频率 10K，占空比可以达到1%变化的精度，100K只能是10%的变化精度。

#define PWM_CLK1M_ARR_10K 100-1

void IzADCPWMInit(uint8_t duty)//10%~90%

{

  if(duty>90)

  {

 duty = 90;

  }

  if(duty<10)

  {

 duty = 10;

  } 

//reset 

  /* TIM4 enable counter */

  TIM_Cmd(TIM4, DISABLE);

   /* TIM4 Main Output Enable */

  TIM_CtrlPWMOutputs(TIM4, DISABLE); 

//end of reset

    /* System Clocks Configuration */

  RCCPWMADCConfiguration();

  /* GPIO Configuration */

  GPIOPWMADCConfiguration();

  /* -----------------------------------------------------------------------

    TIM3 Configuration: generate 4 PWM signals with 4 different duty cycles:

    The TIM3CLK frequency is set to SystemCoreClock (Hz), to get TIM3 counter

    clock at 24 MHz the Prescaler is computed as following:

     - Prescaler = (TIM3CLK / TIM3 counter clock) - 1

    SystemCoreClock is set to 72 MHz for Low-density, Medium-density, High-density

    and Connectivity line devices and to 24 MHz for Low-Density Value line and

    Medium-Density Value line devices

    The TIM3 is running at 36 KHz: TIM3 Frequency = TIM3 counter clock/(ARR + 1)

                                                  = 24 MHz / 666 = 36 KHz

    TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR)* 100 = 50%

    TIM3 Channel2 duty cycle = (TIM3_CCR2/ TIM3_ARR)* 100 = 37.5%

    TIM3 Channel3 duty cycle = (TIM3_CCR3/ TIM3_ARR)* 100 = 25%

    TIM3 Channel4 duty cycle = (TIM3_CCR4/ TIM3_ARR)* 100 = 12.5%

  ----------------------------------------------------------------------- */

  /* Compute the prescaler value */

  //PrescalerValue = (uint16_t) (SystemCoreClock / 24000000) - 1;//24M

  //TIM3 Frequency=1MHz/(9999+1) =100Hz

  PrescalerValue = (uint16_t) (SystemCoreClock / 1000000) - 1; //TIM3 counter clock: 1MHz

  /* Time base configuration */

  //TIM_TimeBaseStructure.TIM_Period = 665;//(ARR)

  //TIM3 Frequency=1MHz/(9999+1) =100Hz

  //TIM_TimeBaseStructure.TIM_Period = 10000-1;  //TIM3 counter clock/TIM3 Frequency

  //TIM3 Frequency=1MHz/(99+1) =10 000Hz

  TIM_TimeBaseStructure.TIM_Period = PWM_CLK1M_ARR_10K;//PWM_CLK1M_ARR_100;  //TIM3 counter clock/TIM3 Frequency 

  TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;

  TIM_TimeBaseStructure.TIM_ClockDivision = 0;

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

  /* PWM1 Mode configuration: Channel1 */

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  //CCR1_Val =TIM3_ARR*duty/100;

 // TIM_OCInitStructure.TIM_Pulse = CCR1_Val;

 // TIM_OCInitStructure.TIM_Pulse = (uint16_t)(10000-1)*duty/100; 

  TIM_OCInitStructure.TIM_Pulse = (uint16_t)(PWM_CLK1M_ARR_10K)*duty/100;   

  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

//  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

//  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

//PB6: TM4 Channel1  

  TIM_OC1Init(TIM4, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable); 

//PB8: TM4 Channel3

  /* PWM1 Mode configuration: Channel3 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = (uint16_t)(PWM_CLK1M_ARR_10K)*duty/100;   

  TIM_OC3Init(TIM4, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);

//PB7: TM4 Channel2

  /* PWM1 Mode configuration: Channel2 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse =  (uint16_t)(PWM_CLK1M_ARR_10K)*duty/100; ;

  TIM_OC2Init(TIM4, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM4, TIM_OCPreload_Enable);

#if 0

  /* PWM1 Mode configuration: Channel4 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = CCR4_Val;

  TIM_OC4Init(TIM3, &TIM_OCInitStructure);

  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

#endif

  TIM_ARRPreloadConfig(TIM4, ENABLE);

  /* TIM4 enable counter */

  TIM_Cmd(TIM4, ENABLE);

   /* TIM4 Main Output Enable */

  TIM_CtrlPWMOutputs(TIM4, ENABLE);

}