下面这段是ADC的初始化，请问这采样频率是怎么算的？
  ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div4;// ADC_Prescaler_Div2
    ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
    ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
    ADC_CommonInit(&ADC_CommonInitStructure);

    /* ADC1 ****************************************************************/
    ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
    ADC_InitStructure.ADC_ScanConvMode = ENABLE;//ɨÃèģʽ        
    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;//Á¬Ðøת»»
    ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;        
    ADC_InitStructure.ADC_NbrOfConversion = 1;
    ADC_Init(ADC1, &ADC_InitStructure);
   ADC_RegularChannelConfig(ADC1, ADC_Channel_12, 1, ADC_SampleTime_480Cycles);
如果需要上定时器的部分，麻烦各位老哥帮个忙吧= =网上找不找具体的计算方式。
       TIM_TimeBaseStructure.TIM_Period = 1;         
        TIM_TimeBaseStructure.TIM_Prescaler = 1000;
        TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;   
        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
        TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);