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ADS1241 采样值异常

Other Parts Discussed in Thread: ADS1241

各位好:

    如下图所示,我们采用ADS1241采用AVDD=5V,Vref=2.5V,AIN5引脚的待测量信号为0~5V,AIN6为2.5V基准电压,用于测量-2.5V~+2.5V的应用场景    

 

 

源码初始化步骤如下:

ba_ads_writeReg(ADS1241_SETUP, 0x00) ;  //PGA=1

ba_ads_writeReg(ADS1241_MUX, 0x56);  //AIN5+, AIN6-

ba_ads_writeReg(ADS1241_ACR,  0x00);  //Bipolar、RANGE=±VREF、DR=00(30Hz)

ba_ads_writeCmd(ADS1241_SELFCAL);  //失调和增益校准

。。。。等待6个DRDY周期

读取OCR=0x000101, FSR=0F0701

......

DRDY就绪后调用RDATA命令读取AD采样值

AIN5=3.111V时,AD值为0x1FD81F,在稍大些时,AD采样值变成从0x000000开始

请问是什么原因导致这个现象?