issue with SPI COMMUNICATION WITH AD7173-8, controller ESP32

Question

Hello everyone, 
 I am writing a driver to interface AD7173-8 to ESP32 Microcontroller. when I try to read the reset value of a particular register, it is giving different value. 
 here are the register reset values I tried to read 
 the status register reset value as per the datasheet is 0x80. but the reset value I read is 0x81. 
 the ADCMODE register reset value as per the datasheet is 0x2000. but the reset value I read is 0x201. 
 the IFMODE register reset value as per the datasheet is 0x0000. but the reset value I read is 0x01. 
 
 please help to tackle this issue. 
 thank you

JCCillion · Accepted Answer

HI SRISUS , 
 The ADC should be able to read +-2.5V. Note that the absolute input voltage of the ADC is AVSS-0.05 to AVDD1+0.05 for disabled input buffers and AVSS to AVDD1-1.1 for buffers enabled and ensure that the differential input voltage range of the selected positive and negative input pins is +/- Vref, wherein Vref = REF+ - REF-. In your case, for the split supply, Vref = 5V. This is also applicable when connected in single-ended configuration. 
 Yes, single-ended connection is able to read bipolar signals. Single-ended configuration means that you only have one input while the other input is fixed to ground. When bipolar mode is set, the ADC is able to accept a differential voltage either positive or negative. 
 Please use this equation to convert the output code. 
 Bipolar code: 
 Vout = [(Code/2^23) -1] * Vref 
 Unipolar code: 
 Vout = (Code * Vref) / 2^24 Regards, 
 JC)

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issue with SPI COMMUNICATION WITH AD7173-8, controller ESP32