ADS1220采集不了0.6mv以下的电压
采用stm32驱动ads1220，ads1220连接图如图1所示，两个单端输入信号，ref+（3.298V）作为外部参考电压，但是使用采用了内部2.048V的参考电压，程序初始化时设置如下：
ADS1220_Reset(); //复位
void Setup_ADS1220 (unsigned char inputMux, unsigned char gainLevel) //初始化设置
{
unsigned char config[4];
config[0] = inputMux + gainLevel + ADS1220_PGA_BYPASS;
config[1] = ADS1220_DATA_RATE_175SPS+ ADS1220_OP_MODE_NORMAL + ADS1220_CONVERSION_SINGLE_SHOT + ADS1220_TEMP_SENSOR_OFF + ADS1220_BURN_OUT_CURRENT_OFF;
config[2] = ADS1220_FIR_50_60 + ADS1220_VREF_INTERNAL + ADS1220_LOW_SIDE_POWER_CLOSES + ADS1220_IDAC_CURRENT_OFF;
config[3] = ADS1220_IDAC1_DISABLED + ADS1220_IDAC2_DISABLED + ADS1220_DRDY_ON_DRDY_ONLY;
switch (gainLevel)
{
case ADS1220_GAIN_1:
PgaGainLevel = 1.0;
break;
case ADS1220_GAIN_2:
PgaGainLevel = 2.0;
break;
case ADS1220_GAIN_4:
PgaGainLevel = 4.0;
break;
case ADS1220_GAIN_8:
PgaGainLevel = 8.0;
break;
case ADS1220_GAIN_16:
PgaGainLevel = 16.0;
break;
case ADS1220_GAIN_32:
PgaGainLevel = 32.0;
break;
case ADS1220_GAIN_64:
PgaGainLevel = 64.0;
break;
case ADS1220_GAIN_128:
PgaGainLevel = 128.0;
break;
}
ADS1220_Write_Regs (config, ADS1220_CONFIG_0_REG, 4);
delay_us(10);
ADS1220_Read_Regs (config, ADS1220_CONFIG_0_REG, 4);
}
main函数中while（1）循环如下：
Change_ADS1220(ADS1220_MUX_AIN0_AIN1,ADS1220_GAIN_32); //设置输入端口和放大倍数
delay_ms(1);
for(i=0;i<12;i++) //采集12次，去除最大最小求均值
{
ADS1220_Start();
delay_us(1);
while(ADC_RDY_DAT);
delay_us(2);
ADS1220_Get_Conversion_Data((unsigned char *)tempData);
Databuffer[i] = ADS1220_Gain_vlotage(tempData);
这个是电压转换函数：
double ADS1220_Gain_vlotage (unsigned char *tempData)
{
volatile long temp = 0;
volatile double voltage = 0;
temp = tempData[0];
temp <<= 8;
temp |= tempData[1];
temp <<= 8;
temp |= tempData[2];
// Was temp negative?
if (tempData[0] & 0x80)
{
temp |= 0xff000000;
}
voltage =(double)temp*VREF/0x7fffff/PgaGainLevel;
return voltage;
}
其中：
void Change_ADS1220 (unsigned char inputMux, unsigned char gainLevel)
{
unsigned char config;
config = inputMux + gainLevel + ADS1220_USE_PGA ;
switch (gainLevel)
{
case ADS1220_GAIN_1:
PgaGainLevel = 1.0;
break;
case ADS1220_GAIN_2:
PgaGainLevel = 2.0;
break;
case ADS1220_GAIN_4:
PgaGainLevel = 4.0;
break;
case ADS1220_GAIN_8:
PgaGainLevel = 8.0;
break;
case ADS1220_GAIN_16:
PgaGainLevel = 16.0;
break;
case ADS1220_GAIN_32:
PgaGainLevel = 32.0;
break;
case ADS1220_GAIN_64:
PgaGainLevel = 64.0;
break;
case ADS1220_GAIN_128:
PgaGainLevel = 128.0;
break;
}
ADS1220_Write_Regs (&config, ADS1220_CONFIG_0_REG, 1);
delay_us(10);
ADS1220_Read_Regs (&config, ADS1220_CONFIG_0_REG, 1);
}
即主循环使用的是ADS1220_MUX_AIN0_AIN1端口采集输入，32倍的增益，按照2.048/2^24=0.001mV 为最低可检测到的电压，为什么输入0.3mV采集到的数据为0.001mV呢（采不准，并且更换了更大的放大倍数也一样），也就是基本采集不到？同时100mV以上采集到的电压也相差0.5mV，这是ads1220硬件连接问题还是软件问题？
是不是电路噪声太大了？或者你的输入本身就比较大的噪声？
你直接把输入接地，看看采样出来的值跳变有多大。
把输入接地时采集到的电压为0.003~0.005跳变，该怎么解决0.6mV以下测不到，及100mv以下测不准的问题呢？
这个芯片多少位分辨率？你的信号频率多少？
小电压信号传输过程有衰减。
另外需要考虑电源纹波影响！
把输入端接地采集到的电压是0.054mV，这个得怎么处理呢？是在程序中直接把采集到的电压减去0.054mv？还是硬件上怎么处理？
可能是布板或者电源噪声有影响。
你尝试做下多次平均，看能不能消除
单端输入方式吗？
对照数据手册检查是否满足共模电压范围要求。