F3 差分ADC 输入短路，输出居然是0x07FF?

uzufk 提问时间：2013-3-21 10:02 /

STM32F3探索套件 差分ADC 输入短路，输出居然是0x07FF?
找了好几天原因没找到，那位了解，告诉一声！
单端方式试过，没有问题。
以下是我测试的程序：
ADC配置部分
ADC_InitTypeDef       ADC_InitStructure;
ADC_CommonInitTypeDef ADC_CommonInitStructure;
GPIO_InitTypeDef    GPIO_InitStructure;

   /* Configure the ADC clock */
RCC_ADCCLKConfig(RCC_ADC12PLLCLK_Div2);

/* Enable ADC1 clock */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_ADC12, ENABLE);

   /* ADC Channel configuration */
   /* GPIOC Periph clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
/* Configure ADC Channel7 as analog input */
// GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1 | GPIO_Pin_2;
// GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
// GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
// GPIO_Init(GPIOC, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
GPIO_Init(GPIOA, &GPIO_InitStructure);

ADC_StructInit(&ADC_InitStructure);
/* Calibration procedure */
ADC_VoltageRegulatorCmd(ADC1, ENABLE);

/* Insert delay equal to 10 ¦Ìs */
Delay(10);


ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_CommonInitStructure.ADC_Clock = ADC_Clock_AsynClkMode;
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
ADC_CommonInitStructure.ADC_DMAMode = ADC_DMAMode_OneShot;
ADC_CommonInitStructure.ADC_TwoSamplingDelay = 0;

ADC_CommonInit(ADC1, &ADC_CommonInitStructure);

ADC_InitStructure.ADC_ContinuousConvMode = ADC_ContinuousConvMode_Enable;
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ExternalTrigConvEvent = ADC_ExternalTrigConvEvent_0;
ADC_InitStructure.ADC_ExternalTrigEventEdge = ADC_ExternalTrigEventEdge_None;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_OverrunMode = ADC_OverrunMode_Disable;
ADC_InitStructure.ADC_AutoInjMode = ADC_AutoInjec_Disable;
ADC_InitStructure.ADC_NbrOfRegChannel = 1;
ADC_Init(ADC1, &ADC_InitStructure);

/* ADC1 regular channel7 and channel8 configuration */
//   ADC_RegularChannelConfig(ADC1, ADC_Channel_7, 1, ADC_SampleTime_7Cycles5);
//   ADC_RegularChannelConfig(ADC1, ADC_Channel_8, 2, ADC_SampleTime_7Cycles5);
ADC_RegularChannelConfig(ADC1, ADC_Channel_1, 1, ADC_SampleTime_7Cycles5);
//   ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 2, ADC_SampleTime_7Cycles5);

/* Select the differetiel mode for Channel 7 */
ADC_SelectDifferentialMode(ADC1, ADC_Channel_1, ENABLE);

ADC_SetChannelOffset1(ADC1,ADC_Channel_1,0);
ADC_SetChannelOffset1(ADC1,ADC_Channel_2,0);
ADC_ChannelOffset1Cmd(ADC1,ENABLE);

ADC_SelectCalibrationMode(ADC1, ADC_CalibrationMode_Differential);
ADC_StartCalibration(ADC1);

while(ADC_GetCalibrationStatus(ADC1) != RESET );
calibration_value = ADC_GetCalibrationValue(ADC1);

/* Enable ADC1 */
ADC_Cmd(ADC1, ENABLE);

/* wait for ADRDY */
while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_RDY));

/* Start ADC1 Software Conversion */
ADC_StartConversion(ADC1);
//