[资料分享] ADS1263测量三线制PT100（RTD）电阻的配置代码

littleshrimp 2017-8-25 11:28 楼主

使用ADS1263内部恒流源，IDAC1=IDAC2=1.5mA 参考电阻使用820ohm 参考下边贴子可以将对应电阻转换为温度 https://bbs.eeworld.com.cn/thread-553748-1-1.html

代码中的公式 resistance = ((double) AdcOutput / gain) / 2147483640.00f * 2.00f * 820.00f; AdcOutput 是读取到的ADC码，gain是PGA的增益，AdcOutput / gain得到实际RTD两端的电压 2147483640.00f是2^31，32位ADC输出范围是±2147483640 * 2.00f 是因为RTD流过的电流是1.5mA,参考电阻流过的电路是1.5*2=3mA * 820.00f得到RTD的实际阻值

double get_resistance(uint8 gain)
{
uint8 WriteRegData; //Stores the register write values
uint8 AdcRegData[ADS126x_NUM_REG]; //Stores the register read values
int32 AdcOutput = 0;
uint8 gainBit = 0;
double resistance;
//Read ALL registers
ADS126xReadRegister(ID, ADS126x_NUM_REG, AdcRegData);
//MODE0 (CHOP OFF)
WriteRegData = (AdcRegData[MODE0] & DELAY_MASK);
ADS126xWriteRegister(MODE0, 1, &WriteRegData);
//POWER VBIAS OFF
WriteRegData = (AdcRegData[POWER] & ~VBIAS);
ADS126xWriteRegister(MODE0, 1, &WriteRegData);
//(IDACMUX) IDAC2 AIN0,IDAC1 AIN3
WriteRegData = (AdcRegData[(IDACMUX)] & ~(MUX2_MASK | MUX1_MASK)) | MUX2_AIN0 | MUX1_AIN3;
ADS126xWriteRegister(IDACMUX, 1, &WriteRegData);
//((IDACMAG)) IDAC2 = IDAC1 = 1500uA
WriteRegData = (AdcRegData[((IDACMAG))] & ~(MAG2_MASK | MAG1_MASK)) | MAG2_1500uA | MAG1_1500uA;
ADS126xWriteRegister(IDACMAG, 1, &WriteRegData);
//MODE2 (BYPASS OFF, GAIN = 1 V/V)
switch(gain)
{
case 1:
gainBit = 0x00;
break;
case 2:
gainBit = 0x10;
break;
case 4:
gainBit = 0x20;
break;
case 8:
gainBit = 0x30;
break;
case 16:
gainBit = 0x40;
break;
case 32:
gainBit = 0x50;
break;
}
WriteRegData = (AdcRegData[MODE2] & ~(DR_MASK | GAIN_MASK)) | DR_20_SPS | gainBit;
ADS126xWriteRegister(MODE2, 1, &WriteRegData);
//Reset OFCAL coefficients
WriteRegData = 0x00;
ADS126xWriteRegister(OFCAL2, 1, &WriteRegData); //OFCAL2 = 0x00
WriteRegData = 0x00;
ADS126xWriteRegister(OFCAL1, 1, &WriteRegData); //OFCAL1 = 0x00
WriteRegData = 0x00;
ADS126xWriteRegister(OFCAL0, 1, &WriteRegData); //OFCAL0 = 0x00
//Reset FSCAL coefficients
WriteRegData = 0x40;
ADS126xWriteRegister(FSCAL2, 1, &WriteRegData); //FSCAL2 = 0x40
WriteRegData = 0x00;
ADS126xWriteRegister(FSCAL1, 1, &WriteRegData); //FSCAL1 = 0x00
WriteRegData = 0x00;
ADS126xWriteRegister(FSCAL0, 1, &WriteRegData); //FSCAL0 = 0x00
//电阻测量
//INPMUX (AINP = AIN1, AINN = AIN2)
WriteRegData = MUXP_AIN1 | MUXN_AIN2;
ADS126xWriteRegister(INPMUX, 1, &WriteRegData);
//REFMUX AIN4 AIN5
WriteRegData = RMUXP_AIN4 | RMUXN_AIN5;
ADS126xWriteRegister(REFMUX, 1, &WriteRegData);
//Read one conversion
set_adc_START(1);
WaitForDRDY();
set_adc_START(0);
AdcOutput = ADS126xReadData(6, 1);
resistance = ((double) AdcOutput / gain) / 2147483640.00f * 2.00f * 820.00f;
return resistance;
}