ADS1294R: 通道输入配置为测试信号,采集的幅值均与预期不符

Part Number: ADS1294R

硬件是自己做的板子。使用菊花链方式连接了两片ADS1294R。AVDD=5V,DVDD=3.3V,外部时钟,内部基准,VREF配置为4V。

输入配置为直流测试信号时,
CONFIG2 = 0x13
CH1SET = 0x15
CH2SET = 0x15
CH3SET = 0x15
CH4SET = 0x15

采集输出原始AD值(转换成10进制数据):
1代表第一片ADC,2代表第二片ADC

1:CH1:-1991, CH2:-2259, CH3:-2278, CH4:-1596
2:CH1:-1325, CH2:-2786, CH3:-1737, CH4:-2320

根据手册,测试信号配置为 1 × –(VREFP – VREFN)/2400V 时,输出对应AD值应该为-3495左右。上面测试的结果与理论值相差较大。
另外,每个通道间也相差较大。按理说都是输入测试信号,每个通道采集的结果相差不应该这么大。

麻烦请教下,是哪里寄存器配置出现问题吗?

下面是完整的寄存器配置:
gREG_ST.m_CONFIG1 = 0x86;//速率500SPS,HR模式,菊花链模式
gREG_ST.m_CONFIG2 = 0x13;
gREG_ST.m_CONFIG3 = 0xE0; //4V参考,关闭RLD
gREG_ST.m_RLD_SENSN = 0x00;
gREG_ST.m_RLD_SENSP = 0x00;
//禁用导联脱落
gREG_ST.m_LOFF = 0x00;
gREG_ST.m_LOFF_SENSP = 0x00;
gREG_ST.m_LOFF_SENSN = 0x00;
gREG_ST.m_CONFIG4 = 0x00;
gREG_ST.m_LOFF_FLIP = 0;
gREG_ST.m_CH1SET = 0x15;
gREG_ST.m_CH2SET = 0x15;
gREG_ST.m_CH3SET = 0x15;
gREG_ST.m_CH4SET = 0x15;
gREG_ST.m_RESP = 0x20;
gREG_ST.m_WCT1 = 0;
gREG_ST.m_WCT2 = 0;
gREG_ST.m_GPIO = 0xFF;