENABLE );  //使能TIM2
    
  //初始化TIM4
  TIM_TimeBaseStructure.TIM_Period = period_tim4; 
  //设置在下一个更新事件装入活动的自动重装载寄存器周期的值,本身频率为1MHz，又分频器设置的下面一行
  TIM_TimeBaseStructure.TIM_Prescaler = ( 7200 - 1 ); 
  //设置用来作为TIMx时钟频率除数的预分频值，72MHz/72=1MHz 
  TIM_TimeBaseStructure.TIM_ClockDivision = 0; 
  //设置时钟分割:TDTS = Tck_tim
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
  //TIM向上计数模式
  TIM_TimeBaseInit( TIM4, &TIM_TimeBaseStructure ); 
  //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位
    
  //初始化TIM4 Channel4 PWM模式  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 
  //选择定时器模式:TIM脉冲宽度调制模式2
  TIM_OCInitStructure.TIM_Pulse = duty_tim4; 
  //(TIM_Period)*(duty/100) --> (1000/period)*(duty/100)
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 
  //比较输出使能
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; 
  //输出极性:TIM输出比较极性高
  TIM_OC4Init( TIM4, &TIM_OCInitStructure );  
  //根据T指定的参数初始化外设TIM4 OC4
    
  TIM_OC4PreloadConfig( TIM4, TIM_OCPreload_Enable );  
  //使能TIM4在CCR4上的预装载寄存器 
  TIM_Cmd( TIM4, ENABLE );  //使能TIM4
    
  TIM_SelectInputTrigger( TIM2, TIM_TS_ITR3 ); 
  //选择有效输入端 ,查表得知TIM4对于TIM2是ITR3       
  TIM_SelectSlaveMode( TIM2, TIM_SlaveMode_Gated );  
  //配置为主从复位模式
  TIM_SelectOutputTrigger( TIM4, TIM_TRGOSource_OC4Ref );
  /* Enable timer‘s master/slave work mode */
  TIM_SelectMasterSlaveMode( TIM2, TIM_MasterSlaveMode_Enable );   //Slave
  TIM_SelectMasterSlaveMode( TIM4, TIM_MasterSlaveMode_Enable );   //Master
    
}