最近在做电流型信号输出的项目，遇到了些问题这里把这些解决方法做一个笔记方便以后运用。在搞这个的时候因为手册这部分讲的不是很详细，所以在使用上也遇到了些阻力。

用的是64封装的芯，此芯ADC的基准Vref+和电源是同一个端口，Vref-共用电源地。在电池输出时AD值为0时 取样电阻100欧姆 有0.66mA的电流输出，只要在初始化时只要失能端口输出缓冲，输出可到0.0025mA。OK问题就解决了。

 1 void AnalogInit(void)

 2 {

 3     DAC_InitTypeDef  DAC_InitStructure;

 4     GPIO_InitTypeDef GPIO_InitStructure;

 5 

 6       RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO | RCC_APB2Periph_GPIOA, ENABLE);

 7       /* DAC Periph clock enable */

 8       RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);

 9       

10     /* Configure DAC channe1 output pin */

11     GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_4;

12     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

13     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;

14     GPIO_Init(GPIOA, &GPIO_InitStructure);

15 

16     /* Configure DAC channe1 output pin */

17     GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_5;

18     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

19     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;

20     GPIO_Init(GPIOA, &GPIO_InitStructure);

21 

22     

23     /* DAC channel1 Configuration */

24     DAC_InitStructure.DAC_Trigger = DAC_Trigger_Software;

25     DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;

26     DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;    //输出缓冲失能    

27     DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_4095;

28 

29     DAC_Init(DAC_Channel_1, &DAC_InitStructure);

30 

31     /* DAC channel2 Configuration */

32     DAC_Init(DAC_Channel_2, &DAC_InitStructure);

33 

34     /* Enable DAC Channel1: Once the DAC channel1 is enabled, PA.04 is 

35     automatically connected to the DAC converter. */

36     DAC_Cmd(DAC_Channel_1, ENABLE);

37     /* Enable DAC Channel2: Once the DAC channel2 is enabled, PA.05 is 

38     automatically connected to the DAC converter. */

39     DAC_Cmd(DAC_Channel_2, ENABLE);

40 

41 }

42 

43 //端口1AD值更新

44 void DAC1_update(u16 ch1)

45 {

46     ch1 = (ch1 <<4) & 0xfff0;

47     /* Set DAC Channel1 DHR12L register */

48     DAC_SetChannel1Data(DAC_Align_12b_L, ch1);

49 

50     /* Start DAC Channel1 conversion by software */

51     DAC_SoftwareTriggerCmd(DAC_Channel_1, ENABLE);

52 }

53 

54 void DAC2_update(u16 ch2)

55 {

56     ch2 = (ch2 <<4) & 0xfff0;

57     /* Set DAC Channel2 DHR12L register */

58     DAC_SetChannel2Data(DAC_Align_12b_L, ch2);

59 

60     /* Start DAC Channel1 conversion by software */

61     DAC_SoftwareTriggerCmd(DAC_Channel_2, ENABLE);

62 }