LTC1867芯片单极模式只能采样0~2V

木子电子 · 发表于 2018-1-30 09:48:03

在stm32f107基础上使用LTC1867芯片采样，设置单极性后只能采样要0~2V的电压，基准为4V。请大神帮忙！！！！
0~2V采样正常，2~4V读到的电压又从0开始递增。实际电压0V对应采集值0V,实际电压2V对应采集值为2V，2.01V开始就变成了0V，实际电压4V对应的采集值是1.996V。确认配置为单极性。[mw_shl_code=applescript,true]#define    ADC_CS_H                   GPIO_SetBits(GPIOA,GPIO_Pin_4);
#define    ADC_CS_L                   GPIO_ResetBits(GPIOA,GPIO_Pin_4);

#define    ADC_SCK_H                GPIO_SetBits(GPIOA,GPIO_Pin_5);
#define    ADC_SCK_L                GPIO_ResetBits(GPIOA,GPIO_Pin_5);

//#define ADC_MISO             GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_6)
#define    ADC_MISO             GPIOA->IDR&(1<<6)

#define    ADC_MOSI_H             GPIO_SetBits(GPIOA,GPIO_Pin_7);
#define    ADC_MOSI_L             GPIO_ResetBits(GPIOA,GPIO_Pin_7);

#define    Instructions_LTC1867_CH0                      0x80
#define    Instructions_LTC1867_CH1                   0xC0
#define    Instructions_LTC1867_CH2                      0x90
#define Instructions_LTC1867_CH3                   0xD0
#define    Instructions_LTC1867_CH4                      0xA0
#define    Instructions_LTC1867_CH5                   0xE0
#define    Instructions_LTC1867_CH6                      0xB0
#define Instructions_LTC1867_CH7                   0xF0

#define    LTC1867_SLEEP_MODE                               0x02
#define    LTC1867_EXIT_SLEEP_MODE                      0x00
#define    LTC1867_UNIPOLAR_MODE                         0x04
#define    LTC1867_BIPOLAR_MODE                               0x00

/******************************************

*功能：SPI初始化

*******************************************/
void SPI_GPIO_Init(void)
{
      GPIO_InitTypeDef GPIO_InitStructure;

      RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);

      //----------------------GPIO----------------------
      // Configure SPI pins: CS
      GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_Init(GPIOA, &GPIO_InitStructure);


      // Configure SPI pins: SCK
      GPIO_InitStructure.GPIO_Pin = 0;
      GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
      GPIO_Init(GPIOA, &GPIO_InitStructure);

      // Configure SPI pins: MISO
      GPIO_InitStructure.GPIO_Pin = 0;
      GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
      GPIO_Init(GPIOA, &GPIO_InitStructure);

      // Configure _SPI pins: MOSI
      GPIO_InitStructure.GPIO_Pin = 0;
      GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
      GPIO_Init(GPIOA, &GPIO_InitStructure);

      //设置为空闲状态
   ADC_CS_H;
   ADC_SCK_H;

}

/************************************************

*功能： LTC1867ACGN选择1~8通道

*************************************************/
u8 LTC1867ACGN_SetChnl(u8 chnl)
{
      u8 cmd;
      switch(chnl)
      {
            case 1:
                  cmd = Instructions_LTC1867_CH0|LTC1867_UNIPOLAR_MODE;break;

            case 2:
                  cmd = Instructions_LTC1867_CH1|LTC1867_UNIPOLAR_MODE;break;

            case 3:
                  cmd = Instructions_LTC1867_CH2|LTC1867_UNIPOLAR_MODE;break;

            case 4:
                  cmd = Instructions_LTC1867_CH3|LTC1867_UNIPOLAR_MODE;break;

            case 5:
                  cmd = Instructions_LTC1867_CH4|LTC1867_UNIPOLAR_MODE;break;

            case 6:
                  cmd = Instructions_LTC1867_CH5|LTC1867_UNIPOLAR_MODE;break;

            case 7:
                  cmd = Instructions_LTC1867_CH6|LTC1867_UNIPOLAR_MODE;break;

            case 8:
                  cmd = Instructions_LTC1867_CH7|LTC1867_UNIPOLAR_MODE;break;

            default:
                  cmd = Instructions_LTC1867_CH0|LTC1867_UNIPOLAR_MODE;break;
      }
      return cmd;
}

/**********************************

*功能： SPI读写数据，给定通道选择参数

***********************************/
u16 SPI_WriteRead(u8 chnl)
{
      u8 i = 0;
      u16 dat = 0;
      u8 cmd = 0;
      cmd = LTC1867ACGN_SetChnl(chnl);
      ADC_CS_L;
      delay_5us(10);                //50
      for(i=0;i<7;i++)
      {
            if(cmd&(0x80))
            {
                     ADC_MOSI_H;
            }else{
                     ADC_MOSI_L;
            }
            cmd <<= 1;
            ADC_SCK_L;
            delay_5us(1);          //5
            ADC_SCK_H;
            delay_5us(1);          //5
      }
      ADC_CS_H;
      delay_5us(2);                //10
      ADC_CS_L;
      for(i=0;i<16;i++)
      {
            ADC_SCK_L;
            delay_5us(1);          //2
            if(ADC_MISO) dat |= 1;
            dat <<= 1;
            ADC_SCK_H;
            delay_5us(1);          //2
      }
      ADC_CS_H;

      return dat;
}[/mw_shl_code]