STM32F1用单次AD采样和AD+DMA连续采样的结果有偏差是怎么回事？

请教大家一个问题， 硬件是一样的，采样电阻接地。
负载不工作：AD单次采样时，可以采样到0x 00;AD+DMA连续采样，采样到 0x 0F到0x 12抬高了采样值，负载开启时：AD单次采样时，可以采样到0x 67 左右波动;AD+DMA连续采样，采样到 0x89  左右波动;
抬高了采样值，是我那里没有设置好吗，我就在例程上修改一个脚，从PC1改到PA1.
include "adc.h"

define ADC1_DR_Address    ((u32)0x40012400+0x4c)

__IO uint16_t ADC_ConvertedValue;
static void ADC1_GPIO_Config(void){GPIO_InitTypeDef GPIO_InitStructure;
/ Enable DMA clock /RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
/ Enable ADC1 and GPIOC clock /RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 | RCC_APB2Periph_GPIOA, ENABLE);
/ Configure PC.01  as analog input /GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;GPIO_Init(GPIOA,  GPIO_InitStructure);                                // }
static void ADC1_Mode_Config(void){DMA_InitTypeDef DMA_InitStructure;ADC_InitTypeDef ADC_InitStructure;
/ DMA channel1 configuration /DMA_DeInit(DMA1_Channel1);DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;         //DMA_InitStructure.DMA_MemoryBaseAddr = (u32) ADC_ConvertedValue;//DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;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_M2M = DMA_M2M_Disable;DMA_Init(DMA1_Channel1,  DMA_InitStructure);
/ Enable DMA channel1 /DMA_Cmd(DMA1_Channel1, ENABLE);
/ ADC1 configuration /
ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;        //ADC_InitStructure.ADC_ScanConvMode = DISABLE ;          //ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;        //ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;        //ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;         //ADC_InitStructure.ADC_NbrOfChannel = 1;                 //ADC_Init(ADC1,  ADC_InitStructure);
RCC_ADCCLKConfig(RCC_PCLK2_Div8);
ADC_RegularChannelConfig(ADC1, ADC_Channel_1, 1, ADC_SampleTime_55Cycles5);
/ Enable ADC1 DMA /ADC_DMACmd(ADC1, ENABLE);
/ Enable ADC1 /ADC_Cmd(ADC1, ENABLE);
ADC_ResetCalibration(ADC1);
while(ADC_GetResetCalibrationStatus(ADC1));
ADC_StartCalibration(ADC1);
while(ADC_GetCalibrationStatus(ADC1));
ADC_SoftwareStartConvCmd(ADC1, ENABLE);}
void ADC1_Init(void)
{ADC1_GPIO_Config();
ADC1_Mode_Config();}