本帖最后由 hpdell 于 2015-7-18 13:46 编辑
外部电池直接加到单片机的vbat引脚
请教下，stm32f4xx  vbat 转换出来的电压不准，是什么情况 ？

#define ADCx                     ADC1
  #define ADCx_CLK                 RCC_APB2Periph_ADC1
  #define DMA_CHANNELx             DMA_Channel_0
  #define DMA_STREAMx              DMA2_Stream4
  #define ADCx_DR_ADDRESS          ((uint32_t)0x4001204C)

uint16_t ADCConvVbatValue = 0;

void ADC_VbatInit_Configuration(void)
{
//        ADC_VbatDMA_Config();
//        ADC1_ChVbat_DMA_Config();
        
        
  ADC_InitTypeDef       ADC_InitStructure;
  ADC_CommonInitTypeDef ADC_CommonInitStructure;
  DMA_InitTypeDef       DMA_InitStructure;
    
  /* Enable peripheral clocks *************************************************/
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
  RCC_APB2PeriphClockCmd(ADCx_CLK, ENABLE);

  /* DMA2_Stream0 channel0 configuration **************************************/
  DMA_DeInit(DMA_STREAMx);
  DMA_InitStructure.DMA_Channel = DMA_CHANNELx;  
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADCx_DR_ADDRESS;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADCConvVbatValue;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
  DMA_InitStructure.DMA_BufferSize = 1;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;         
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA_STREAMx, &DMA_InitStructure);
  /* DMA2_Stream0 enable */
  DMA_Cmd(DMA_STREAMx, ENABLE);
    
  /* ADC Common Init **********************************************************/
  ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
  ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
  ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
  ADC_CommonInit(&ADC_CommonInitStructure);

  /* ADC1 Init ****************************************************************/
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfConversion = 1;
  ADC_Init(ADCx, &ADC_InitStructure);

  /* Enable ADC1 DMA */
  ADC_DMACmd(ADCx, ENABLE);
  
  /* ADC1 regular channel18 (VBAT) configuration ******************************/
  ADC_RegularChannelConfig(ADCx, ADC_Channel_Vbat, 1, ADC_SampleTime_15Cycles);

  /* Enable VBAT channel */
  ADC_VBATCmd(ENABLE); 

  /* Enable DMA request after last transfer (Single-ADC mode) */
  ADC_DMARequestAfterLastTransferCmd(ADCx, ENABLE);

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

        /* Start ADC1 Software Conversion */
        ADC_SoftwareStartConv(ADC1);
        
        Delay_Ms(200);
                
}


void VBAT_DispValue(void)
{
        float dat;
        char  datdat[19];
        
        dat = (float)((ADCConvVbatValue * 2) * ADC_BASS_VOLATE / 4095);                        //计算出备份电池的电压 这里*2还是不行，需要*4貌似才正确， 何故 ？？？
        

        //                                GUI_SetColor(GUI_RED);   // 设置显示颜 {MOD}
        sprintf((char *)&datdat[0], "VBAT Voltage:%1.2fV", (float)dat);
        GUI_GotoXY               (10, 340);
        GUI_DispString(( char *)&datdat[0]);        
        
}