为了控制采样时间，可以使用一个定时器的TRGO（定时器里每次发生更新事件时会有这个信号产生）作为定时器的外部触发。
从定时器框图可以看出,TRGO为TIMx的一个输出.不过这个输出是内部使用的。
void myADC_Init()
{
ADC_InitTypeDef ADC_InitStruct;
GPIO_InitTypeDef GPIO_InitStruct;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 ,ENABLE);
RCC_ADCCLKConfig(RCC_PCLK2_Div6);
//ADC1_Init
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_1 | GPIO_Pin_0;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AIN;
GPIO_Init(GPIOA,&GPIO_InitStruct);
ADC_DeInit(ADC1);
ADC_InitStruct.ADC_Mode = ADC_Mode_Independent;
ADC_InitStruct.ADC_NbrOfChannel = 1;
ADC_InitStruct.ADC_ContinuousConvMode = DISABLE;
ADC_InitStruct.ADC_ScanConvMode = DISABLE;
ADC_InitStruct.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
ADC_InitStruct.ADC_DataAlign =ADC_DataAlign_Right;
ADC_Init(ADC1,&ADC_InitStruct);
ADC_ExternalTrigConvCmd(ADC1,ENABLE);
//ENABLE ADC1
ADC_RegularChannelConfig(ADC1,0,1,ADC_SampleTime_1Cycles5);
ADC_DMACmd(ADC1,ENABLE);
ADC_Cmd(ADC1,ENABLE);
ADC_ResetCalibration(ADC1);
while(ADC_GetResetCalibrationStatus(ADC1));
ADC_StartCalibration(ADC1);
while(ADC_GetCalibrationStatus(ADC1));
}
void TIM3_Init()
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
NVIC_InitTypeDef NVIC_InitStruct;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInitStruct.TIM_Period = 72000000/SampleRate;
TIM_TimeBaseInitStruct.TIM_Prescaler = 0;
TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStruct);
TIM_SelectOutputTrigger(TIM3,TIM_TRGOSource_Update); //选择TRGO触发源为计时器更新时间
TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE);
NVIC_InitStruct.NVIC_IRQChannel = TIM3_IRQn;
NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStruct.NVIC_IRQChannelSubPriority = 3;
NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStruct);
TIM_Cmd(TIM3,ENABLE);
}